# M10x1.25 tap drill size

The tap drill for an M10 × 1.25 metric fine thread is 8.8 mm (0.3465 in). It leaves about 74 % thread, the normal range for steel.

## Drill options for M10 × 1.25

| Drill | Inch | Thread % |
|---|---|---|
| 8.6 mm | 0.3386 | 86 % |
| 8.7 mm | 0.3425 | 80 % |
| 8.8 mm | 0.3465 | 74 % |
| 8.9 mm | 0.3504 | 68 % |
| 9 mm | 0.3543 | 62 % |

## M10x1.25 thread data

- Thread: M10 × 1.25 (fine)
- Pitch: 1.25 mm
- Tap drill: 8.8 mm (0.3465 in)
- Thread engagement: 74 %
- Clearance hole (ISO 273): 10.5 close, 11 normal, 12 loose (mm)

## Method

Thread % = 76.98 × (D − drill) / P = 76.98 × 1.2 / 1.25 = 74 %. Aim for 65–75 % in steel, 75–85 % in aluminium, brass and plastics.

## FAQ

**What size drill for an M10 × 1.25 tap?**
Use a 8.8 mm drill. It leaves about 74 % thread engagement.

**What is 8.8 mm in inches?**
8.8 mm is 0.3465 inch.

**What size clearance hole for M10?**
ISO 273 gives 10.5 mm for a close fit, 11 mm normal and 12 mm loose.

**How tight should an M10 bolt be?**
About 50 N·m for class 8.8 with dry threads.

Source page: https://machinistcharts.com/tap-drill/m10x1-25/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)