Switch to Metric? Yes or No

[Bill Space]

Hi.

In a recent thread I remember someone saying "I just switched to metric and I am lovin' it " (Jim Becker maybe?)

That got me thinking. I am familiar with the metric system. But not sure what there is to Love about switching to it.

If I am making multiple pieces I use stops of some kind, so the initial measurement once done is irrelevant. If I am making something to fit somewhere I use sticks to determine the distance and make my cut accordingly. Metric or Imperial does not come into play.

So is there something that make the switch to metric, in countries (or is that Country?) that do not use it, that is a real game breaker?

As an aside, I have this really stupid Harbor Freight tape measure that is metric on one side and imperial on the other. What a crazy idea! I hate it.

So to those of you who have switched, is there something that makes the metric system superior for us in the US that still have 4x8 plywood and lumber dimensioned in inches and feet?

Bill

[Bruce Page]

No for me. As a one time machinist my mind always thinks in 3-place decimals. I can work in metric, it’s just not as effortless. Old dog, new tricks.

[Jim Becker]

Yes, that was me. And I remain committed to it wherever it's practical. There will still be some situations when inches will have to come into play, but I'm really finding metric to be so much easier for layout. And honestly, the size of a full piece of plywood really doesn't matter...in fact much of what I buy is slightly oversize anyway and pretty much all of it is in metric thicknesses. In reality, it doesn't matter what system you use as long as the end-result is accurate, however... :)

I also can appreciate Bruce's comments...as someone who has worked extensively with a different system for so long in a profession that involves measuring, moving to something else isn't all that practical. For me...that was not the case. None of my work in the 38 years I spent in the full time workforce required any kind of measuring. Well, perhaps the two years I was in the insulation contracting business, but that wasn't, umm...setup for any kind of close precision. :)

[Alex Tonin]

You're still safe to say countries, as Burma and Liberia are still not on board :)

I've lived outside the US for most of my life and find the conversions very difficult, especially when things get small. Not having anything smaller than an inch gets quite confusing for us foreigners :) Even 1/16" is about 1.6mm, and I work for a company where measurements shorter than that can be important. I am adjusting to try to convert on the fly with a decent approximation.

[Jamie Buxton]

Switching from inches to centimeters doesn't bring much benefit to me. But switching from fractions to decimals is a huge benefit. Doing math in fractions is difficult and error-prone. So I work in decimal inches.

[Tony Pisano]

Spent my working career as a machinist and I'll take thousandths and ten thousandths of an in any day.

[Ted Derryberry]

Yes, that was me. And I remain committed to it wherever it's practical. There will still be some situations when inches will have to come into play, but I'm really finding metric to be so much easier for layout. And honestly, the size of a full piece of plywood really doesn't matter...in fact much of what I buy is slightly oversize anyway and pretty much all of it is in metric thicknesses. In reality, it doesn't matter what system you use as long as the end-result is accurate, however... :)

I also can appreciate Bruce's comments...as someone who has worked extensively with a different system for so long in a profession that involves measuring, moving to something else isn't all that practical. For me...that was not the case. None of my work in the 38 years I spent in the full time workforce required any kind of measuring. Well, perhaps the two years I was in the insulation contracting business, but that wasn't, umm...setup for any kind of close precision. :)

Bruce and Jim, y'all bring up a good point that I hadn't considered before. I've been working with feet and inches almost on a daily basis since I was 9 years old. It's over 40 years now. What's the point of changing at this point? I could work in metric if I had to, but I don't. Also, as I've mentioned before, my customers order in inches. Converting would like just lead to errors. If I were building stuff just to suit me then it wouldn't matter. I got a CNC about 8 years ago and that's when I started using calipers and decimals in the shop.

[Malcolm Schweizer]

I lofted plans for a 6m sailboat that were in metric a few years ago and I was wishing all boat plans were in metric. It was a dream. Lofting in imperial units requires crazy fractions.

I grew up with both systems, so I “think” in metric, and that is the key to making the switch- you need to start thinking in metric. Can you visualize a kilo of dry goods, a decimeter width of wood, or a liter of a liquid? It helps if you have the visualization.

[Jerome Stanek]

Bruce and Jim, y'all bring up a good point that I hadn't considered before. I've been working with feet and inches almost on a daily basis since I was 9 years old. It's over 40 years now. What's the point of changing at this point? I could work in metric if I had to, but I don't. Also, as I've mentioned before, my customers order in inches. Converting would like just lead to errors. If I were building stuff just to suit me then it wouldn't matter. I got a CNC about 8 years ago and that's when I started using calipers and decimals in the shop.

You can use metric just as easy as inches on a CNC I have to use both at times I think metric is easier and I have been using inches for almost 70 years. My CNC is set up for inches but the one where I used to work was in metric. Also my laser is metric and I use the same software for both CNC and laser Vectric Aspire it converts both ways. When I was installing fixture for CVS drug stores they used Lozer and Ontario Store Fixture. Lozer was inches and OSF was metric. When I set OSF I had to allow more space as it was just a little larger than lozer.

[Ted Derryberry]

I know I could use metric on the CNC. I was just commenting that the CNC prompted me to refine my accuracy from 1/32" to 0.001".

I still think in fractions and know the decimal equivalents by heart.

To complicate things when I was a commercial superintendent I had to work in feet and inches for the building and feet and hundredths (as 1/100th of a foot, roughly 1/8") for the site work. There was always some overlap to keep things interesting too.

[Ken Fitzgerald]

The medical field converted to metric long ago. During my 34 year professional career, I used metric daily.

I actually have a non-HF tape that I used at work that has both metric and Imperial on it. I liked it, broke one and bought another one as a replacement.

[Jim Becker]

I forgot about the tape mentioned in the OP...I don't have a dual-purpose tape measure, although if I get involved in any install work for things I produce in the future, I may get one for that particular purpose for convenience. Right now, for metric, I use a metric tape (Veritas) and for Imperial, I use an Imperial tape (Stanley). My metal rules, however, are inches on one side and metric on the other. Fortunately, the metric side is generally the most convenient for the way I measure things. :) I got new rules for my Starrett combination squares that are just metric, but I keep one additional square with the "good" Starrett Imperial rule in it, too, for convenience. I'm thinking about getting the 600mm Woodpeckers layout tee square at some point...'may ask for it for my birthday. :)

[Bill Dufour]

I did find that metric is the way to go when working on cars. Trying to center a seat base on an existing hole pattern got a lot easier when I realized the patterns were both metric. years ago I mounted fog lights on a Volvo Bumper and using metric to align them equal distances apart convinced me.
I believe Ford switched from inches to metric dimensions for most body parts by the model T in 1909.
Bill

[Martin Wasner]

There's two kinds of countries. Those that put a man on the moon, and those that use the metric system....

It's a stick. Nothing more. I use imperial in decimal and fraction. I also use SI. There's no difference, just a stick. I can run fractions in my head way easier than decimals though.

My only problem with SI is having a single unit of measure. That's a bizarre concept to me.

[Chris Parks]

The conversion in the US will happen because industry has to use metric to trade with other countries. In some ways you could say the conversion has already gone a long way down the road not just at the level the average person operates at. I am building a chair at the moment in imperial measurements and I found it surprising how easily I found it not having used Imperial measurements for over 30 years and being forced to convert when the plans I received to build my shed were all in metric. I detest fractions and anything to do with them, they are a clumsy calculation that promote errors and should be binned as a measurement and decimals used. I think it is advisable if changing not to convert, forget all about it and work within the system you choose. I did not try and convert the imperial plan to metric, it simply does not work. I would suggest to anyone who is not sure about working in metric or criticises the idea to find a simple project in metric, pick up a tape or rule in metric and start from there. I find it so much easier than imperial due to being literally math challenged due to my short schooling life. I agree with the poster above, we tend to measure too much rather than use the project pieces to define the measurement no matter what system we work in.

[Ron Citerone]

I have worked in Inches for so long it's just easier for me, but could work metric if needed. For woodworking I will stick with inches until I find a real advantage to metric. They are all just numbers in the end.

[William Adams]

As I've noted in other thread, I've switched to metric for CNC work, but use Imperial for all hand work --- esp. if it involves dividing by thirds / sixths / twelfths, &c. If need be, I break out a desktop publishing points ruler to get 72 points per inch which pretty much always guarantees that distances will be some nice even number as opposed to the irrational values which dividing into thirds using metric usually results in.

[Chris Parks]

I have worked in Inches for so long it's just easier for me, but could work metric if needed.

Everyone in every country that has converted has said similar things including me. I don't know of anyone in Oz who has regretted changing systems.

[Pat Barry]

As I've noted in other thread, I've switched to metric for CNC work, but use Imperial for all hand work --- esp. if it involves dividing by thirds / sixths / twelfths, &c. If need be, I break out a desktop publishing points ruler to get 72 points per inch which pretty much always guarantees that distances will be some nice even number as opposed to the irrational values which dividing into thirds using metric usually results in.
What benefit do you see in using metric for CNC? I'm not seeing it.

The ONLY reason I'd switch would be for some as yet unidentifiable customer or material reason.

[Wayne Lomman]

As I may (well, certainly) have mentioned some time back, the country that put men on the moon did not do it alone. That county's eyes and ears for half the time were on the other side of the globe. So please don't trot out irrelevant excuses.

