# M6 tap drill size

The tap drill for an M6 × 1 metric coarse thread is 5 mm (0.1969 in). It leaves about 77 % thread, the normal range for steel.

## Drill options for M6 × 1

| Drill | Inch | Thread % |
|---|---|---|
| 4.8 mm | 0.1890 | 92 % |
| 4.9 mm | 0.1929 | 85 % |
| 5 mm | 0.1969 | 77 % |
| 5.1 mm | 0.2008 | 69 % |
| 5.2 mm | 0.2047 | 62 % |

## M6 thread data

- Thread: M6 × 1 (coarse)
- Pitch: 1 mm
- Tap drill: 5 mm (0.1969 in)
- Thread engagement: 77 %
- Clearance hole (ISO 273): 6.4 close, 6.6 normal, 7 loose (mm)

## Method

Thread % = 76.98 × (D − drill) / P = 76.98 × 1 / 1 = 77 %. Aim for 65–75 % in steel, 75–85 % in aluminium, brass and plastics.

## FAQ

**What size drill for an M6 × 1 tap?**
Use a 5 mm drill. It leaves about 77 % thread engagement.

**What is 5 mm in inches?**
5 mm is 0.1969 inch.

**What size clearance hole for M6?**
ISO 273 gives 6.4 mm for a close fit, 6.6 mm normal and 7 mm loose.

**How tight should an M6 bolt be?**
About 11 N·m for class 8.8 with dry threads.

Source page: https://machinistcharts.com/tap-drill/m6/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)