# M10 tap drill size

The tap drill for an M10 × 1.5 metric coarse thread is 8.5 mm (0.3346 in). It leaves about 77 % thread, the normal range for steel.

## Drill options for M10 × 1.5

| Drill | Inch | Thread % |
|---|---|---|
| 8.3 mm | 0.3268 | 87 % |
| 8.4 mm | 0.3307 | 82 % |
| 8.5 mm | 0.3346 | 77 % |
| 8.6 mm | 0.3386 | 72 % |
| 8.7 mm | 0.3425 | 67 % |

## M10 thread data

- Thread: M10 × 1.5 (coarse)
- Pitch: 1.5 mm
- Tap drill: 8.5 mm (0.3346 in)
- Thread engagement: 77 %
- Clearance hole (ISO 273): 10.5 close, 11 normal, 12 loose (mm)

## Method

Thread % = 76.98 × (D − drill) / P = 76.98 × 1.5 / 1.5 = 77 %. Aim for 65–75 % in steel, 75–85 % in aluminium, brass and plastics.

## FAQ

**What size drill for an M10 × 1.5 tap?**
Use a 8.5 mm drill. It leaves about 77 % thread engagement.

**What is 8.5 mm in inches?**
8.5 mm is 0.3346 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/m10/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)