# M4x0.5 tap drill size

The tap drill for an M4 × 0.5 metric fine thread is 3.5 mm (0.1378 in). It leaves about 77 % thread, the normal range for steel.

## Drill options for M4 × 0.5

| Drill | Inch | Thread % |
|---|---|---|
| 3.4 mm | 0.1339 | 92 % |
| 3.5 mm | 0.1378 | 77 % |
| 3.6 mm | 0.1417 | 62 % |
| 3.7 mm | 0.1457 | 46 % |

## M4x0.5 thread data

- Thread: M4 × 0.5 (fine)
- Pitch: 0.5 mm
- Tap drill: 3.5 mm (0.1378 in)
- Thread engagement: 77 %
- Clearance hole (ISO 273): 4.3 close, 4.5 normal, 4.8 loose (mm)

## Method

Thread % = 76.98 × (D − drill) / P = 76.98 × 0.5 / 0.5 = 77 %. Aim for 65–75 % in steel, 75–85 % in aluminium, brass and plastics.

## FAQ

**What size drill for an M4 × 0.5 tap?**
Use a 3.5 mm drill. It leaves about 77 % thread engagement.

**What is 3.5 mm in inches?**
3.5 mm is 0.1378 inch.

**What size clearance hole for M4?**
ISO 273 gives 4.3 mm for a close fit, 4.5 mm normal and 4.8 mm loose.

**How tight should an M4 bolt be?**
About 3.1 N·m for class 8.8 with dry threads.

Source page: https://machinistcharts.com/tap-drill/m4x0-5/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)