Metric fine
Tap drill 12.75 mm for a M14 × 1.25 thread — major Ø 14 mm, pitch 1.25 mm (20.32 TPI).
Profile
| Designation | M14 × 1.25 |
|---|---|
| Major (outside) diameter | 14 mm · 0.5512" |
| Pitch | 1.25 mm · 20.32 TPI |
| Pitch diameter | 13.188 mm · 0.5192" |
| Minor diameter (external) | 12.466 mm · 0.4908" |
| Minor diameter (internal) | 12.647 mm · 0.4979" |
| Recommended tap drill | 12.75 mm · ≈77% thread |
| Clearance hole | Close 15 · Normal 15.5 · Loose 16.5 mm |
| Hex head (across flats) | 21 mm |
| Socket key (across flats) | 12 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 | 129.2 mm² | 56.21 kN | 157.4 N·m |
| Class 10.9 | 129.2 mm² | 80.44 kN | 225.2 N·m |
| Class 12.9 | 129.2 mm² | 94.01 kN | 263.2 N·m |
For a M14 × 1.25 thread, drill the hole with a 12.75 mm tap drill (12.75 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 14 mm and a pitch of 1.25 mm (20.32 TPI).
To pass a M14 × 1.25 bolt through a part rather than thread it, use a clearance hole: Close 15 · Normal 15.5 · Loose 16.5 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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