Metric fine
Tap drill 25 mm for a M27 × 2.0 thread — major Ø 27 mm, pitch 2 mm (12.7 TPI).
Profile
| Designation | M27 × 2.0 |
|---|---|
| Major (outside) diameter | 27 mm · 1.063" |
| Pitch | 2 mm · 12.7 TPI |
| Pitch diameter | 25.701 mm · 1.0119" |
| Minor diameter (external) | 24.546 mm · 0.9664" |
| Minor diameter (internal) | 24.835 mm · 0.9778" |
| Recommended tap drill | 25 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 | 495.7 mm² | 215.65 kN | 1164.5 N·m |
| Class 10.9 | 495.7 mm² | 308.6 kN | 1666.4 N·m |
| Class 12.9 | 495.7 mm² | 360.65 kN | 1947.5 N·m |
For a M27 × 2.0 thread, drill the hole with a 25 mm tap drill (25 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 2 mm (12.7 TPI).
To pass a M27 × 2.0 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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