More to the point, use whatever system you want. Australia changed systems as a nation when I was in school. We all got over the shock, and the sky didn't fall on our heads. I learnt both systems and understand both systems but use metric because that is the official system. It's like I speak English because that is our official language but it doesn't stop me understanding Polish (especially the curses....!).

I believe the key to the change in Australia was that there was clear leadership with the issue. Also, Australia adopted units in multiples of 1000 ie microns, millimetres, metres and kilometres. Centimetres are not official and never appear on technical drawings. That way everything has up to 3 decimal places for each unit. If you want to go smaller than microns, be my guest.

We have an extensive range of CNC machining centres here. Most of our operators are in the 55-70 age bracket. They all learnt machining in imperial and much prefer working in metric.

I do recall my boss back in about '74 commenting how measurement errors dropped markedly when metric was introduced. That was in residential construction.Cheers

[mreza Salav]

There's two kinds of countries. Those that put a man on the moon, and those that use the metric system....


One of the most ..... comments I've read here.

[Ted Derryberry]

I work with Russian plywood all the time and it's definitely metric. 18 mmish by 1220 mm by 2440 mm. Says so right on the label. Now grab your calculator and see if it's the supplier or the consumer that's determining the size of the "metric" plywood.

I've run into all kinds of stuff in construction that's "metric" but when you convert you find that it's based on an imperial standard. Not just construction either. If you know anything about firearms you've heard of the AK47 round which is 7.62x39. That's a bullet diameter of 7.62 mm. Guess what that converts to. 0.300", which is "30 caliber".

Since base 10 is so much better when are we all going to change our method of telling time?

[Ted Derryberry]

One of the most ..... comments I've read here.

Accurate??

[Steve Demuth]

For woodworking measurements, which are almost all about length, I am pretty indifferent - either works equally well for me. Sometime the binary fractions are handier, sometimes the decimal. If, for example, I am working a Golden Ratio in a design, or need to subdivide a length by anything that isn't a power of 2, I use metric for ease of calculation. For most woodworking measurements, though, decimal has no particular advantage. As a result, I sometimes use both on the same project. For everything else, the SI measurements make so much more sense because of the overall logic of how the different measurements relate. I of course use the Imperial measurements for volume and weight to buy food and gasoline, because that's how stuff is packaged and sold for the most part. But I'd prefer metric, and I do everything involving any physics more complicated than volume in SI.

[Walter Plummer]

I agree it does not matter which system but choose one for the job and stick to it. The problems start with "what's metric for 15/32?"

[Doug Garson]

I agree it does not matter which system but choose one for the job and stick to it. The problems start with "what's metric for 15/32?"
and ends with what's imperial for 12mm?

[Lyndon Klassen]

I recently did a construction job (about a year worth of work) that had metric plans. The only place we really measured in metric was for the block walls. 40cm per course, couldn't do the conversion on my head for more than one course. Then we switched over immediately to a job with imperial measurements on the plan. I'm not going to lie, it took some focus to mentally switch gears.

[Glen Gunderson]

When doing cabinets, I use metric almost exclusively. Decimal inches are a close second, but I've given up on fractions for anything where I need to add and subtract a bunch of numbers (overlays, reveals, etc.). Too much time and too many errors.

I do find mm a little easier and little more intuitive than decimal inches. Maybe because it's a completely different system whereas with inches I keep reverting to trying to think in terms of fractions.

For furniture, I'll use either system. Sometimes it's inches for the conceptual stuff and then mm and story sticks when it comes time to build, or sometimes all inches.

[Rich Engelhardt]

My $19.99 Harbor Freight Imperial/metric/decimal/fractional caliper makes switching back and forth just a simple matter of touching a button ;)......plus...it measures things too!

[Derek Cohen]

I use both systems, and often use them alongside one another ... that can be confusing for some who read my notes!

Metric is definitely easier when one has to add together what otherwise would involve fractions. For example, 2.5mm + 2.75mm vs 2 1/2" + 2 3/4".

Metric is easier when working from my European machines, especially the thicknesser (planer), which is Metric. It does not make any difference with the Festool Domino machine, since an exact position (in numbers) is not important.

Imperial raises its head because I must allow for the fact that all my hand tool joinery planes and chisel blades are in Imperial (e.g. plough plane, router plane, mortice chisels, dado plane).

Also, it is easier to visualise 6 feet than 1828.8mm or 1.828m!

My tape measures contain both sets of numbers.

Much of the time tape measures are for rough work anyway. Most of my measuring is done with a cutting gauge or from parts.

Regards from Perth

Derek

[Jerome Stanek]

What benefit do you see in using metric for CNC? I'm not seeing it.

The ONLY reason I'd switch would be for some as yet unidentifiable customer or material reason.

I ran a Biesse pod and rail and it is metric. the readouts to set the pods are easier to set in metric as everything is based on 10s

[Martin Wasner]

One of the most ..... comments I've read here.


Using a SI keyboard I see...



If the second part of my post didn't make the first part of then post obvious, I can't help you.

IT'S A STICK! The Imperial system just has different sticks to choose from. Mixing a meter in with the inch/foot/yard/rod/mile doesn't matter.

Just because something is 12-3/8 inches long doesn't change the fact that it is .314325 meters, or 1.03125 feet, or .0002 of a mile. It's still the same length. Some units are easier than others. Some things it doesn't even matter. Does it make any more sense that one light year is 5.879e+12 miles, or 9.461e+15 meters? (I had to google that one) For volumes, and converting to weight of water, metric is way easier because the system was built around it.

To put it plainly, SI was designed for the science community. The imperial system worked it's way out of a few thousand years of human relation to the body and environment. The inch is similar to the rule of thumb. The foot is pretty obvious. The yard is the human pace.

It's like saying The Swedish Krona is worth more than the Mexican Peso. Nope. It just takes more Pesos to buy a Volvo, but that Volvo has the same value no matter what.



To the OP, make the switch. It doesn't change anything. 3/8 of a meter is still .375m or 14-3/4"

[Curt Harms]

The conversion in the US will happen because industry has to use metric to trade with other countries.

That will be the driver, I think. I get along OK with metric distance and weight but KW and Newtons are still difficult.

[William Adams]

For me, the advantage to switching to metric for CNC was that a couple of the early hobbyist communication / control programs were metric only, so one pretty much had to switch.

I also had to work up a bunch of feed / speed charts, and I just found it easier to standardize on one style of unit, and on the smaller hobbyist machines, the finer units allow at least the illusion of more control.

So, I draw up a file in Imperial, open it in my CAM program, set the stock size using Imperial, then switch the program to metric and finish it out --- the app doesn't care about the bizarre decimals, and as long I don't have to deal with them too directly, I'm able to cope as well.

[Malcolm McLeod]

...
IT'S A STICK! ...

^Exactly. People are resistant to change because they are CONVERTING (sorry, didn't mean to shout).:o

Mr. Schweizer has it nailed, as it is about visualization: If someone tells you to cut about 250mm off of the end of a board, do you spend 4-5 minutes converting to fraction inches? Or, do you grab a saw, 'visualize' that you need a piece slightly wider than the span of spread open human hand, and whack it off. Done!

How long to drive 100km on the freeway (non-LA)? 4-5 minutes converting..? Or do you just blurt out, "about an hour"?

I work in imperial, just because I'm accustomed to it and all my 'sticks' are such, but I hate combining or comparing fractions (quick, is 17/32" more or less than 33/64":confused:). And every time I see this and related topics, I resolve to go buy new measuring 'sticks'.

(IMHO +/- 1mm is probably accurate enough for 80% of the woodwork done, and +/- 0.1mm gets the next 19.99%.)

[Rod Sheridan]

That will be the driver, I think. I get along OK with metric distance and weight but KW and Newtons are still difficult.

Curt, weight is in Newtons, as it's a force. The pound is also a unit of force, not mass.

The unit of mass is the gram (or Kilogram), or in the imperial system the unit of mass is the slug.

Canada went metric in the seventies, and for me, science has always been metric as I was in post secondary in the seventies.

At home I switched to metric about 20 years ago for wood working. I find it much easier to design in metric as nobody cares if my furniture has a 3/4" thick board or a 20mm thick board.

Same for table legs, do you care if they're 50mm or 2"? Design is so much easier in metric, when I bought my new shop equipment I specified all metric gauges, makes stuff really easy. Need a 20mm thick piece? Set the planer to 20mm and that's what you get. Need an 823mm long piece? Set the crosscut fence to that and away you go.

Regards, Rod.

P.S. Curt, with all that said, I often see forms with a space for your body weight in Kg or pounds, some further education required:rolleyes:

[Robert Engel]

I've never switch to metric, but I use it all the time when dividing or spacing out something.

[rudy de haas]

Metric is easier to use for most people most of the time. However...

1 - fractions are more precise than decimals. 2/3 is precise; 0.666666 etc etc is not.

2 - the metric systems' claimed logical link to physical reality (e.g.length of the meter as a decimal fraction of the earth's diameter at the equator) is illusory b.s. For the most part the measurements aren't accurate and the claimed relationships more a matter of virtue signallng than reality.

3 - there is a possible ( very hypothetical at this point) deep complication - use of imperial measure is more demanding than use of metric (for simple measurements like inches vs centimeters). Excercising the brain pays off - 1/2" is not smarter than 12mm; but it is more precise and you do have to use your brain a bit more to work with it. There is now some evidence that many 2nd and 3rd generation asians who are genetically identical to 1st and 2nd generation do worse on standardized IQ and aptitude tests than their predecessors and the probable cause for this is that they don't learn to speak, read, and write chinese (or whatever) along with English. i.e. that the complexity of language use excercises the brain and pays off in other skills. Use of imperial vs metric may work the same way simply because it is harder to work with fractions and unrelated (arbitrary) measures.

