# M5 tap drill size

The tap drill for an M5 × 0.8 metric coarse thread is 4.2 mm (0.1654 in). It leaves about 77 % thread, the normal range for steel.

## Drill options for M5 × 0.8

| Drill | Inch | Thread % |
|---|---|---|
| 4 mm | 0.1575 | 96 % |
| 4.1 mm | 0.1614 | 87 % |
| 4.2 mm | 0.1654 | 77 % |
| 4.3 mm | 0.1693 | 67 % |
| 4.4 mm | 0.1732 | 58 % |

## M5 thread data

- Thread: M5 × 0.8 (coarse)
- Pitch: 0.8 mm
- Tap drill: 4.2 mm (0.1654 in)
- Thread engagement: 77 %
- Clearance hole (ISO 273): 5.3 close, 5.5 normal, 5.8 loose (mm)

## Method

Thread % = 76.98 × (D − drill) / P = 76.98 × 0.8 / 0.8 = 77 %. Aim for 65–75 % in steel, 75–85 % in aluminium, brass and plastics.

## FAQ

**What size drill for an M5 × 0.8 tap?**
Use a 4.2 mm drill. It leaves about 77 % thread engagement.

**What is 4.2 mm in inches?**
4.2 mm is 0.1654 inch.

**What size clearance hole for M5?**
ISO 273 gives 5.3 mm for a close fit, 5.5 mm normal and 5.8 mm loose.

**How tight should an M5 bolt be?**
About 6.2 N·m for class 8.8 with dry threads.

Source page: https://machinistcharts.com/tap-drill/m5/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)