# Homemade Tools > Basic Homemade Tools and Tips >  Hex wrench size chart

## mklotz

Instead of always trying several wrenches to find the correct size I decided to make a little chart to stick to the front of the tool box. 

HEX WRENCH SIZES

A = SAE number
B = hex wrench size for socket head cap screw
C = hex wrench size for set screw



```
A	B		C

0	0.050		0.028
1	1/16		0.028
2	5/64		0.035
3	5/64		0.050
4	3/32		0.050
5	3/32		1/16
6	7/64		1/16
8	9/64		5/64
10	5/32		3/32
```

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Paul Jones (Apr 8, 2017),

Seedtick (Apr 9, 2017),

Toolmaker51 (Apr 10, 2017)

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## pfredX1

I did not know about the SAE numbers. I just made a holder with every size hex wrench I have in it, in ascending order. SAE and metric. So if none of those fit, then I don't have the Allen key.

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Moby Duck (Apr 9, 2017)

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## Frank S

This chart may be of some help as additionally to the SAE sizes it lists fractional as well as metric but not the set screws

Socket Head Cap Screw Size Chart
Also if you visit that page and click on 1 of the menus it will take you to a page for downloading their 80 page book of fastener dimensions
Sorry they are a fastener company and will want contact info

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## mklotz

> I did not know about the SAE numbers. I just made a holder with every size hex wrench I have in it, in ascending order. SAE and metric. So if none of those fit, then I don't have the Allen key.



I think you've missed the point. The idea is to avoid the need to try successive wrenches for a fit. Assuming you know the specification of the SHCS or set screw, just look at the chart and select the wrench it shows.

For example, if you're using a 6-32 cap screw, the chart says you need the 7/64" hex wrench. A 4-40 set screw will require the 0.050" wrench.

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Paul Jones (Aug 25, 2017)

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## mklotz

> This chart may be of some help as additionally to the SAE sizes it lists fractional as well as metric but not the set screws
> 
> Socket Head Cap Screw Size Chart



For the fractional SHCS, I simply remember the rule(s)...

If less than 1/2 subtract 1/16 from the screw size to find wrench size
else
If less than 1 subtract 1/8 from the screw size to find wrench size

I've never seen a 1" SHCS much less anything larger but there are similar consistencies as one goes up into those Brobdingnagian sizes.

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metric_taper (Apr 10, 2017),

Paul Jones (Aug 25, 2017)

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## Frank S

Marv I think the largest hex key that I own is 1", and have only used it on hydraulic plugs. The largest hex key I've even seen was 3" and must have weighed 50 lbs I don't even want to try an visualize what that was used for But hey I used to have a 44 lb sledge hammer that a friend made for me because I was always saying if I just had a bigger hammer this job would be easy.

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Paul Jones (Aug 25, 2017)

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## Toolmaker51

44 pound sledge? I think the term is a 'maul'. Same thing. 
Either is a putter in Texas.

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## pfredX1

That's not how I typically deal with hardware. For me it is more like there it is, find something that fits it.

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## Ed Weldon

Marv - Thanks for the little hex key size chart. It'll be easy to print a whole slew of them on some good photo paper and stick them in place with Eileen's Tacky glue. BTW, that heavy weight inkjet photo paper is great for making really permanent lables using hand writing with sharpie pens. Sharpies on non absorbant surfaces go on so thin that they fade after a few years. But the porosity of inkjet paper lets the dye go deep and permanent. Ald if tacky glue isn't good enough go with pliobond for the label. (like on a glass jar). I've become real careful about marking the contents of any container that doesn't have a clear label describing the actual contents. In professional shops the laws and rules are real cleat about this sort of thing. For a home shop in the hands of a people smart enough to be machinists you don't necessarily have to be OSHA compliant but clear info on container contents is a good plan, especially as you a age and tend to forget more easily. Ed Weldon
One othe point about paint on hex keys. I tried that first and the shrink tube approach is faster and looks a lot better if you have lots of hex key sets to mark as well as a cabinet full of spares.
Ed Weldon

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