Metric coarse
Tap drill 26.5 mm for a M30 × 3.5 thread — major Ø 30 mm, pitch 3.5 mm (7.26 TPI).
Profile
| Designation | M30 × 3.5 |
|---|---|
| Major (outside) diameter | 30 mm · 1.1811" |
| Pitch | 3.5 mm · 7.26 TPI |
| Pitch diameter | 27.727 mm · 1.0916" |
| Minor diameter (external) | 25.706 mm · 1.012" |
| Minor diameter (internal) | 26.211 mm · 1.0319" |
| Recommended tap drill | 26.5 mm · ≈77% thread |
| Clearance hole | Close 31 · Normal 33 · Loose 35 mm |
| Hex head (across flats) | 46 mm |
| Socket key (across flats) | 22 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 | 560.6 mm² | 243.86 kN | 1463.1 N·m |
| Class 10.9 | 560.6 mm² | 348.96 kN | 2093.8 N·m |
| Class 12.9 | 560.6 mm² | 407.83 kN | 2447 N·m |
For a M30 × 3.5 thread, drill the hole with a 26.5 mm tap drill (26.5 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 30 mm and a pitch of 3.5 mm (7.26 TPI).
To pass a M30 × 3.5 bolt through a part rather than thread it, use a clearance hole: Close 31 · Normal 33 · Loose 35 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.
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