M10 × 1.25 Thread
The chart recommendation gives approximately 73.9% thread engagement — the conventional target for average materials. It is not the only valid choice; see the options below.
Specification
| Designation | M10 × 1.25 |
|---|---|
| Thread family | ISO metric fine |
| Nominal size | M10 |
| Basic major diameter | 0.3937″ / 10 mm |
| Pitch | 1.25 mm |
| Recommended tap drill | 8.8 mm (0.3465″ / 8.8 mm) |
Tap drill options by thread engagement
Any of these standard drills produces a usable engagement for M10 × 1.25; smaller drills give stronger threads but higher tapping torque. Percentages use the conventional approximation (60° thread form).
| Drill | Decimal in | mm | Approx. engagement |
|---|---|---|---|
| 8.7 mm | 0.3425 | 8.7 | 80.1% |
| 11/32″ | 0.3438 | 8.731 | 78.1% |
| 8.8 mm — chart recommendation | 0.3465 | 8.8 | 73.9% |
| S | 0.3480 | 8.839 | 71.5% |
| 8.9 mm | 0.3504 | 8.9 | 67.7% |
| 9 mm | 0.3543 | 9 | 61.6% |
Nearest drills to the tap drill in other systems
| Drill | Size | vs 8.8 mm | Resulting engagement |
|---|---|---|---|
| 11/32″ | 0.3438″ / 8.731 mm | −0.069 mm | 78.1% |
| S | 0.3480″ / 8.839 mm | +0.039 mm | 71.5% |
Clearance holes
For a bolt or screw of this size to pass through freely. ISO 273 series (fine/medium/coarse), shown as close, normal, and loose.
Hex bolt & nut dimensions
For a standard hex bolt (ISO 4014/4017) and style-1 nut (ISO 4032) in this size.
| Wrench / socket size (bolt head) | 16 mm — legacy DIN: 17 mm |
|---|---|
| Head height | 6.4 mm |
| Nut thickness | 8.4 mm |
| Compatible nut | M10 × 1.25 hex nut |
Basic (nominal) dimensions. See the wrench & socket size charts for all sizes and the metric ↔ SAE socket comparison.
Related threads
- M10 × 1.5 — same nominal size, 1.5 mm pitch (ISO metric coarse) · compare
- M10 × 1 — same nominal size, 1 mm pitch (ISO metric fine) · compare
- M10 × 1 — next size down in metric-fine
- M12 × 1.25 — next size up in metric-fine