Worst measuring tools?

[Tom Walz]

Worst measuring tools?

I'm working on a presentation on measuring and discussing things like precision, accuracy, repeatability, resolution and so on.

I'm also going to start by talking about the fact that not all measuring tools are accurate or equally accurate.

I would like to find some really inaccurate tools for the demonstration.

If anyone had any they would like to sell I'd be happy to buy them or trade new tools for them.

Thank you,
Tom Walz

[Richard Ray]

Worst measuring tools?

I'm working on a presentation on measuring and discussing things like precision, accuracy, repeatability, resolution and so on.

I'm also going to start by talking about the fact that not all measuring tools are accurate or equally accurate.

I would like to find some really inaccurate tools for the demonstration.

If anyone had any they would like to sell I'd be happy to buy them or trade new tools for them.

Thank you,
Tom Walz

Like my Ronco Rolling Ruler?

[Peter Kelly]

Can't go wrong with any of these gems: http://www.harborfreight.com/hand-tools/calipers-dial-indicators-micrometers.html

[David Giles]

Like this Starrett ruler? Some folks were incredulous that a Starrett product could be less than accurate. So was I until this ruler arrived. But return shipping is more than it is worth and it still makes a good straight edge. The middle ruler is from Rockler. Nicely engraved markings and dead on accurate based on the Incra fence system. Bottom ruler is an old, dropped, beat up Johnson that still works sufficiently well for most tasks. Fastcap and Stanley tapes are sufficiently close for carpentry.
http://i29.photobucket.com/albums/c290/davidgiles/ruler1.jpg

http://i29.photobucket.com/albums/c290/davidgiles/ruler2.jpg

[Matt Meiser]

This is kind of funny, but actually serious. I don't know your audience, but:

Stepping off with your feet. Have three people measure the room across and back. Bet you get 6 different answers. Be sure to pick a big guy and small woman. Then pick another person who has the same size feet as one of the others.

Using your fingers as calipers. "Its about this big" I bet most people couldn't pick the the block sitting on one table from a few similar sized examples that matches a reference block sitting on another table across the room

Weighing using your hand. Be sure to move it up and down--that improves the accuracy :rolleyes:

You can keep your tools thought--I want to keep my hands and feet. :D

[Jeff Duncan]

The problem to me is you have to define desired accuracy and then pick a measuring tool to do the job. The cheapest HF tape measure should be plenty accurate enough to frame a house. I doubt you would see an engineer at NASA measuring a part in the metal lathe with it though.

The point being that of course all tools are not equally accurate, but that doesn't mean that a less accurate tool is inaccurate for it's intended purpose.

Then of course you could get into where a lot of the inaccuracy comes from.....the person doing the measuring!

anyway, just my random thoughts....good luck,
JeffD

[Jeffrey Makiel]

May be the Starret ruler is calibrated as an outdoor ruler when it is very, very cold. :)
Jeff :)

[george wilson]

I think gov't. spec. accuracy for a tape measure is 3/16" out per 6'. I haven't really seen one that much out,but thought it worth mentioning. I bought a 20' long tape measure from a bin in the grocery store for less than $4.00. It is right on,just fine.

[Jerrimy Snook]

George Wilsons post http://www.sawmillcreek.org/showthread.php?111491-A-batch-of-18th.C.-folding-rules-we-made was interesting about accuracy of folding rules.

Are you asking us "If you were sitting through a presentation about precision and accuracy would you use a ruler or a watch to see how long it is until break time?"

[Mats Bengtsson]

...I'm also going to start by talking about the fact that not all measuring tools are accurate or equally accurate.

I would like to find some really inaccurate tools for the demonstration.
...
Take any good ruler, or any good measuring tape. For all of them applies the same. There is a measuring done when placing it, when deciding on the mark to tick off at and when doing the tick off with a pen or knife, and when aligning a tool to the mark. Every time you measure, this contributes to give a different result. Measuring is inaccurate.

The alternative is not measuring better, rather it is not to measure.

If you do 5 shelves in a book case with the measuring method, you get 5 different lengths. Some of them might be close. If you instead set up the table saw once, and make 5 cuts without remeasuring, the difference in length will be very little. Repetition beats measuring.

