7/8-9 UNC tap drill size

49/64 drill — 0.7656 in / 19.45 mm (76% thread)

Major Ø 0.8750 in · 9 threads per inch · coarse series. The chart pick targets 75% thread; nearby standard drills:

Drill	Decimal (in)	mm	Thread %
51/64	0.7969	20.24	54%
25/32	0.7813	19.84	65%
49/64	0.7656	19.45	76%
3/4	0.7500	19.05	87%

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: 7/8-14 UNF