[Jim Becker]

People are resistant to change because they are CONVERTING

Honestly, this is the crux that I found in this journey...stopping the "converting" and just measuring. The challenge behind that is mental visualization still has to catch up since I and many others "grew up" visualizing in different units of measure. I'm slowly but surely getting there. In some respects, it's a little like learning another spoken language...human nature has us "mentally translating", slowly at first, and over time as we become "fluent" we begin to be able to think in the alternative language. Some folks are more suited to this and other's take longer. Ultimately, however, almost anyone will get there via immersion. So my bottom line is that if one wants to embrace metric...do it by committing to it. That immersion is important to move beyond the "conversion/translation" phase and into just thinking in that new system/language.

[Paul Girouard]

If you’re doing it for a hobby have at it. If you are in the trades forget it, it’ll cost you money every day. Few trades people talk or use metric , so if you think you’re going to change the world , good luck to ya!

[brent stanley]

There's two kinds of countries. Those that put a man on the moon, and those that use the metric system....


NASA uses metric....the Appolo guidance equipment was programmed in SI.

[William Adams]

The control panels for the L.E.M. at least read out in Imperial measure.

[andrew whicker]

So then you buy all metric drill bits, metric router bits, etc? If you have to use a vendor, do you convert everything back into Imperial?

Fractions do suck. I have a 12" engineer ruler that spaces each inch with 10 spaces. That's a quick way around the metric problem, sort of. You would really need an inch divided into 20 spaces to get the precision you may want. (1/16" = .064" & 1 mm = .039")

[mreza Salav]

Using a SI keyboard I see...



If the second part of my post didn't make the first part of then post obvious, I can't help you.

IT'S A STICK! The Imperial system just has different sticks to choose from. Mixing a meter in with the inch/foot/yard/rod/mile doesn't matter.

Just because something is 12-3/8 inches long doesn't change the fact that it is .314325 meters, or 1.03125 feet, or .0002 of a mile. It's still the same length. Some units are easier than others. Some things it doesn't even matter. Does it make any more sense that one light year is 5.879e+12 miles, or 9.461e+15 meters? (I had to google that one) For volumes, and converting to weight of water, metric is way easier because the system was built around it.

To put it plainly, SI was designed for the science community. The imperial system worked it's way out of a few thousand years of human relation to the body and environment. The inch is similar to the rule of thumb. The foot is pretty obvious. The yard is the human pace.

It's like saying The Swedish Krona is worth more than the Mexican Peso. Nope. It just takes more Pesos to buy a Volvo, but that Volvo has the same value no matter what.



To the OP, make the switch. It doesn't change anything. 3/8 of a meter is still .375m or 14-3/4"

That comment was (at best) irrelevant. So is the rest of the comment given here.
Just because something has been in use for many years or people are used to it doesn't mean it is easier to use. I am sure using horses to go from point A to point B has been in use for thousands of years.

It is obvious whatever system you use an inch is still an inch. The question is which system is easier to work with. If you find adding/subtracting and multiplying fractions easier than decimal good for you. For most people, calculating how much would be 12 times 2 9/16 will take longer than calculating 12 times 65mm (if you work within 1/16 or about 1mm accuracy these two distances are about the same).

[Ted Derryberry]

I guess they don't have those new fangled calculators in Canada yet.

[Steve Peterson]

There's two kinds of countries. Those that put a man on the moon, and those that use the metric system....

That is a great quote.

My biggest issue with conversion is the sheer bulk of imperial rulers in my shop. The rules on my tablesaw fence, hand wheels on the metal lathe, more than a dozen tape measures, squares, calipers etc. The complete list would go on for several pages. It would be awkward to be partially switched to metric, so all of them would need to be switched.

I do use metric in a few applications. Some default to cm, others use mm, others use microns or meters. I still have to be aware of which metric scale to use. It seems like I am often scaling between cm and mm. Sure, the conversion is easy, but it is also easy to forget and end up with a size that is 10X larger or smaller than expected. This error rarely occurs with imperial measurements. Construction is always in feet and everything else is always in inches.

[brent stanley]

The control panels for the L.E.M. at least read out in Imperial measure.

Yup, it was converted for the operators.

[Martin Wasner]

For most people, calculating how much would be 12 times 2 9/16 will take longer than calculating 12 times 65mm (if you work within 1/16 or about 1mm accuracy these two distances are about the same).

My hat is off to you if you can do that in your head in either scenario. But switch it around and rearrange the math. 12x2.5625, or 12 x .065. In this odd case, I can start wrapping my head around swapping the meter into a fraction, 1/16 in this case, and actually get pretty close in my head if I'm just looking for a ballpark. 12/16, or basically .75m. I have to grab a calculator to get the actual which is .78. So I'd be off by 30mm with my ballparking. For me to do 12x2.5625 I have to compartmentalize it, (12x2=24)+(12x.5625) well thats kinda 12x.5=6, so I'm up to 30+(12x.0625). 12/16 is 3/4, so 30-3/4" I did that in my head and double checked it with the calculator.

Real world application though. You've got a 24-3/8 opening that is getting a pair of doors with a 1/2" overlay and a 1/8" margin between the doors. 24-3/8+7/8=25-1/4 then divide by 2 for the pair and you get 12-5/8. That's easy mental math that doesn't require a calculator at all.

Call that opening .62m with a pair of doors with a .013m overlay, and a .003m margin between the doors. .62-.023=.597 Then divide by two to get the door size which is .2985m I still got there without a calculator, but it took me a second longer.




For doing math mentally, being able to break the things before and after the decimal into two parts makes it easier for me. When I can break meters into fractions that makes me happy because I know that .375m(3/8)+.5625m(9/16)=.9375(15/16)m. A base 2/4/8/16 system is really easy to wrap your head around. Erratic and base ten fractions are the devil though and I can't wrap my head around the math very easily because I'm not familiar with the numbers like I am on the regular carpenter fractions.



The thousands of years comment is because the units come from things that are used day to day. That's the history of the units and where they came from. I don't know anyone that uses the circumference of the earth in a day to day at all. But from post agriculture to the pre-industrial revolution it gave people units to get close enough on most things. (That is unless of course your into building massive megalithic structures precisely laid out with sacred geometry, that's a different/fun topic all on it's own)


Both have their place, I use both, so in my view there's no advantage to either. I work in the trades, so I'll likely get puzzled looks for explaining things on prints to contractors in meters though. But in a shop full of metric machines and using european hardware, I have to think in both.

I was explaining to a guy I was interviewing recently about doing math in your head quickly was kinda like knowing your phone number. You don't figure out your phone number, you just know it. When you've added certain numbers together for so many years they become like your phone number, you just know that 1/4+3/8=5/8.

[Martin Wasner]

I still have to be aware of which metric scale to use. It seems like I am often scaling between cm and mm.


Just do it all in meters. That's the only unit anyways, why mess with a decimal point and a word.

Mille - 1000th
Centi - 10th
kilo-1000

I worked in a cabinet shop for a while that used feet and inches. Traditionally cabinet shops run purely in inches, anything else confuses our poor simple minds, but the dude doing producing all of the shop drawings was an architect and wanted us in his system. It caused some problems for me when glancing at a print and seeing 2' 3-11/16" as 23-11/16". Which are not the same at all....

[Glen Gunderson]

For cabinetmaking I find sticking with mm much easier. Using the numbers in Martin's post above, combining a 620mm opening + two 13mm overlays - 3mm gap and then ÷ 2 to arrive at 321.5mm for each door is easier for me than using .62m, .026m, and .003m. The decimal and having to think about how many places are after it just makes it slightly more awkward. And of course if you're doing cabinets you don't need to go through all the steps each time, you can just remember to add 26mm to the opening for single door cabinets and 23mm for two door ones when using that overlay and gap.

And in comparison to fractions it's so much easier. 22 11/16" + 7/8" ÷ 2 for instance isn't something I can do very quickly in my head, though maybe that's because I don't do it that often. And even if it does only add a few seconds for each measurement, it's more error prone for me at least. I make mistakes far more often when doing that kind of thing with fractions than I do with mm or decimal inches.

[mreza Salav]

My hat is off to you if you can do that in your head in either scenario. But switch it around and rearrange the math. 12x2.5625, or 12 x .065. In this odd case, I can start wrapping my head around swapping the meter into a fraction, 1/16 in this case, and actually get pretty close in my head if I'm just looking for a ballpark. 12/16, or basically .75m. I have to grab a calculator to get the actual which is .78. So I'd be off by 30mm with my ballparking. For me to do 12x2.5625 I have to compartmentalize it, (12x2=24)+(12x.5625) well thats kinda 12x.5=6, so I'm up to 30+(12x.0625). 12/16 is 3/4, so 30-3/4" I did that in my head and double checked it with the calculator.

Real world application though. You've got a 24-3/8 opening that is getting a pair of doors with a 1/2" overlay and a 1/8" margin between the doors. 24-3/8+7/8=25-1/4 then divide by 2 for the pair and you get 12-5/8. That's easy mental math that doesn't require a calculator at all.

