# M16 tap drill size

The tap drill for an M16 × 2 metric coarse thread is 14 mm (0.5512 in). It leaves about 77 % thread, the normal range for steel.

## Drill options for M16 × 2

| Drill | Inch | Thread % |
|---|---|---|
| 13.8 mm | 0.5433 | 85 % |
| 13.9 mm | 0.5472 | 81 % |
| 14 mm | 0.5512 | 77 % |
| 14.1 mm | 0.5551 | 73 % |
| 14.2 mm | 0.5591 | 69 % |

## M16 thread data

- Thread: M16 × 2 (coarse)
- Pitch: 2 mm
- Tap drill: 14 mm (0.5512 in)
- Thread engagement: 77 %
- Clearance hole (ISO 273): 17 close, 17.5 normal, 18.5 loose (mm)

## Method

Thread % = 76.98 × (D − drill) / P = 76.98 × 2 / 2 = 77 %. Aim for 65–75 % in steel, 75–85 % in aluminium, brass and plastics.

## FAQ

**What size drill for an M16 × 2 tap?**
Use a 14 mm drill. It leaves about 77 % thread engagement.

**What is 14 mm in inches?**
14 mm is 0.5512 inch.

**What size clearance hole for M16?**
ISO 273 gives 17 mm for a close fit, 17.5 mm normal and 18.5 mm loose.

**How tight should an M16 bolt be?**
About 218 N·m for class 8.8 with dry threads.

Source page: https://machinistcharts.com/tap-drill/m16/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)