1/2-13 UNC tap drill size

27/64 drill — 0.4219 in / 10.72 mm (78% thread)

Major Ø 0.5000 in · 13 threads per inch · coarse series. The chart pick targets 75% thread; nearby standard drills:

Drill	Decimal (in)	mm	Thread %
7/16	0.4375	11.11	63%
27/64	0.4219	10.72	78%
Z	0.4130	10.49	87%
13/32	0.4063	10.32	94%

Cut taps only — roll-form taps need a larger hole. 65–75% suits general work; drop toward 55% in tough material. Verify before you cut.

Same size, fine series: 1/2-20 UNF