Call that opening .62m with a pair of doors with a .013m overlay, and a .003m margin between the doors. .62-.023=.597 Then divide by two to get the door size which is .2985m I still got there without a calculator, but it took me a second longer.




For doing math mentally, being able to break the things before and after the decimal into two parts makes it easier for me. When I can break meters into fractions that makes me happy because I know that .375m(3/8)+.5625m(9/16)=.9375(15/16)m. A base 2/4/8/16 system is really easy to wrap your head around. Erratic and base ten fractions are the devil though and I can't wrap my head around the math very easily because I'm not familiar with the numbers like I am on the regular carpenter fractions.



The thousands of years comment is because the units come from things that are used day to day. That's the history of the units and where they came from. I don't know anyone that uses the circumference of the earth in a day to day at all. But from post agriculture to the pre-industrial revolution it gave people units to get close enough on most things. (That is unless of course your into building massive megalithic structures precisely laid out with sacred geometry, that's a different/fun topic all on it's own)


Both have their place, I use both, so in my view there's no advantage to either. I work in the trades, so I'll likely get puzzled looks for explaining things on prints to contractors in meters though. But in a shop full of metric machines and using european hardware, I have to think in both.

I was explaining to a guy I was interviewing recently about doing math in your head quickly was kinda like knowing your phone number. You don't figure out your phone number, you just know it. When you've added certain numbers together for so many years they become like your phone number, you just know that 1/4+3/8=5/8.

First of all, I work with both systems and oddly enough,mostly imperial because my tooling is mostly imperial and so it becomes tricky to convert back and forth).
Secondly, Yes I do all the math in my head. I rarely (if ever) use calculator (honestly don't know where my calculator is and if it has battery!). I am fortunate enough (and not old enough yet!) to be able to do these faster than using a calculator.
As for your example and numbers you gave, they look odd because you are still fixing your head to work in the imperial system and numbers coming from there. If you are working with metric system and going with the example you mentioned for doors you can simply design it in the metric and everything will be a whole simple number in metric. European tools/hardware are all metric and I don't find them difficult to work with at all. True, powers of two (1, 2, 4, 8, 16, etc) is good if everything you do is going to be multiplied or divided by two. But as soon as you want to divide/multiply things by factors other than two or you want to even add two fractions with different denominator (8 11/16 + 23 5/8) it slows you down.

Anyway, each one to his own.

[Keith Outten]

No metrics for me...EVER.

Concerning NASA I was the QC Inspector on the Space Shuttle Engine test stand my company built in the early 1970's and all of the drawings used imperial measurements. I was the project inspection coordinator at NASA Langley for ten years inspecting all of the wind tunnels and high pressure piping systems. All of the drawings we were provided and those we created used imperial measurements.

I worked on several submarine and aircraft carrier hulls at Newport News Shipbuilding, everything was done using imperial measurement. I worked on construction projects for nuclear power plants, fossil fuel plants and a host of our large projects from Carolina to New York state, they all used imperial measurements.

If it ain't broke don't fix it :)

[Malcolm McLeod]

..True, powers of two (1, 2, 4, 8, 16, etc) is good if everything you do is going to be multiplied or divided by two. But as soon as you want to divide/multiply things by factors other than two or you want to even add two fractions with different denominator (8 11/16 + 23 5/8) it slows you down.

Anyway, each one to his own.

^Agree.

You can skew the decision in any direction you want if you cherry pick your example math:

Half of 19mm = 9.5mm (hard) or half of 1/2" = 1/4" (easy)

1/3 of 30mm = 10mm (easy) or 1/3 of 1/2" = 1/6" (easy too) - -until you grab a ruler...so lemme think ... that's about roughly ballpark approximately 5/32" = close enough.

[Ted Derryberry]

32-5/16"...........

[Cary Falk]

I work with metric at work(nanometers, angstroms,microns, g/L, Celsius, etc.) I prefer to work with inches and feet in the shop because I can visualize those measurements. Almost all of my shop is set up for inches. I like working with fractions. Metric won't get rid of fractions though.

[andrew whicker]

I don't have any numbers to back this up, but I'm guessing US switching to metric is more earth shaking than Australia. Contrary to popular belief, US manufacturing output increases every year (jobs within manufacturing may be a different story). And I'm willing to bet that most of those shops are full of Imperial cutters, drills, wrenches, hardware, etc etc. I think the politics behind a major switch would be difficult. Let's just let the free world figure it out on their own instead of doing a forcing rule.

As was pointed out earlier, it seems major industries (like auto) have already or are in process of switching over anyway.

Also... the NASA quote... NASA? What NASA? I kid, but seriously, did anyone watch the awesome SpaceX launch yesterday? I wonder if they use metric.

[brent stanley]

No metrics for me...EVER.

Concerning NASA I was the QC Inspector on the Space Shuttle Engine test stand my company built in the early 1970's and all of the drawings used imperial measurements. I was the project inspection coordinator at NASA Langley for ten years inspecting all of the wind tunnels and high pressure piping systems. All of the drawings we were provided and those we created used imperial measurements.

I worked on several submarine and aircraft carrier hulls at Newport News Shipbuilding, everything was done using imperial measurement. I worked on construction projects for nuclear power plants, fossil fuel plants and a host of our large projects from Carolina to New York state, they all used imperial measurements.

If it ain't broke don't fix it :)
I expect they were capable of converting to imperial for the outside contractors if needed, but these days, it's public law to use metric in gvt programs.

https://www.nasa.gov/offices/oce/functions/standards/isu.html

Metric in the moon missions makes sense considering it was a bunch of Canadian aerospace engineers and German rocket scientists.

Ducking and running....

[Martin Wasner]

Isn't NASA in the Bahamas?.... lol

[Wayne Lomman]

Our drawing conventions based on the Australian version of the metric system never refer to .375m for example. That is always just 375. If a drawing calls for 24.466m it is written as 24466. For any drawing for a residential building or smaller structure down to cabinet work, everything is in millimetres. There is no 'mm' after every measurement on the drawing, just the raw number. There will be a reference on the information panel as to what the units are.

Machining drawings will be in millimetres to 3 decimal places. Civil works drawings will show decimals to 3 places. Then the main units will be metres but roadworks can be kilometres as well when the job is large enough.

The common thread is that every unit step or part thereof is a multiple of 1000 from microns right through to kilometres. It works the same for weight and volume as well. Cheers

[Steve Demuth]

If it ain't broke don't fix it :)

Arguably, it is broke. As I said earlier, if you're just building something in your home shop from wood, you're mostly using length, and in makes only marginal difference whether you use metric decimal, Imperial - with binary fractions, or inches decimal. I sometimes use 2 or three in a single project.

But one key value of a system of measurement is agreement between parties on how big, how much, etc - and Imperial is the odd ball on that. As long as you're completely local in the United States, it doesn't matter, but as soon as we're interacting with the rest of the world, Imperial is broken, because it's the different one and forces us into conversion land.

The other sense in which it is broken is if you're needs go beyond simple length and volume measurements. The metric / SI system is vastly easier to navigate for anything involving energy, power, force or related concepts, and is already the standard even in the United States for electrical measurements. The inter-relatedness of those units with the basic units of length and mass is greatly simplifying.

[Doug Garson]

It seems like I am often scaling between cm and mm. Sure, the conversion is easy, but it is also easy to forget and end up with a size that is 10X larger or smaller than expected. This error rarely occurs with imperial measurements. Construction is always in feet and everything else is always in inches.
If you end up with something that is 10x too big or small it would indicate that you don't have a basic feel for the size of the piece you are making. I'm old enough to have used a slide rule early in my career. If you misplaced the decimal point it meant you didn't have a good feel for what the answer should be. Last time I checked, stud spacing in construction was in inches not fractions of feet.
The only reason most people prefer the imperial system is that they grew up with it. Canada went metric a long time ago but I grew up with imperial so I am still more comfortable with it, I have nephews who grew up with metric and guess what? Even for me, driving distances are much easier to picture in metric despite my preference for imperial for woodworking. Why you ask? I can picture the length of a football field which is, approximately 100 metres long so a kilometer is about 10 football fields, Much easier to picture than 17.6 football fields.
The real source of errors is when converting between the two systems, to see a great example of this check out the Gimli glider, the pilot would give Sully a run for his money when it comes to extreme landings.
https://en.wikipedia.org/wiki/Gimli_Glider

[Mel Fulks]

Well, many times when employees "don't have a basic feel for the size of the piece they are making" , they might not even know
what they are making. Sometimes you don't get those details. I have refused to proceed with work where those details were not clear. I don't accept 'smart people don't need all the info'. And some things are made in different sizes. When the next Titanic film is made it will be important to know which model is 15 FEET and which is 1200 FEET.

[Bill Space]

My biggest issue with conversion is the sheer bulk of imperial rulers in my shop. The rules on my tablesaw fence, hand wheels on the metal lathe, more than a dozen tape measures, squares, calipers etc. The complete list would go on for several pages. It would be awkward to be partially switched to metric, so all of them would need to be switched.


I think Steve has hit the nail on the head. This was the conclusion I reached after reading everyone’s posts, before reading Steve’s comment. I have too many imperial tools to convert totally. Couple metal lathes and other machine tools as well as woodworking tools, measuring tools, and so on.

I guess for me converting would be mostly pain with little (if any) gain. :)

Thanks for the insight guys!

Bill

[Brian Holcombe]

I use both along with occasional use of Shaku.

