M45 × 4.0 — Tap Drill, Dimensions & Torque

Profile

Thread form & key diameters

Dimensions

Designation	M45 × 4.0
Major (outside) diameter	45 mm · 1.7717"
Pitch	4 mm · 6.35 TPI
Pitch diameter	42.402 mm · 1.6694"
Minor diameter (external)	40.093 mm · 1.5784"
Minor diameter (internal)	40.67 mm · 1.6012"
Recommended tap drill	41 mm · ≈77% thread
Clearance hole	Close 46 · Normal 48 · Loose 51 mm
Hex head (across flats)	70 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	1336.2 mm²	581.26 kN	5231.3 N·m
Class 10.9	1336.2 mm²	831.8 kN	7486.2 N·m
Class 12.9	1336.2 mm²	972.1 kN	8748.9 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 M45 × 4.0?

For a M45 × 4.0 thread, drill the hole with a 41 mm tap drill (41 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 45 mm and a pitch of 4 mm (6.35 TPI).

To pass a M45 × 4.0 bolt through a part rather than thread it, use a clearance hole: Close 46 · Normal 48 · Loose 51 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 M45 threads

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 × 4.5Tap 40.5 mmØ 45 mm · pitch 4.5 mm

Nearby sizes

More metric fine threads

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 M42 × 2.0Tap 40 mmØ 42 mm · pitch 2 mm M42 × 3.0Tap 39 mmØ 42 mm · pitch 3 mm M42 × 4.0Tap 38 mmØ 42 mm · pitch 4 mm M48 × 1.5Tap 46.5 mmØ 48 mm · pitch 1.5 mm M48 × 2.0Tap 46 mmØ 48 mm · pitch 2 mm