Measuring compared to repetition is about as good as comparing a one meter ruler used to measure a meter, with a 25 centimeter ruler used for doing the same measuring.

--- Mats ---

[Walter Plummer]

In defense of the L.S. Starrett Co., the aluminum yardstick with Starrett's name on it is just an aluminum yardstick. Starrett has a line of contractor/homeowner grade tools. I believe they purchased another company and just put their name on them. These tools have nothing to do with their line of precision measuring tools costing many times what that yardstick cost. A 1 1/4" x 36" rigid steel rule with 4r easy read graduations(1/8" 1/16" 1/32" 1/64") cost $156.00. Aluminum yardstick $15.00.

[Bruce Wrenn]

Measure it with a micrometer, mark it with a piece of chalk, and then cut it with an axe. Precision work, measured to the thousandth!

[Steve Griffin]

An example that comes to mind is the magnifying bubble cursor which comes with some table saw and miter saw stops. You know, the kind that reads totally different depending on the angle you view it?

My shop fox fence on my grizzly saw came with one, and I got it out of my shop as soon as possible.

http://www.sawmillcreek.org/showthread.php?97703-Thankful-for-new-G1023-TS-but-cursing-the-curser.

Another example is too close of increments. I've never once used the 1/64 side on my starret combo square as it looks like solid grey to my eyes. I can interpolate pretty close to 1/64 with the 1/16 side though.

[Roy Turbett]

You could demonstrate how "pencil creep" happens when you use each successive piece you cut as a pattern for the next. Or demonstrate the "rule of thumb" that has its origins in English common law that limits the size of the stick you can use to beat wife to one that is no thicker than your thumb.

As for tools, the most inaccurate tool I came across is a laser on an older 12" Bosch sliding miter saw. The line moved close to 1/16" as I lowered the blade to make my cut. The new "Glide" version of the saw solved the problem by eliminating the laser!

[Chris Mahmood]

In defense of the L.S. Starrett Co., the aluminum yardstick with Starrett's name on it is just an aluminum yardstick.

How is Starrett pimping their good name in order to fool consumers into thinking they are buying something they aren't a defense?

[Chris Mahmood]

Or demonstrate the "rule of thumb" that has its origins in English common law that limits the size of the stick you can use to beat wife to one that is no thicker than your thumb.

http://www.straightdope.com/columns/read/2550/does-rule-of-thumb-refer-to-an-old-law-permitting-wife-beating
http://en.wikipedia.org/wiki/Rule_of_thumb#Origin_of_the_phrase

[Walter Plummer]

How is Starrett pimping their good name in order to fool consumers into thinking they are buying something they aren't a defense?
I don't think they are trying to fool anyone. They are trying to compete in the everyday tool market against General, Empire , etc.

[Alan Lightstone]

I have that sonic ruler thing on my iPhone. Wanna buy my old iPhone? ;)

[William Addison]

In an earlier post in this thread someone implied that HF tools are inaccurate, my experience with their digital calipers and micrometers is the opposite. I have some Starret instruments but I don't like to keep them on the workbench because they'e so expensive. I do compare the HF to them on occasion, and I've never been so much as a thousandth off. The downside is that the HF stuff does wear out.

[Dan Hintz]

Weighing using your hand. Be sure to move it up and down--that improves the accuracy :rolleyes:
You laugh, but there's actually some accuracy in that statement. ;)

It works on the same principle as our eyes naturally shifting back and forth ever so slightly to prevent "burn-in" of the cones/rods. Stare at a black spot on a white page for a minute, then stare at a blank page and see a ghost of the black dot in your vision... that's what the shifting helps avoid. Pick pockets can lift your wallet so easily because after a while, your body gets used to the wallet pressing up against it... doesn't take long, just a few minutes. As you lift and drop the weight in your hand, it ever so slightly changes the pressure, giving your body a chance to notice the difference.

[Keith Outten]

Technically speaking a ruler is a monarch, a measuring device is a scale.

