7/8-14 UNF tap drill size

13/16 drill — 0.8125 in / 20.64 mm (67% thread)

Major Ø 0.8750 in · 14 threads per inch · fine series. The chart pick targets 75% thread; nearby standard drills:

Drill	Decimal (in)	mm	Thread %
53/64	0.8281	21.03	51%
13/16	0.8125	20.64	67%
51/64	0.7969	20.24	84%
25/32	0.7813	19.84	101%

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, coarse series: 7/8-9 UNC