Question for the Imperialists

[Hilton Ralphs]

Over here in Metricland, screws are reference by their root diameter at the top x length. Pretty simple.

Any of the decent plans or even hardware sold in North America always refer to screw numbers and I've never really comes to terms with it...Until now hopefully.

I was taking a look at the Lee Valley Tap & Drill Sets and noticed that they are for sizes #2-56 up to #10-24. Do these numbers correspond to screw sizes?

I can visualise any of the bolt/tap sizes from #1/4-20 upwards because it's a definitive number based on a calculation but below that is all Greek. I always have to look up the size of say the #8-32 in decimal and then convert to Metric and then exclaim "Ah it's close to 4mm!".

I've probably even more confused now because I have no idea what a #5 or #14 screw looks like or even which tap/drill set to get to substitute the wood screw for a machine screw.

Do I just suck it up, print out a nice chart and worry about World Peace instead?

fanx.

[John Coloccia]

Do I just suck it up, print out a nice chart and worry about World Peace instead?

fanx.

Just like 1/4-20 is a 1/4" screw, 20 threads per inch, a 2-56 designation is a #2 screw, 56 threads be inch. It's a bit anachronistic, but you will generally only see 2-56, 4-40, 6-32, 8-32 and 10-32.

So yeah, just print out a chart if you need clearance hole sizes, and move on. 2-56 is a bit over 1/16", and 10-32 is close to 3/16". The other ones in between are suitably in between. :) I can't tell you why thread standards resort to this crazy numbering scheme below 1/4", but it does.

[lowell holmes]

http://www.woodmagazine.com/woodworking-tips/techniques/free-woodworking-charts/?page=4

If you open the link above, you can download a chart graphically showing woodscrew sizes.

[Pat Barry]

Over here in Metricland, screws are reference by their root diameter at the top x length. Pretty simple.

Any of the decent plans or even hardware sold in North America always refer to screw numbers and I've never really comes to terms with it...Until now hopefully.

I was taking a look at the Lee Valley Tap & Drill Sets and noticed that they are for sizes #2-56 up to #10-24. Do these numbers correspond to screw sizes?

I can visualise any of the bolt/tap sizes from #1/4-20 upwards because it's a definitive number based on a calculation but below that is all Greek. I always have to look up the size of say the #8-32 in decimal and then convert to Metric and then exclaim "Ah it's close as dammit to 4mm!".

I've probably even more confused now because I have no idea what a #5 or #14 screw looks like or even which tap/drill set to get to substitute the wood screw for a machine screw.

Do I just suck it up, print out a nice chart and worry about World Peace instead?

fanx.
Yes - a good conversion chart is the best answer. The screw numbers, kinda like gauge sizes for sheet metal or wire have no inherently understandable relationship to diameter.

[Steve Rozmiarek]

I suggest one of these if you are a visual type of person. I have several extras, PM me if you want one.

http://www.4custom.com/e/Bolt%20Gauge%20Green%20Front.jpg

[Daniel Rode]

That's a darn useful looking gauge. Where'd you find it?

I suggest one of these if you are a visual type of person. I have several extras, PM me if you want one.

http://www.4custom.com/e/Bolt%20Gauge%20Green%20Front.jpg

[Steve Rozmiarek]

That's a darn useful looking gauge. Where'd you find it?

Fastenal left me half a dozen or so over the years, they sell them. Most decent bolt stores carry them. Here is a link to the fastenal one that I prefer for less than $10:

http://www.fastenal.com/web/products/details/63151?searchMode=productSearch&filterByVendingMachine=

[Daniel Rode]

The US is a crazy mix of metric and imperial. Screws are mostly imperial. Nuts and bolts sold loose are 90% imperial. Metric sizes are readily available, but imperial is the norm. However, nuts and bolts on products might be either or sometimes both. In the US one needs a full set of both tools.

I like imperial measurements because I grew up with it and it's familiar but we'd all be better off using metric like the remainder of the world. It's too late for me, but maybe my grand-kids can be saved :)

[lowell holmes]

When you said screws, I thought of woodscrews. The chart I mentioned in an earlier post was for wood screws.

Straight threaded fasteners are commonly called nuts and bolts. a 10-32 nut and bolt would be a #10 bolt with 32 threads per inch.

They have a device we can buy now that we can screw a nut on or a bolt into that will identify the size and thread. I need one for metric bolts and will probably will buy one.

I spoke somewhat in error. I don't think I've ever seen a 10-32 bolt. A #10 bolt is commonly 24 threads per inch, thus 10-24. 6-32's are common.

[Jim Koepke]

The US is a crazy mix of metric and imperial. [snip] In the US one needs a full set of both tools.



Actually many of the sizes between metric and inch are interchangeable (the formatting got lost in the chart below via cut and paste so --- was inserted to separate the numbers):

Metric to Sae wrench sizes. 6.5mm is common in many wrench sets. A "t" next to the wrench size indicates this wrench will be tight on its equivilent size nut, i.e. a 14mm wrench is snug on a 9/16 nut.

Millimeters Inch
6 --- N/A
6.5 --- 1/4t
7 --- N/A
8 --- 5/16
9 --- 11/32t
10 --- N/A
11t --- 7/16
12 --- N/A
13 --- 1/2t
14t --- 9/16
15 --- 19/32 (not common)
16 --- 5/8
17 --- N/A
18 --- N/A
19 --- 3/4 (This is such a perfect match, it is used internationally for automobile wheel nuts)
20 --- N/A
21 --- N/A
22t --- 7/8

32 --- 1-1/4 If memory serves me well, this is the size of the hub nut on the rear axle of Volks Wagons before '68 or so.