Tom, I may have some study material from my days as an Inspector that might be of help. I use to teach visual inspection and was a Level III NDT Examiner for a company at NASA Langley. There are some very good books on the subject that are available from The American Welding Society and The American Society of Nondestructive Testing. I know that I still have an AWS Certified Welding Inspector Training Guide in my desk at work that may have some information you could use. I may also still have some of the tests that I use to use to certify Inspectors back in the day.

I have a 6" plastic caliper in my toolbox at CNU that you can have, it is so bad it isn't useful for any type of measurement.

My reference material is a bit old but the science of measurement hasn't changed much lately.
.

[Zach Callum]

Go to the local big box, take a few tape measures from the rack, and test them. Chances are that you will find at least a couple that do not line up. I have a couple that are off by about 1/32. It also seems like the newer tapes have fatter lines.

Keith, I would be interested in seeing the tests that you referenced, it just seems interesting to me.

[Keith Outten]

I will look for the tests this weekend. I know they are stored in my storage building in a box so they should be easy to find.
.

[Jim Matthews]

If the same instrument is used for all measurements on a project, errors are constant.

Precision is relevant in so much as the user can detect errors.
(Stuffing business cards in gaps, for example.)

If the measuring device is crude, but the observer keen, precision can be built in.
209287

[Myk Rian]

Worst measuring tools?

I would like to find some really inaccurate tools for the demonstration.

Something I'm sure we have all used at one time, a length of string.
Measuring, creating circles, etc. Not very accurate due to stretching.

[Myk Rian]

In an earlier post in this thread someone implied that HF tools are inaccurate, my experience with their digital calipers and micrometers is the opposite. I have some Starret instruments but I don't like to keep them on the workbench because they'e so expensive. I do compare the HF to them on occasion, and I've never been so much as a thousandth off. The downside is that the HF stuff does wear out.
I took the post as HF having pretty good tools, as they were called "gems".
True, you have to be careful with what you buy there.

[Neil Brooks]

It may be worth discussing the difference between precision/accuracy and ... consistency.

It's like a bathroom scale. It may not be *right,* but ... if it's consistent ... that's probably good enough.

I stick with the same tape measure for an entire project. I have no idea how "accurate" it is, but ... since it IS consistent ... my results are just fine.

The same can't really be said for things like arbor/bearing runout, how far off a TS blade, or BS table is from 90*, etc., but ... for project measuring ... I've found consistency to be the #1 thing.

Enjoy your talk !

[Jason Dreyer]

An example that comes to mind is the magnifying bubble cursor which comes with some table saw and miter saw stops. You know, the kind that reads totally different depending on the angle you view it?

My shop fox fence on my grizzly saw came with one, and I got it out of my shop as soon as possible.

http://www.sawmillcreek.org/showthread.php?97703-Thankful-for-new-G1023-TS-but-cursing-the-curser.


I have the same fence with the same bubble cursor, and it's horrible. I just snagged the Bies cursor that was linked on that thread. Thanks for the link!

[Chris Tsutsui]

The worse measuring tools are probably more due to user error.

For instance many measuring indicators will show different measurements depending on your point of view. An example is What angle is your head relative to the indicator that hovers slightly over a scale like in many table saw fence systems. If you use one eye or the other and your head isn't in the same position when viewing you could get various measurements.

I say the best measuring tools are calibrated professionally, shock proof/durable, and get rid of "user error" by perhaps being digital.

Tape measures have a few flaws such as the metal tape can get dinged or bent which throws off accuracy, also the metal grab pin on the end might get loose or stuck throwing off the measurement.

My Mitutoyo rulers are hardened thick steal with easy to read precision markings because the ruler has an almost "white" frost surface with black etchings. This is sort of my "go to" ruler.

[Tom Hargrove]

Last fall, I was working on a small construction project (framing stage) with two other volunteers. Two of us were using Stanley tape measures. The third fellow (who is an architect) was using a no-name tape measure that came from a big box store. As the day progressed, the cutting errors were really starting to add up, especially when one of us was measuring and another was doing the cutting. I collected all three tapes, and discovered that the no-name/house brand tape (which came from a store that features orange in its advertising, logo and decorating schemes) differed from the two Stanleys by almost 1/4" in six feet. The architect was taking and calling out very precise (i.e. consistent to 1/32" on each meaurement), but consistently inaccurate measurements!

