6-48 Tap Drill Size and Drill Bit Guide

Use a #32 drill bit

6-48 · 0.1160 in / 2.95 mm · ~75% thread

6-48 is the fine-pitch version of the #6 screw thread, used where vibration resistance matters — optics, instruments and firearms work. A #32 bit is the standard tap drill for a 75% thread.

At a glance

Tap drill	#32
Inches	0.1160 in
Millimetres	2.95 mm
Major diameter	0.1380 in
Pitch	0.0208 in
Threads per inch	48

Why this size

6-48 tap drill: drillØ = major − (pitch × 0.75) = 0.1380 − (0.0208 × 0.75) = 0.1224 in → next standard drill #32 (0.1160 in / 2.95 mm)

Do not confuse 6-48 fine with the common 6-32 coarse, which uses the smaller #36 bit. Fine pitch leaves more material in the threads, so the tap pulls harder — back off often to clear chips.