1-3/8-12 UNF tap drill size

1-19/64 drill — 1.2969 in / 32.94 mm (72% thread)

Major Ø 1.3750 in · 12 threads per inch · fine series. The chart pick targets 75% thread; nearby standard drills:

Drill	Decimal (in)	mm	Thread %
1-5/16	1.3125	33.34	58%
1-19/64	1.2969	32.94	72%
1-9/32	1.2813	32.54	87%
1-17/64	1.2656	32.15	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: 1-3/8-6 UNC