When I returne home, I checked all of the Stanley tapes I have in the house (and I am embarassed to say how many I have accumulated over 30 years) and found them all to be consistent at both the six foot mark and twelve foot mark.

[pat warner]

Not what you asked for.
Just wanted to point out, the study or measurement (metrology), is, in my view, more important than the measuring tool.
Guys use story stix e.g., and build whole kitchens with them
Great measuring tools are wonderful, to be sure, but it takes me hours to show my students how to use them. And they have to practice.
They're sensitive to cleanliness, angle of view, optics, touch, iteration (how many times in a row can you get the same measurement), and how you use them. A caliper can measure thickness x subtraction (dado e.g), direct measurement in the jaws, depth gage and x secondary, or even tertiary reference systems. When your guys understand all that stuff, they're ready to blow some real money (http://patwarner.com/images/met.jpg).

[Dan Hintz]

Not what you asked for.
Just wanted to point out, the study or measurement (metrology), is, in my view, more important than the measuring tool.
Guys use story stix e.g., and build whole kitchens with them
Great measuring tools are wonderful, to be sure, but it takes me hours to show my students how to use them. And they have to practice.
Depends upon what you're doing with it. If I call you up on the phone, that story stick mark isn't going to tell you squat... but if I tell you I need a metal bar 8" long, +/- 2 mils, you had better have a quality gauge at both ends of the phone.

[Andrew Hughes]

All this talk reminds me of when my brother and i roofed together.We had a couple jobs were we marked lines on big panel roofs .Something like three hundred feet long and fourty feet high.We would fight and argue the lines would never come out straight.We finally agreed only one of us could mark the verticles or horizontal.Or a row or two of tile would vanish.Which turned out to be me since my brother was older than me.Marking lines sucked.

[Brian Kent]

My cubit is the same each time I use it.

[John Coloccia]

Grab two digital calipers. Set one to some measurement and lock it. Record the value and turn it off. Pass that caliper around with a second set. Challenge them to measure the first caliper with the second, some using the outside measurement and some using the inside. I'll bet you that quite a few end up off by at least 2 or 3 thousandths (and some will be off by more). Does no good to have the best tool in the world if you don't use it properly.

[Don Bullock]

You ned one a Tape Measures for Dumb Handymen (http://www.surplusgizmos.com/Tape-Measure-for-Dumb-Handymen_p_885.html).

209493209494

[Larry Edgerton]

The "Speed Square".

Nice idea I guess, but I have yet to see on that is true.

They are banned from my jobs......

Larry

[Greg Hines, MD]

Somewhere I saw a gag ruler make out of rubber. Maybe try that.

[Carl Beckett]

Go to the local big box, take a few tape measures from the rack, and test them. Chances are that you will find at least a couple that do not line up. I have a couple that are off by about 1/32. It also seems like the newer tapes have fatter lines.


Yep - I saw this done once and was quite surprised at the differences. It made a good demonstration/impression on me at least and something I now think of when doing a project (whether my measurement is consistent)

Also, I created a problem for myself once where I was measuring an inside distance (framing) and then cutting a stud to length using the outside mode of the tape. That particular tape measure gave a pretty big difference depending on whether you were measuring inside or outside. Swapping tapes fixed it (but not before cutting a bunch of studs short).

[Mike Cruz]

Tom, I bought a Wixey angle gauge cube thing from Woodcraft a year or so ago. One day, it just quit working. I called Woodcraft and they replaced it no questions asked. The replacement is SO off. I was looking to make a cut around 12 degrees (assuming straight up and down is 0...or 78 degrees if straight up and down is 90) and I just about ruined the piece of wood I had to cut. It was WAY off. I made 3 cuts...each time not giving my the angle I needed. I scratched my head, and scratched my head. Hit the paper with the pencil to calculate the math, used a calculator, embarrassingly asked my BROTHER to recheck my math. Finally, I used the gauge on the table saw and the cut came out perfect. I've been contemplating sending this one back too...