Metric coarse
Tap drill 2.5 mm for a M3 × 0.5 thread — major Ø 3 mm, pitch 0.5 mm (50.8 TPI).
Profile
| Designation | M3 × 0.5 |
|---|---|
| Major (outside) diameter | 3 mm · 0.1181" |
| Pitch | 0.5 mm · 50.8 TPI |
| Pitch diameter | 2.675 mm · 0.1053" |
| Minor diameter (external) | 2.387 mm · 0.094" |
| Minor diameter (internal) | 2.459 mm · 0.0968" |
| Recommended tap drill | 2.5 mm · ≈77% thread |
| Clearance hole | Close 3.2 · Normal 3.4 · Loose 3.6 mm |
| Hex head (across flats) | 5.5 mm |
| Socket key (across flats) | 2.5 mm |
ISO 273 clearance holes (fine / medium / coarse).
Target preload is 75% of proof load; torque is estimated from T = K · F · d.
| Grade / class | Stress area | Preload | Torque |
|---|---|---|---|
| Class 8.8 | 5 mm² | 2.19 kN | 1.31 N·m |
| Class 10.9 | 5 mm² | 3.13 kN | 1.88 N·m |
| Class 12.9 | 5 mm² | 3.66 kN | 2.2 N·m |
For a M3 × 0.5 thread, drill the hole with a 2.5 mm tap drill (2.5 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 3 mm and a pitch of 0.5 mm (50.8 TPI).
To pass a M3 × 0.5 bolt through a part rather than thread it, use a clearance hole: Close 3.2 · Normal 3.4 · Loose 3.6 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.
Nearby sizes