ISO metric · fine

M10 × 1 tap drill size

For general work, OSG suggests 65–70% of full thread. Harder materials and deep holes want less; the calculator sets it from your material.

Cut tap

9.1 mm

0.3583" · 69% thread

Form tap

9.5 mm

0.3740" · 74% thread

Or 3/8 (0.3750") for 70%

Open M10 × 1 in the calculator

Pick your material for its % of thread, tapping RPM and the rigid-tap code.

Thread dimensions

Major Ø: 10.000 mm (0.3937")
Pitch: 1 mm
Pitch Ø (basic): 9.350 mm (0.3681")
Minor Ø (internal, basic): 8.917 mm (0.3511")
Thread depth (internal): 0.541 mm (0.0213")

Basic sizes of the 60° form. Tolerance classes (6H) set the limits around them.

Cut tap drills

For a cutting (fluted or spiral) tap. Every standard drill from 50% to 85% thread; suggested rows are in the 65–70% band.

Cut tap drills for M10 × 1
Drill	Ø in	Ø mm	Thread
8.9 mm	0.3504	8.90	85%
9 mm	0.3543	9.00	77%
Tsuggested	0.3580	9.09	70%
9.1 mmsuggested	0.3583	9.10	69%
23/64suggested	0.3594	9.13	67%
9.2 mm	0.3622	9.20	62%
9.3 mm	0.3661	9.30	54%
U	0.3680	9.35	50%

Form tap drills

A form (roll) tap displaces metal instead of cutting it, so it needs a bigger hole. Every standard drill from 50% to 85% thread; suggested rows are in the 65–70% band.

Form tap drills for M10 × 1
Drill	Ø in	Ø mm	Thread
9.5 mm	0.3740	9.50	74%
3/8suggested	0.3750	9.53	70%
V	0.3770	9.58	62%
9.6 mm	0.3780	9.60	59%

3-wire measurement

Best wire size: 0.577 mm (0.0227")
Over wires, at basic pitch Ø: 10.217 mm (0.4022")

For the external thread (the screw). The best wire touches the flanks at the pitch diameter.

Sources

ISO 261 / ISO 262 — ISO general purpose metric screw threads: general plan and selected sizes
OSG — Tap drill size and pitch diameter limit chart (formula, suggested % of full thread)
Cutting Tool Engineering — "Threads will roll": form tap hole size = D − 0.0068 × % / TPI
ASME B94.11M — Twist drills (fractional, number, letter and metric sizes)
NIST (NBS) Letter Circular 23 and Pratt & Whitney — three-wire thread measurement, best wire size