I was going to buy a 5/16 (cutter diameter) spiral upcut bit to cut
some slots in plywood. I see some with 5/16 shanks for ~$15, and some
with 1/2 shanks in $30-40 range. Could the 5/16 shank be used in a 1/4
Let's see. 5/16 = 5 of the sixteenths. 1/4 = only 4 of the sixteenths.
The size of the hole is only 4 of the sixteenths so unless you have a really
big hammer, it won't fit. You need a collet with one more sixteenths in it.
And no, I won't even joke about the 1/2" collet and duct tape.
Yes 5/16" exists and is a very common size.
Leigh sell this bit for their jigs.
Also, for those that use metric sized shanks, 8mm is extremely common. 8mm
is within 1.5/10,000th of an inch of being 5/16".
8mm = 0.3149606299 inches. 5/16" = .315
Due to the design of most router collets, this is far to much variation to
call interchangeable. Using collets everyday of all sizes and designs, I
would stear clear of using something with that kind of mismatch in most
collet designs. You may well get away with it but I wouldn't chance it.
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