M42 × 2.0 — Tap Drill, Dimensions & Torque

Profile

Thread form & key diameters

Dimensions

Designation	M42 × 2.0
Major (outside) diameter	42 mm · 1.6535"
Pitch	2 mm · 12.7 TPI
Pitch diameter	40.701 mm · 1.6024"
Minor diameter (external)	39.546 mm · 1.5569"
Minor diameter (internal)	39.835 mm · 1.5683"
Recommended tap drill	40 mm · ≈77% thread
Clearance hole	Close 43 · Normal 45 · Loose 48 mm
Hex head (across flats)	65 mm
Socket key (across flats)	32 mm

ISO 273 clearance holes (fine / medium / coarse).

Tightening torque estimate

Target preload is 75% of proof load; torque is estimated from T = K · F · d.

Grade / class	Stress area	Preload	Torque
Class 8.8	1264.4 mm²	550.02 kN	4620.2 N·m
Class 10.9	1264.4 mm²	787.1 kN	6611.6 N·m
Class 12.9	1264.4 mm²	919.86 kN	7726.8 N·m

These figures assume a nut factor of K = 0.20 (dry / as-received steel). K captures thread and head friction and can swing torque by 30% or more — a lubricated joint needs noticeably less. Change the lubrication assumption in the bolt-torque calculator.

What tap drill do I need for M42 × 2.0?

For a M42 × 2.0 thread, drill the hole with a 40 mm tap drill (40 mm — the standard D − P rule) before tapping. That produces roughly 77% thread engagement, the usual target for a strong, tappable hole. The mating bolt has a major diameter of 42 mm and a pitch of 2 mm (12.7 TPI).

To pass a M42 × 2.0 bolt through a part rather than thread it, use a clearance hole: Close 43 · Normal 45 · Loose 48 mm.

All values are generated from the standard thread formulas (ISO 68-1 / ASME B1.1) and published standard tables — not hand-entered. See the full reference.

Same diameter

Other M42 threads

M42 × 3.0Tap 39 mmØ 42 mm · pitch 3 mm M42 × 4.0Tap 38 mmØ 42 mm · pitch 4 mm M42 × 4.5Tap 37.5 mmØ 42 mm · pitch 4.5 mm

Nearby sizes

More metric fine threads

M42 × 3.0Tap 39 mmØ 42 mm · pitch 3 mm M42 × 4.0Tap 38 mmØ 42 mm · pitch 4 mm M39 × 2.0Tap 37 mmØ 39 mm · pitch 2 mm M39 × 3.0Tap 36 mmØ 39 mm · pitch 3 mm M45 × 1.5Tap 43.5 mmØ 45 mm · pitch 1.5 mm M45 × 2.0Tap 43 mmØ 45 mm · pitch 2 mm M45 × 3.0Tap 42 mmØ 45 mm · pitch 3 mm M45 × 4.0Tap 41 mmØ 45 mm · pitch 4 mm