Project Squirrel

[overkill]

Sorry, a 5/16" hole is too small. The tap will be cutting more than 100% of the thread depth, which is an excellent way to snap it. You are looking at the hole size for a UNC 3/8-16 thread.

[Maxamuslead]

derp nevermind didn't read it correctly.
http://www.carbidedepot.com/formulas-tap-standard.htm

Sorry, a 5/16" hole is too small. The tap will be cutting more than 100% of the thread depth, which is an excellent way to snap it. You are looking at the hole size for a UNC 3/8-16 thread.

Reading more into it wouldn't a m8/m9 size hole work

(my working. 3/8 unf requires a "Q" sized drilled hole which is 0.332 in which is 8.4328mm)