Hank, 9/32" is a size just a hair larger than across the corners of the 1/4" hex bit (which is 1/4" across the flats). A 1/4" hex bit will NOT fit in a 1/4" diameter hole.

That (9/32") not a snug fit but there's no slop. If you turn it over and shake it they will all fall out. If you don't shake I daresay most will fall out.

Here's the dope: The geometry-based math says the distance across the flats is .250/Cos(30) which is .28865"

Manufacturing being what it is there is probably some small radius on the corners.

I measured a few just a minute ago and they run about .280-.285" probably because they break the sharp edge for that radius I mentioned.

I suggested an Number series "L" bit at .290 will work. And a 9/32 is .2815" Remember it only touches at two or six points, not 100% of the circumference (like a round shank), so its not hard to get out even if its a pretty close fit. So I find 9/32 is quite good.

I see I posted this project twice. Oh well. Getting forgetful.

That (9/32") not a snug fit but there's no slop. If you turn it over and shake it they will all fall out. If you don't shake I daresay most will fall out.

Here's the dope: The geometry-based math says the distance across the flats is .250/Cos(30) which is .28865"

Manufacturing being what it is there is probably some small radius on the corners.

I measured a few just a minute ago and they run about .280-.285" probably because they break the sharp edge for that radius I mentioned.

I suggested an Number series "L" bit at .290 will work. And a 9/32 is .2815" Remember it only touches at two or six points, not 100% of the circumference (like a round shank), so its not hard to get out even if its a pretty close fit. So I find 9/32 is quite good.

I see I posted this project twice. Oh well. Getting forgetful.

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