[Mike Trent]

Several folks have commented about difficulties in conversion calculations, which can introduce errors. Pondering this, I thought to myself “Didn’t a jet run out of fuel in Canada, due in to an Imperial/metric conversion error? I seem to remember that.”

Google provided the answer. A perfect storm, including a conversion error, occurred, and an equally improbable number of serendipities allowed everyone to walk away.

https://en.m.wikipedia.org/wiki/Gimli_Glider

[Frederick Skelly]

All I'm gonna say is that the last time we had the english vs metric debate, I wrote down the following quote:

"The mile is based on a thousand paces, which is very handy if one wants to know how far he has walked. I will keep the metre in mind the next time I walk from the equator to the north pole."
- Warren Mickley

:D :D :D

[Doug Garson]

Several folks have commented about difficulties in conversion calculations, which can introduce errors. Pondering this, I thought to myself “Didn’t a jet run out of fuel in Canada, due in to an Imperial/metric conversion error? I seem to remember that.”

Google provided the answer. A perfect storm, including a conversion error, occurred, and an equally improbable number of serendipities allowed everyone to walk away.

https://en.m.wikipedia.org/wiki/Gimli_Glider

mmmmm, where did I hear that before, oh wait, post #61 Yes it was an incredible story :D

[Mike Kees]

As a Canadian I learned Metric in school. As a carpenter I use imperial all day long. Funny because when I travel to the states it seems to take so long to drive a mile,much longer than a kilometer. I do not know anyone who tells you their height and weight in metric it is always 6'2'', 220. I can't imagine buying gas in gallons here in Canada. Temperature really screws me up in Farenheit, I have no idea what 30 degrees Farenheit is. So at the end of the day we are supposed to be officially metric but in reality because the U.S. is our largest trading partner we are truly caught between two systems. As a carpenter I have worked on large jobs (goverment) where plans are Metric. We used the "bastard tapes" talked about earlier in this thread with both systems on them. You simply used the Metric to cut plates to length and layed out with 16''' centers. All our plywood and OSB is 4'x8' because we export so much to the U.S.I do not think that will ever change. When I was 18 I started buying mechanical tools,I remember asking my Dad if I should buy Standard or Metric. Ended up with both,still use both however Metric is slowly gaining ground .I do work mostly with Imperial measure in my shop.

[Chris Parks]

If you’re doing it for a hobby have at it. If you are in the trades forget it, it’ll cost you money every day. Few trades people talk or use metric , so if you think you’re going to change the world , good luck to ya!

The rest of the world and large parts of US industry have already changed. Witness the importation of metric sized products into the US. It will be a gradual erosion of the imperial system and take many years but it will happen for better or worse.

[Ted Derryberry]

Yeah, like the Russian plywood I mentioned that's 1220 x 2440. Do the math.

[roger wiegand]

I’m a scientist, so I think in metric and centigrade , but I avoid conversions at all costs. Too error prone. As is doing math in fractions. As is dividing units into eight or 12 parts rather than 10. Just the way my brain works. As a cook I appreciate being able to weigh out 300 g of water when the recipe calls for 300 ml (yes, I also do all my cooking by weight/mass rather than volumes, similarly for mixing epoxy, making up shellac, or dyes. Again, less chance for error and relatively easy precision. If you were learning from scratch I can’t imagine why you would choose to use the oddball English measures.

[Gary Radice]

I have the same background as Roger and I mostly agree with him. I can use either system but for me the issue is tooling. My shop has all imperial tooling (drills, measuring tapes, scales, blades, bolts, etc. The only SI stuff is machine bearings! So although I would prefer metric in the shop, the only time I need to use metric is when I buy plywood.

[Ted Derryberry]

Every lumber yard I've ever been to still sells "three quarter inch" plywood, even though it's 18 mmish. Why would you need to use metric? In fact, type in "3/4 plywood" on Home Depot's website and you'll get 55 results.

Today I was in the shop and caught myself using "fractions of a fraction". My tape only goes to 1/16" of an inch, but I work to tighter tolerances. I needed to cut a part that "should" have been 26-3/4", but when I checked it was actually a little over. In my mind I thought 26 inches and 12 and one half 16ths. :) Never been a problem for me.

The 12/16ths comes from being around commercial drywall and ceiling crews. They usually have one guy measuring and installing and another cutting. With ceiling tiles they work to the 16th and just call out the inches and 16ths, even if its an even number. For example "15 and 8" means 15-1/2". Everybody knows the system so there's no confusion and it cuts down on the number of numbers you have to say or hear on an often noisy construction site. Ironically most of the guys come from countries that use the metric system.

[Patrick Curry]

Strange as it sounds, I think the hardest part of switching from imperial to metric is visualizing the measurements. Imperial is native- it’s like thinking in English.

[Keith Weber]

It's like saying The Swedish Krona is worth more than the Mexican Peso. Nope. It just takes more Pesos to buy a Volvo, but that Volvo has the same value no matter what.

If you think a Swedish Krona is not worth more than a Mexican Peso, then I'm afraid you don't understand the concept of currency exchange. A Krona IS worth more than a Peso (approximately 2.32 times more). That's why it takes less Kronor to buy your Volvo.

[Grant Wilkinson]

I use both (or either), depending on what I am doing.

In Canada, we say that we "went metric" many years ago, but in reality, we just added metric to our long in use imperial system. We by 2 x 4 lumber and space them on 16" centers. We buy 4 x 8 sheets of plywood. But, we buy gas in litres and cold meat in grams. We measure temperature in Celsius, but we don't measure pressure in millibars. We use kilopascals, which are neither metric nor imperial. When asked our height and weight, most of us still say 6' and 175lbs. Ask any woman how much weight she wants to lose and it will always be 5 lbs, not 2.5 kilos.

In short, I don't believe we really converted at all. Maybe in another generation, it will happen, but it won't be in my life time.

[Ole Anderson]

Yesterday I needed to cut a groove on the bottom of a barn style sliding door. The dimensions given on the instructions, both metric and inch fractions simply didn't match what was needed for the floor mounted (finger). I suspect someone on the other side of the pond wasn't familiar with working with either system. I am a inches kind of guy, but I do find myself using the metric side of my 6" ruler on occasion for transferring small dimensions. I don't see the practicality of switching to metric after hundreds of years of records are in feet and inches, or in the case of land records, largely in feet and decimals of a foot. I get the difficulty of using fractions of less than 1/16". Watching Canadian home improvement shows, I laugh every time they refer to a 2x4 or otherwise mix the metric/imperial systems. Then there is the guy who gets xxx liters/km for "mileage". Hey a mile is 5280 feet.

[Keith Outten]

This really is about money. If you consider how many machine shops and other types of businesses own machines that were manufactured with imperial dials, gages, adjustments, etc you have just hit the nail on the head. If your buying new machines and you already have imperial machines in your shop do you really want to mix the two and accept the odds that someone on your staff will make a mistake that could put you out of business. Your staff is already comfortable with the system they grew up with, inducing a major change can be devastating for some.

Now consider a company that has an inventory of imperial fasteners that could be a hundred million dollars more of less. Drills, taps, toolboxes full of very expensive wrenches, micrometers, calipers, etc. Many trades would be affected by changing a system of measurement that for all practical purposes works perfectly and has for hundreds of years.

My shop doesn't have one machine that is setup for the metric system and if I was purchasing a new machine today it would not be one that didn't support the imperial system directly, in fact I would not even consider a duel mode machine because of the risk and because I'm just to dang old and set in my ways. I have received requests from government agencies to bid on various jobs the last few years and they sent me drawings with measurements in the metric system. My response was that if they could not send me a drawing with imperial dimensions I would no bid their job. I will not take the chance of making a mistake converting one system to another, the financial risk is unacceptable and they may as well send me documents in a foreign language.

Its all about the money...

[Rod Sheridan]

Keith, it is all about the money.

That said, when the automotive industry, and many others are already metric, you're lucky to be able to afford to refuse their business.

We'll all eventually be working in metric..............Regards, Rod.

[Steve Peterson]

Fractions do suck. I have a 12" engineer ruler that spaces each inch with 10 spaces. That's a quick way around the metric problem, sort of. You would really need an inch divided into 20 spaces to get the precision you may want. (1/16" = .064" & 1 mm = .039")

I try to always buy rulers with fractions on one side and decimals on the other. It is easy to flip it over to get the scale that I want. It's easier to use the decimal side when I am comparing with the caliper, but other times fractions are easier.

[Rod Sheridan]

I use both (or either), depending on what I am doing.

In Canada, we say that we "went metric" many years ago, but in reality, we just added metric to our long in use imperial system. We by 2 x 4 lumber and space them on 16" centers. We buy 4 x 8 sheets of plywood. But, we buy gas in litres and cold meat in grams. We measure temperature in Celsius, but we don't measure pressure in millibars. We use kilopascals, which are neither metric nor imperial. When asked our height and weight, most of us still say 6' and 175lbs. Ask any woman how much weight she wants to lose and it will always be 5 lbs, not 2.5 kilos.

In short, I don't believe we really converted at all. Maybe in another generation, it will happen, but it won't be in my life time.

Grant, isn't the Pascal the unit of pressure in the SI system? ( One Newton per square metre).

My children have absolutely no idea what units in the Imperial system are, they were born in the 80's and we were metric by then. My drivers license gives my height in cm and my medical records are metric. My van has a fuel consumption rating in litres per 100 Km, as does my motorcycle.

