3/4-10 UNC tap drill size

21/32 drill — 0.6563 in / 16.67 mm (72% thread)

Major Ø 0.7500 in · 10 threads per inch · coarse series. The chart pick targets 75% thread; nearby standard drills:

Drill	Decimal (in)	mm	Thread %
43/64	0.6719	17.07	60%
21/32	0.6563	16.67	72%
41/64	0.6406	16.27	84%
5/8	0.6250	15.88	96%

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: 3/4-16 UNF