That has 7 metric sizes throughout the range not covered by an SAE wrench set.
3/16 would be tight on a 5mm, neither size is included with most sets.
Three common SAE sizes, 3/8, 11/16 and 15/16 are not covered by the metric sizes.

As for drill sizes, pick up an old metal drill index (box). They usually have the screw sizes and tap drill sizes on the front row of bit holders. For wood screws the inside of the lid serves as my note pad.

Maybe a picture is in order if my camera makes it out to the shop today.

jtk

[Kent A Bathurst]

The US is a crazy mix of metric and imperial.

Shoot - worse than that, Daniel - there was a period when all the domestic machinery guys were racing overseas, and production there started up before they had completed a 100% redesign. If you have a machine from that time period - especially Delta, and some PM - there is a mix of imperial and metric on the same doggone machine. Trust me - I gots those things staring at me right now.

For adjustment spots, I tossed a bunch of rare earth disc magnets against the cabinet/frames, and got enough duplicates so there is a combo wrench or allen key stuck to the machine at each spot. A mix of the two types, but I don't have to bring all of everything and jump back and forth as I try to find the right tool.

[Kent A Bathurst]

That's a darn useful looking gauge. Where'd you find it?

Daniel - my neighborhood Ace and my near-by BORG have them in the fasteners aisle.

[Dan Clark]

Another option is this guy: http://www.amazon.com/Bolt-Thread-Checker-Inch-Metric/dp/B003FJW0GK/ref=sr_1_2?ie=UTF8&qid=1423080427&sr=8-2&keywords=screw+gauge . Unlike many of of the others, this let's you test screws and nuts. It has the common sizes in imperial and metric.

If you need a wider range, they have separate units that contain imperial only or metric only in a wider range.

Dan.

[Hilton Ralphs]

http://www.woodmagazine.com/woodworking-tips/techniques/free-woodworking-charts/?page=4

If you open the link above, you can download a chart graphically showing woodscrew sizes.
This is great thanks.


I suggest one of these if you are a visual type of person. I have several extras, PM me if you want one.

I have sent you a PM, much appreciated.



Straight threaded fasteners are commonly called nuts and bolts. a 10-32 nut and bolt would be a #10 bolt with 32 threads per inch.
I think what Lee Valley is suggesting is that one should use machines screws (essentially a bolt with a screw head) instead of wood screws for more holding power, especially with small hinges.

So let's say the screws required for a hinge are a #6. Normally you would drill a hole with one of those tapered drill/countersink bits of the correct size. Lee Valley says substitute the wood screw for a machine screw. So do I assume that I need to use the #6-32 tap/drill set to cut the hole and then get nice brass 6-32 machine screws?

So a #8 wood screw would be substituted for a 8-32 machine screw with the hole cut with the appropriate tap/drill set? Etc, etc, etc.

Is it as simple as this?


They have a device we can buy now that we can screw a nut on or a bolt into that will identify the size and thread. I need one for metric bolts and will probably will buy one.
I have one of those in Imperial :). Particularly useful for working out what bolts or nuts are required for a lot of the old Stanley/Record tools.

[John Gornall]

Hilton, next time you order from Lee Valley get one of these:

http://www.leevalley.com/en/hardware/page.aspx?p=40057&cat=3,41306,41330,40057

All taps from 2-56 to 1/4 20 with tap drills and clearance drills

Great reference.

[Hilton Ralphs]

Thanks John, those are the ones I'm looking at.

[Edward Clarke]

I spoke somewhat in error. I don't think I've ever seen a 10-32 bolt.

10-32 screws/bolts are used in computer rack and panel systems. I use a lot of them in my business.

[lowell holmes]

10-32 screws/bolts are used in computer rack and panel systems. I use a lot of them in my business.

That is interesting. I'm used to 10-24 bolts used in electrical devices, don't recall seeing them elsewhere. With them being used in electrical boxes, it makes sense that you would find #10 bolts in computer items and that the fine threads be used.

[Hilton Ralphs]

I suggest one of these if you are a visual type of person. I have several extras, PM me if you want one.

http://www.4custom.com/e/Bolt%20Gauge%20Green%20Front.jpg

Short follow up to say that the above Bolt Gauge arrived safely in South Africa. Big heads up to Steve for kindly sending this to me. I find woodworkers (especially over here) to be the most friendliest and helpful bunch of people.

Thank you!

[Steve Rozmiarek]

You are welcome Hilton, hope it's slightly useful at least!

[Eric Brown]

Hi Hilton. The sizes of sheet metal is roughly based on how many sheets stack up to 1" thick. I say roughly because there are ferrous and non-ferrous sizes that are slightly different. Wire gages are also roughly based on the same principle. That is why the numbers get smaller as the size gets larger. Screws are typically made from wire or rod and the size is based on the material used. To make matters even more strange, our pipe sizes are based on lead pipes. When they started making them out of steel the wall thickness could be thinner than the lead ones. Then they made different thicknesses of the steel pipe and called them schedules. Example: A schedule 80 is much thicker (about twice) as a schedule 40. So our nominal pipe size doesn't even match inside or outside measurements. Tubing is closer, but there are still different wall thicknesses. Even England used the inch system as can be seen on antique tools. I worked on a Henry Brown brace (Sheffield) that had a 1/4-18 left handed thread. As I had to make a new nut, it took a while to find a tap supplier for this. I read once that the threads used for screws and bolts have been made in almost every pitch at one time or another. Because of demand, certain sizes became standard usually with a fine and coarse version. Nails are another matter. Hope this helps a little.

[Hilton Ralphs]

Thanks Eric!

I understand more why most of the world moved to the Metric system.