You're correct that the younger generation will be metric, it's you and I who use both systems.

My oldest daughter borrowed my BMW bike one day and remarked that her speed was 40 in a school zone and she was passing everyone. She hadn't a clue that the speedometer was in miles per hour :D

regards, Rod.

[Stew Hagerty]

I get a laugh every time I hear "should I switch to metric". Not about the person saying it or even whether it's a good thing to do or not. I was in High School during the mid 70's and at that time we were taught the metric system because "the Untited States was going to switching over to the metric system very soon."

Yeah, that happened.... LOL

[Ted Derryberry]

I get a laugh every time I hear "should I switch to metric". Not about the person saying it or even whether it's a good thing to do or not. I was in High School during the mid 70's and at that time we were taught the metric system because "the Untited States was going to switching over to the metric system very soon."

Yeah, that happened.... LOL

I was only in grade school, but remember that. They made a half-hearted attempt to teach us metric units. After school I went to my parents lumberyard until closing time and weighed out nails by the pound, shook gallon and quart paint cans, and loaded 2x4s for customers.

I'm certain we won't "all eventually be working in metric". Many of us won't live that long. I know I won't.

[Doug Garson]

I use both (or either), depending on what I am doing.

In Canada, we say that we "went metric" many years ago, but in reality, we just added metric to our long in use imperial system. When asked our height and weight, most of us still say 6' and 175lbs.

Actually most of us used to say 6' and 175 lbs, now we have to admit we are actually 5' 11" and 200 lbs. :cool: and who out there has the nerve to ask a women anything about her weight? :D

[Ted Derryberry]

Here's what happens when you order breakfast with the metric system. :D

https://www.cnn.com/2018/02/08/sport/norwegian-olympic-team-eggs-order-trnd/index.html

[Doug Garson]

Then there is the guy who gets xxx liters/km for "mileage". Hey a mile is 5280 feet.
Yeah, somehow kilometerage doesn't roll off the tongue as easily as mileage, I guess we should be saying fuel consumption but again mileage seems easier. Actually the measurement is xx litres/100km. Anyone using xxx litres/km would have to be driving a tank. (100 liters/km = .0235 mpg).

[Rod Sheridan]

Here's what happens when you order breakfast with the metric system. :D

https://www.cnn.com/2018/02/08/sport/norwegian-olympic-team-eggs-order-trnd/index.html

that was funny...................Nothing to do with metric however it sure was a good one.

I had the same thing happen at work, ordered 12 lengths of cable tray, supplier shipped 12 bundles............Rod.

[Ted Reischl]

I agree with Patrick about the hardest thing being visualizing just how big the measurements are. Of course if one grows up thinking in metric then it is no problem at all. My problem is that everytime someone says 50mm, I think, oh, that is about 2 inches.

It seems to me that there is too big of a gap in units. We go from a millimeter to a meter. That is 1000 times larger than the smallest unit. Yes, I know about cm, but how often do we actually see those used?

The real problem though is money. Like most people I have a shop full of tools based upon the imperial system. I am not going to just fork over all those bucks to do a conversion.

Oh, one other gripe. Wrench sizes. I need a 17mm wrench like I need a hole in the head. As I look at my wrenches hanging on the wall, how come it takes quite a few more wrenches to cover the same basic size range? Not only that, I can look at a nut and pretty much see that it is a 3/8, not a 5/16 nor a 7/16. Why? because they are about 1.6mm different in size. Of course in metric, that difference is only 1mm. Much more difficult to suss out at a glance.

Then we end up with when things need to be a wee bit larger or smaller, like for clearances. There we go, we now have measurements like 22.13 mm to get about .005 in of clearance. I guess I will have to start thinking, oh, clearance? Ok, that is a wee bit more than a mm.

Then there is the really, really big gripe! All those little lines with no small markers to define divisions. Those lines are about 30% closer than 1/16th divisions. Harder to see and work with.

I think metric is a good idea, and since it is based on a purely arbitrary standard I think those scientists could have picked something that worked for small measurements as well as big honking ones.

Here is a funny. Watch some of the old Star Treks. They are constantly talking about tracking some vessel that is 500,000km away and shooting at it. Clearly those film folks did NOT have a grip on just how far 500,000 km really is.

BTW, when I was in 8th grade almost 60 years ago they were telling us that we would be converted completely to metric within a decade or so. Shows you what they knew, huh?

[Rod Sheridan]

I agree with Patrick about the hardest thing being visualizing just how big the measurements are. Of course if one grows up thinking in metric then it is no problem at all. My problem is that everytime someone says 50mm, I think, oh, that is about 2 inches.

It seems to me that there is too big of a gap in units. We go from a millimeter to a meter. That is 1000 times larger than the smallest unit. Yes, I know about cm, but how often do we actually see those used?

The real problem though is money. Like most people I have a shop full of tools based upon the imperial system. I am not going to just fork over all those bucks to do a conversion.

Oh, one other gripe. Wrench sizes. I need a 17mm wrench like I need a hole in the head. As I look at my wrenches hanging on the wall, how come it takes quite a few more wrenches to cover the same basic size range? Not only that, I can look at a nut and pretty much see that it is a 3/8, not a 5/16 nor a 7/16. Why? because they are about 1.6mm different in size. Of course in metric, that difference is only 1mm. Much more difficult to suss out at a glance.

Then we end up with when things need to be a wee bit larger or smaller, like for clearances. There we go, we now have measurements like 22.13 mm to get about .005 in of clearance. I guess I will have to start thinking, oh, clearance? Ok, that is a wee bit more than a mm.

Then there is the really, really big gripe! All those little lines with no small markers to define divisions. Those lines are about 30% closer than 1/16th divisions. Harder to see and work with.

I think metric is a good idea, and since it is based on a purely arbitrary standard I think those scientists could have picked something that worked for small measurements as well as big honking ones.

Here is a funny. Watch some of the old Star Treks. They are constantly talking about tracking some vessel that is 500,000km away and shooting at it. Clearly those film folks did NOT have a grip on just how far 500,000 km really is.

BTW, when I was in 8th grade almost 60 years ago they were telling us that we would be converted completely to metric within a decade or so. Shows you what they knew, huh?
Hi Ted, your problem with the metric system is that you haven't put the same effort into learning it than you did with the Imperial system. I'm not criticizing you, it's just that people over estimate how much they understand either system. Most people wouldn't know what the Imperial unit of mass is, and most people won't know what the metric unit of weight is, doesn't mean we don't function in those systems in some sort of manner.

You want 0.005" clearance, did you notice that you picked a nice round number? You didn't pick 0.0043" because you wanted something simple.

In metric you would pick 0.1mm since it's simple, not 0.13mm.

Most of the things you like about the Imperial system are completely arbitrary, we use 3/4" thick material because it's more convenient than 49/64", likewise in metric we would pick 20mm rather than 19.35mm.

As to 1mm being too small, I normally use fractions down to 1/64" (standard markings on a square or 4R rule), so using mm or 0.5mm seems very familiar.

When making a 3/4" thick piece of wood you might add 1/32" or 1/64" to allow for sanding, in metric you would add 0.5mm sanding allowance.

It's all the same, you put a lot of effort into learning a system, the other system is just as good, in fact better in some cases........regards, Rod.

[Al Launier]

I considered that quite a few years ago like ~ 30-40, when the metric mania tried to take over, but couldn't justify the transition. Having a Machinist, Tool & Die Maker and Mfg. Engineering background I had memorized the decimal equivalent of fractions, dealt with decimals to 3-4 places, and also found/find myself multiplying the number of mm by 0.03937 to get the decimal equivalent. It just never worked for me.

Unfortunately, I can't shake this and still end up working to finer tolerances than is really required for woodworking. Oh well.

[andrew whicker]

I think as far as woodworking is concerned, we can all agree either one works fine.

But as far as engineering, science, etc when you have to make calculations like force, torque, power, etc. you find out pretty quickly that metric is the gold standard. 1000 grams = 1 kg or 16 oz = 1 lbm. Oh, and what is a lbm vs lbf. Oh, and everyone just abbreviates it lb. Nice. That makes things easier.

[Ted Reischl]

Rod, one of my points is that the Metric system is also completely arbitrary. The meter (m) is defined as the length of the path traveled by the light in vacuum during a time interval of 1/299,792,458 of a second. That divisor cannot get much more arbitrary. Of course any measurement system is arbitrary.

I have worked in both systems for longer than I can remember. For woodworking I find that the imperial system seems to make more sense. For other disciplines, like astronomy, not so much.

[Doug Garson]

I would suggest that those who prefer the imperial system do so because they grew up with it and work in an environment where the imperial system is the norm. The metric system seems foreign to them even though it is a more logical system (even if the base unit is arbitrary). I would include myself in that category. I'd like to hear from anyone who grew up with the imperial system and moved to and work in a country where the metric system is used, say 10 or more years ago. Which system do you prefer? Alternately anyone who has done the reverse? If you grew up with the metric system how are you finding the imperial system? Note I would not include anyone moving to/from the US and Canada as we are not a pure metric country but more of a hybrid.

[Howard Rosenberg]

Interesting question.

Officially, we've been metric here in Canada since the mid-70's.

I'm only speaking for myself but I'm a tiny hybrid.

In other words, I think in metric everything except for the length of objects. The length of a table or a bookcase etc? Imperial. Distance, temp, weight, volume - all metric.

