Metric fine
Tap drill 26 mm for a M27 × 1.0 thread — major Ø 27 mm, pitch 1 mm (25.4 TPI).
Profile
| Designation | M27 × 1.0 |
|---|---|
| Major (outside) diameter | 27 mm · 1.063" |
| Pitch | 1 mm · 25.4 TPI |
| Pitch diameter | 26.351 mm · 1.0374" |
| Minor diameter (external) | 25.773 mm · 1.0147" |
| Minor diameter (internal) | 25.918 mm · 1.0204" |
| Recommended tap drill | 26 mm · ≈77% thread |
| Clearance hole | Close 28 · Normal 30 · Loose 32 mm |
| Hex head (across flats) | 41 mm |
| Socket key (across flats) | 19 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 | 533.5 mm² | 232.05 kN | 1253.1 N·m |
| Class 10.9 | 533.5 mm² | 332.08 kN | 1793.2 N·m |
| Class 12.9 | 533.5 mm² | 388.09 kN | 2095.7 N·m |
For a M27 × 1.0 thread, drill the hole with a 26 mm tap drill (26 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 27 mm and a pitch of 1 mm (25.4 TPI).
To pass a M27 × 1.0 bolt through a part rather than thread it, use a clearance hole: Close 28 · Normal 30 · Loose 32 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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