ThreadRef

Sizes · Metric (ISO)

Metric fine

M42 × 3.0

Tap drill 39 mm for a M42 × 3.0 thread — major Ø 42 mm, pitch 3 mm (8.47 TPI).

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Tap drill
39 mm
39 mm · ≈77% thread

Profile

Thread form & key diameters

Major Ø 42 mmP 3 mm60°Minor Ø 38.319 mm · Pitch Ø 40.052 mmM42 × 3.08.47 TPI · 60° form

Dimensions

DesignationM42 × 3.0
Major (outside) diameter42 mm · 1.6535"
Pitch3 mm · 8.47 TPI
Pitch diameter40.052 mm · 1.5768"
Minor diameter (external)38.319 mm · 1.5086"
Minor diameter (internal)38.753 mm · 1.5257"
Recommended tap drill39 mm · ≈77% thread
Clearance holeClose 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 / classStress areaPreloadTorque
Class 8.81206 mm²524.6 kN4406.6 N·m
Class 10.91206 mm²750.72 kN6306 N·m
Class 12.91206 mm²877.35 kN7369.7 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 × 3.0?

For a M42 × 3.0 thread, drill the hole with a 39 mm tap drill (39 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 3 mm (8.47 TPI).

To pass a M42 × 3.0 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 × 2.0Tap 40 mmØ 42 mm · pitch 2 mmM42 × 4.0Tap 38 mmØ 42 mm · pitch 4 mmM42 × 4.5Tap 37.5 mmØ 42 mm · pitch 4.5 mm

Nearby sizes

More metric fine threads

M42 × 2.0Tap 40 mmØ 42 mm · pitch 2 mmM42 × 4.0Tap 38 mmØ 42 mm · pitch 4 mmM39 × 2.0Tap 37 mmØ 39 mm · pitch 2 mmM39 × 3.0Tap 36 mmØ 39 mm · pitch 3 mmM45 × 1.5Tap 43.5 mmØ 45 mm · pitch 1.5 mmM45 × 2.0Tap 43 mmØ 45 mm · pitch 2 mmM45 × 3.0Tap 42 mmØ 45 mm · pitch 3 mmM45 × 4.0Tap 41 mmØ 45 mm · pitch 4 mm