When I'm mapping out projects, the only place I use metric is to measure up to about 10 milimetres (a centimetre.) Anything longer confuses me! But up to 10 mm is way more precise than fractions.

If you think you're interested in investigating the metric system for calculations, I'd recommend downloading a fractional calculator app for your phone. It's for use with the Imperial system but it's a lot more accurate than doing the arithmetic by hand. And no room for Imperial-to-metric conversion error.

Howard

[Keith Outten]

Keith, it is all about the money.

That said, when the automotive industry, and many others are already metric, you're lucky to be able to afford to refuse their business.

We'll all eventually be working in metric..............Regards, Rod.


Rod,

I'm 66 years old and we were told that we were going to convert to the metric system in Junior High School so we had classes to prep for the change. I expect it will take at least two more generations before fractions cease to exist.

[Jerome Stanek]

T
My shop doesn't have one machine that is setup for the metric system and if I was purchasing a new machine today it would not be one that didn't support the imperial system directly, in fact I would not even consider a duel mode machine because of the risk and because I'm just to dang old and set in my ways. I have received requests from government agencies to bid on various jobs the last few years and they sent me drawings with measurements in the metric system. My response was that if they could not send me a drawing with imperial dimensions I would no bid their job. I will not take the chance of making a mistake converting one system to another, the financial risk is unacceptable and they may as well send me documents in a foreign language.

Its all about the money...

Keith your shop has a CNC and Laser and both will switch to either so yes you do have a duel mode machine

[glenn bradley]

Wow, this one really got a lot of traction :). They taught us metric and threatened full conversion a couple of times in school, even changed all the speed limit signs out here once in a typical great use of tax dollars. I can use either but, prefer imperial. Certainly this is partially due to being primarily raised on it.

The result of a few false starts during my lifetime is that I am comfortable estimating volumes and short distances in either. My estimation of metric speed is pretty useless but, 'about' 25 mm to the inch works visually and we all know 'about' the length of a 100 mm cigarette. My 35 years of octal, decimal and hex at work has done something to my brain. I find it almost like a serotonin spike when thinking in imperial. Thinking in fractions soothes my mind when I am in the shop. It is certainly nothing to go all Ford/Chevy or Tastes-Great/Less-Filling over :).

[Ted Derryberry]

9mm or .45 ACP?

[Grant Wilkinson]

Rod: You are correct. I should have said that in Canada, we seem to be the only "metric" country using pascals or really kilopascals for pressure - other than France. Elsewhere, millibars and bars are used.

I'm 68, so grew up with Imperial, but many of the cars that I worked on growing up were european, so metric wrenches have been in my kit for a very long time. Renaults, VWs, Morgans, MGB's etc, were always metric as far as I know. I must admit, too, that driving at 120kph seems so much faster than driving 75mph - a neat mind game. Also, it makes it easy to figure how how much longer I'll be on the road. Take the "mileage" on the road sign and divide by 2 and I instantly get the number of minutes I'll be driving.

Doug: You have me there. :-)

[Keith Weber]

9mm or .45 ACP?

Definitely .45 ACP -- You want to stop it, not poke holes in it! :)

[Steve Demuth]

Then there is the really, really big gripe! All those little lines with no small markers to define divisions. Those lines are about 30% closer than 1/16th divisions. Harder to see and work with.

This is the one substantive problem I have with Metric in the woodshop. I can mark and cut to 16ths of an inch very easily. I just can't do it with tenths of a mm - measure, yes, mark, no. I'm sure that's a skill all the millions of people who work wood in metric have acquired, but it's pretty clear that in my 7th decade, I will never be a natural with .1 mm increments.

[Steve Demuth]

My 35 years of octal, decimal and hex at work has done something to my brain. I find it almost like a serotonin spike when thinking in imperial.

Yes! I find binary factions entirely natural. But I also find decimal fractions entirely natural. I use both inches with binary fractions and metric with decimal, often on the same project. Then I switch to metal machines, and use inches with decimal fractions. Really it's no different than being equally comfortable with typescript, Java, C++ and assembler. Use the metaphor / measurement that solves the problem.

Until you have to work with others. Then agreement on the language matters. Which is why, ultimately, the US should be metric. Sooner is better.

[Malcolm McLeod]

... 35 years of octal, decimal and hex at work has done something to my brain. ...

Metric and imperial are for sissies!:rolleyes: I do everything in my shop in biquinary.:cool: (go ahead, find such a Stanley tape ...I dare ya.:confused:)

Don't believe me? Well OK, but I thought about it once!

[Halgeir Wold]

Hi guys.... It's all about what we are used to,- it's that simple. I grew up with metric, but in my work I have used also used imperial for decades, and the conversion is actually quite simple once you get used to that too. Some here say "It's too difficult with only meters and millimeters" - in common day speech most europeans use meters and centimeters- millimeters are for construction and precision work, - and tenths or thousands of millmeters, of course. I am an electronics engineer, and when designing cicuit boards, I use tenths and hundreds of inches, as that is the most common pitch for component sizes - it's really all about habits....
Some here say that "metric is just a set of arbitrary measures", - both false and true. The SI system was devised for making a common set of measures for scientific and everyday use, and to get rid of the problems with measures being different between countries and even regions within a country. Old measurements was a source of a lot of confusion and even downright scams and fraud. The meter was originally defined as being one ten millionth part of the distance from equator to the north pole, as calculated and measured by surveyors from the french science academy, - and twelve official platinum prototypes were made, and public copies were installed at several places throughout Paris, for people to observe. The wavelength of light or distance of light travelled stuff, is the modern method for exact reproduction of the unit.
Imperial measures is as you know not an US invention, rather an inheritance from the British Empire, with measures that actually are more arbitrary the the scientifically based metric system, - even if some of the SI units appear to be arbitrarly defined, a lot of the imperial units actually dates back to rather poorly defined roman measures......
"A mile is the distance of a thousand paces" someone wrote.... I'd like to see the man who spans 1.609 meters in one pace.... :) and where is the logic and fractions in a mile which is actully 5280 feet, or 1760 yards - or even 63 360 inches... ;)
No offence - I find these metric vs imperial discussions quite amusing, and I often pull the legs of british and US collegues on this matter.... :D

[Rod Sheridan]

Rod,

I'm 66 years old and we were told that we were going to convert to the metric system in Junior High School so we had classes to prep for the change. I expect it will take at least two more generations before fractions cease to exist.

You're probably correct Keith, it does seem to be a very slow process in North America for some reason....Rod

[Keith Outten]

Jerome, your right about my laser engraver and CNC router both are capable of either imperial or the metric system. However they are simple software configurations so there's no reason to be concerned with making a mistake. Even if I load a metric drawing the software automatically converts it to imperial dimensions, but that's unlikely to happen since I don't accept metric projects. I am fortunate that I am in a position to be able to bid or no-bid projects that don't fit my requirements. Currently I am basically semi-retired so I have even more flexibility concerning my shop schedule.

I can't remember any of the details but many years ago NASA had an incident where a metric dimension was misinterpreted as imperial and the lander missed a planet by a hundred miles. They were embarrassed about the incident but it was just taxpayers money so no big deal. If that happened to me in my little shop it would be devastating.

I spent half my life as a Quality Control Inspector and I have had my share of situations where a machine shop I was at to inspect a project before they could ship and found dimensional errors or even drawings that were not the current revisions. I've seen shop supervisors faces turn white as a ghost when I explained a problem I found and they instantly knew that they were in big financial trouble. I learned early in life how serious errors can be and when I opened my own shop I made certain decisions about basic policies I had to abide by to limit my own liability. Inspectors make a living based on the fact that people make mistakes, we had T-Shirts at North Anna Power Station in the late 70's that said "We Live By Your Mistakes". Sometimes they were billion dollar mistakes that made it crystal clear to the customer that inspection was worth every penny invested :)

There's nothing simple about any system of measurement, its more like a science than it is a directive in a specification. For instance there is a right way and a wrong way to use a simple micrometer, if you want to learn the right way find a Master Machinist and ask him to teach you how its done properly.

It really is about the money folks :)
.

[Mark Wooden]

Hmmmm....
I started to read all the replies here and lost interest in the debate and decided to post my opinion, which, with $2, will get you a medium cup of coffee.....
I tend to side with Martin Wasner, doesn't matter what the system is, the physical universe rules in measurements. Worked with a guy once who used actual sticks marked out on site for measurements, rarely used a rule. Very accurate.

But, in answer to the OP-
Start with Metric , Finish with Metric. Same for Imperial. Don't do conversions, waste of time. Don't use combo rules either- too easy to get confused and make a mistake. If I have to use a lot of components that are metric sized, I'll tend to do the entire job in metric and I put the imperial rules and tapes away.
Use whatever system is easiest for you, but my advice is to not mix them. YMMV

[Jim Becker]

Start with Metric , Finish with Metric. Same for Imperial. Don't do conversions, waste of time.

Sage words....

[Curt Harms]

Strange as it sounds, I think the hardest part of switching from imperial to metric is visualizing the measurements. Imperial is native- it’s like thinking in English.

Not to a young person growing up in a country that has been metric for longer than they've been alive.

[Rob Luter]

Decimal inch for me. I think in three place decimals.

