ThreadRef

Sizes · Metric (ISO)

Metric coarse

M33 × 3.5

Tap drill 29.5 mm for a M33 × 3.5 thread — major Ø 33 mm, pitch 3.5 mm (7.26 TPI).

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Tap drill
29.5 mm
29.5 mm · ≈77% thread

Profile

Thread form & key diameters

Major Ø 33 mmP 3.5 mm60°Minor Ø 28.706 mm · Pitch Ø 30.727 mmM33 × 3.57.26 TPI · 60° form

Dimensions

DesignationM33 × 3.5
Major (outside) diameter33 mm · 1.2992"
Pitch3.5 mm · 7.26 TPI
Pitch diameter30.727 mm · 1.2097"
Minor diameter (external)28.706 mm · 1.1302"
Minor diameter (internal)29.211 mm · 1.15"
Recommended tap drill29.5 mm · ≈77% thread
Clearance holeClose 34 · Normal 36 · Loose 38 mm
Hex head (across flats)50 mm
Socket key (across flats)24 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 8.8693.6 mm²301.7 kN1991.2 N·m
Class 10.9693.6 mm²431.74 kN2849.5 N·m
Class 12.9693.6 mm²504.56 kN3330.1 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 M33 × 3.5?

For a M33 × 3.5 thread, drill the hole with a 29.5 mm tap drill (29.5 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 33 mm and a pitch of 3.5 mm (7.26 TPI).

To pass a M33 × 3.5 bolt through a part rather than thread it, use a clearance hole: Close 34 · Normal 36 · Loose 38 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 M33 threads

M33 × 1.5Tap 31.5 mmØ 33 mm · pitch 1.5 mmM33 × 2.0Tap 31 mmØ 33 mm · pitch 2 mmM33 × 3.0Tap 30 mmØ 33 mm · pitch 3 mm

Nearby sizes

More metric coarse threads

M30 × 3.5Tap 26.5 mmØ 30 mm · pitch 3.5 mmM36 × 4.0Tap 32 mmØ 36 mm · pitch 4 mmM27 × 3.0Tap 24 mmØ 27 mm · pitch 3 mmM39 × 4.0Tap 35 mmØ 39 mm · pitch 4 mmM24 × 3.0Tap 21 mmØ 24 mm · pitch 3 mmM42 × 4.5Tap 37.5 mmØ 42 mm · pitch 4.5 mmM22 × 2.5Tap 19.5 mmØ 22 mm · pitch 2.5 mmM45 × 4.5Tap 40.5 mmØ 45 mm · pitch 4.5 mm