# M2 tap drill size

The tap drill for an M2 × 0.4 metric coarse thread is 1.6 mm (0.0630 in). It leaves about 77 % thread, the normal range for steel.

## Drill options for M2 × 0.4

| Drill | Inch | Thread % |
|---|---|---|
| 1.5 mm | 0.0591 | 96 % |
| 1.6 mm | 0.0630 | 77 % |
| 1.7 mm | 0.0669 | 58 % |

## M2 thread data

- Thread: M2 × 0.4 (coarse)
- Pitch: 0.4 mm
- Tap drill: 1.6 mm (0.0630 in)
- Thread engagement: 77 %
- Clearance hole (ISO 273): 2.2 close, 2.4 normal, 2.6 loose (mm)

## Method

Thread % = 76.98 × (D − drill) / P = 76.98 × 0.4 / 0.4 = 77 %. Aim for 65–75 % in steel, 75–85 % in aluminium, brass and plastics.

## FAQ

**What size drill for an M2 × 0.4 tap?**
Use a 1.6 mm drill. It leaves about 77 % thread engagement.

**What is 1.6 mm in inches?**
1.6 mm is 0.0630 inch.

**What size clearance hole for M2?**
ISO 273 gives 2.2 mm for a close fit, 2.4 mm normal and 2.6 mm loose.

Source page: https://machinistcharts.com/tap-drill/m2/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)