[Brian Holcombe]

I have metric, shaku and imperial tools and if one fixates to much on the dimensional size of them, it will drive you crazy. Another added to the group recently since I have a slot mortiser and the good bits are in metric, 6mm is damned close to 1/4"....but not exactly. It's off by 14 thousands, thats enough to make a pretty unsightly gap in a setup. I counter this by always setting my marking gauges to the tool, not to the measurement.

I've grown accustomed to doing this for Japanese tools which are sold in metric but they're made in Shaku (traditional Japanese measurement system). Shaku is very close to inches, so they end up measuring almost imperial and almost metric.

My friend Jim, a wonderfully talented teahouse carpenter, described Shaku as being just close enough to screw up your work. One Shaku is 11.93", almost enough to ignore but not quite. One Bu is .1193", very close to 1/8" and two Bu is .238", right there between 1/4" and 6mm.

So rather than drive myself nuts, I simply set my gauges or tool setting exactly to the work or the tool bit, never to the measurement.

[Dave Zellers]

So rather than drive myself nuts, I simply set my gauges or tool setting exactly to the work or the tool bit, never to the measurement.

Great tip.
Rather similar to cabinet makers who don't use tape measures but rather transfer measurements with a story stick.

[Dan Schmidt]

For my type of woodworking projects, 1/16" never felt accurate enough. 1/32" was overkill and harder to read/assess. I found 1mm (which is in between) to be perfect. All of my equipment and scales are set up for dual measurement scales, but I find myself only using metric. Took a bit of getting used to but now I would never go back.

Dan

[Phillip Gregory]

I use imperial measurements as tooling, stock, and most woodworking fasteners widely and easily available in the US are imperial. The only metric in my shop is fasteners on the newer equipment.




I've run into all kinds of stuff in construction that's "metric" but when you convert you find that it's based on an imperial standard. Not just construction either. If you know anything about firearms you've heard of the AK47 round which is 7.62x39. That's a bullet diameter of 7.62 mm. Guess what that converts to. 0.300", which is "30 caliber".

The 7.62x39 uses the 0.311" bullet from the .303 British. It uses (or should use) a different bullet than the American 7.62x54 which despite being a "7.62 mm" round uses 0.308" bullets. Shooting a 7.62x39 round loaded with a .308 dia bullet through an AK leads to poorer than normal accuracy, shooting a 7.62x54 round loaded with a .311 dia 7.62x39 bullet may blow up the rifle.


9mm or .45 ACP?

A .45 ACP bullet is close to 12 mm in diameter, a 9 mm bullet is just a fuzz smaller than a .38/.357 so they are quite a bit different in size. Personally, I'd prefer neither. Both of those are rimless cartridges that headspace on the case mouth. Give me a rimmed cartridge any day, way easier to reload and easier to shoot in a revolver or pistol caliber lever gun. I'm not a big fan of semi-autos.

[Ted Derryberry]

I wasn't implying that the bullets were actually the same. Anybody that knows anything about firearms knows that few cartridges or bullets are the actual size of their designation. Similar to "2x4s". My point is that common metric cartridges, like many "metric" standards in other industries, are often based on imperial units.

7.62mm does in fact convert to exactly 0.300".

[William Adams]

For what it's worth, my understanding is that 38 special isn't taken from a decimal designation, but rather a corruption of the 3/8" drill which was used to enlarge the cylinder of a cap and ball revolver when converting it from black powder, which is why the actual bullet dimension is .357.

[Phillip Gregory]

For what it's worth, my understanding is that 38 special isn't taken from a decimal designation, but rather a corruption of the 3/8" drill which was used to enlarge the cylinder of a cap and ball revolver when converting it from black powder, which is why the actual bullet dimension is .357.

The designation came from the earliest days of metallic cartridges when all metallic cartridges were rimfire with heeled bullets the same diameter as the case, like the .22 Long Rifle. The .38 Special's case diameter is 0.379" which is essentially identical to the old .38 caliber rimfire rounds which actually did use about an 0.38" diameter bullet. The .38 Special being a more modern centerfire cartridge uses non-heeled bullets that have to fit inside the case mouth and thus must be smaller in diameter.

[johnny means]

...but my advice is to not mix them. YMMV

So true. i was having a conversation at work about making a part. Coworker didn't seem to be catching my drift no matter how many times i ran through it. finally, he looks at me and asks,"Are you talking standard or metric?" It took me a second to realize that I'd been switching back and forth for an entire ten minute conversation about measurements. I'm not some sort of conversion savant, but i do tend to see most specs in standard, while hardware mounting comes to me in metric.

[Jim Becker]

Not mixing is a good idea...human nature can be dangerous in that situation. Related to that, I started a new project yesterday which had been planned for some time and was originally sketched out and cut-listed in inches. It didn't take long for it to drive me nuts because I've thoroughly been enjoying working in metric for a few months now...so much so, that I left the shop, remeasured the job (this one is for my house so I didn't have to go far :) ), hit the computer to update the cut-list and then went out and cut out everything. Even when I was doing the "figuring" for a planned mini-split, the tape with inches didn't last long and I just switched out to the metric tape since the diagrams had both measurements. I guess my mind has gone far enough in that direction that it's now compelling...but I'm weird like that. :D

[Chris Parks]

You just validated my comment on the US changing by degrees or erosion of imperial as people and industry work out that it is a better system overall.

[Jim Becker]

Chris, a lot of industry is already there. It's use "mere mortals" that are left. Change is hard, but my experience is that once I choose to use the system seriously, its REALLY hard to go back. But that's me...

[Brian W Evans]

I side with those who see the metric system as better - it just makes sense. That said, I work in imperial measurements since I grew up in the U.S. and most domestic woodworking materials (fasteners, lumber, etc.) is imperial.

One thing I've noticed as a result of using imperial measurements is that I tend to use measurements that avoid fractions - not always, but often enough. I was making a drawing yesterday where everything was in 16ths of an inch. I was spending a lot of time adding and subtracting fractions when, as I was just about finished, I realized that almost everything I had done was 1/16" shy of a full, 1/2, or 3/8 inch. Since I was just developing the idea and knew I was going to be changing a lot of things, I added that 16th to make the numbers easier to work with. Sure enough, my revisions went much faster.

I wonder if I would have done the same with something that was, say, 49mm and rounding to 50mm? I don't think I would. It really made me think about the design implications of my preference (am I alone in this?) for round numbers vs fractions, or at least bigger fractions, and whether by doing so I was abandoning a better design in favor of easier math. Those classical proportions are pretty precise and don't look quite right if they're off even a little bit.

Of course, maybe this is just the comeupance my math teachers always promised me. :p

[William Adams]

I like nice even numbers, and that's why I prefer Imperial --- if need be, I can grab a DTP ruler and get 72 points per inch, and I'm fine at estimating a half-way or one-third/two-third position between them if need be. Maybe I'd be happy if I could find a good quality ruler which had half and quarter and third millimeter divisions on it. Problem is, the ruler I'd really like to replace is a 4-fold brass bound one and the only replacement I can find is ~$400.

Anyone know of a good source of scaled and folding rulers for metric work?

[Ted Derryberry]

What puzzles me is why many of those who use metric spend so much effort trying to convince others that its better than imperial and that they should switch to metric. Why would they care what other people use? If I'm happy using imperial then what difference does it make to them? Could they be subconsciously trying to convince themselves? On the other hand, you seldom see people who use imperial trying to convince metric users to switch. Maybe its rooted in the culture, admittedly dying, of the US that has historically said, "go your own way and I'll go mine", vs. the European tendency to micromanage society.

As for the micromanaging socialists on this thread, you can take my imperial ruler when you pry it from my cold dead hand.

[Rod Sheridan]

I side with those who see the metric system as better - it just makes sense. That said, I work in imperial measurements since I grew up in the U.S. and most domestic woodworking materials (fasteners, lumber, etc.) is imperial.

One thing I've noticed as a result of using imperial measurements is that I tend to use measurements that avoid fractions - not always, but often enough. I was making a drawing yesterday where everything was in 16ths of an inch. I was spending a lot of time adding and subtracting fractions when, as I was just about finished, I realized that almost everything I had done was 1/16" shy of a full, 1/2, or 3/8 inch. Since I was just developing the idea and knew I was going to be changing a lot of things, I added that 16th to make the numbers easier to work with. Sure enough, my revisions went much faster.

I wonder if I would have done the same with something that was, say, 49mm and rounding to 50mm? I don't think I would. It really made me think about the design implications of my preference (am I alone in this?) for round numbers vs fractions, or at least bigger fractions, and whether by doing so I was abandoning a better design in favor of easier math. Those classical proportions are pretty precise and don't look quite right if they're off even a little bit.

Of course, maybe this is just the comeupance my math teachers always promised me. :p

Brian, that's exactly what I do when designing furniture, I make pieces 20mm thick, or 30mm, or 50mm for legs........regards, Rod.

[Chris Parks]

What puzzles me is why many of those who use metric spend so much effort trying to convince others that its better than imperial and that they should switch to metric. Why would they care what other people use? If I'm happy using imperial then what difference does it make to them? Could they be subconsciously trying to convince themselves? On the other hand, you seldom see people who use imperial trying to convince metric users to switch. Maybe its rooted in the culture, admittedly dying, of the US that has historically said, "go your own way and I'll go mine", vs. the European tendency to micromanage society.

As for the micromanaging socialists on this thread, you can take my imperial ruler when you pry it from my cold dead hand.

You do not know my politics and why the reference to politics? I could assume your political leaning from that statement but I won't as I might be wrong.