# M27x2 tap drill size

The tap drill for an M27 × 2 metric fine thread is 25 mm (0.9843 in). It leaves about 77 % thread, the normal range for steel.

## Drill options for M27 × 2

| Drill | Inch | Thread % |
|---|---|---|
| 24.8 mm | 0.9764 | 85 % |
| 24.9 mm | 0.9803 | 81 % |
| 25 mm | 0.9843 | 77 % |
| 25.1 mm | 0.9882 | 73 % |
| 25.2 mm | 0.9921 | 69 % |

## M27x2 thread data

- Thread: M27 × 2 (fine)
- Pitch: 2 mm
- Tap drill: 25 mm (0.9843 in)
- Thread engagement: 77 %
- Clearance hole (ISO 273): 28 close, 30 normal, 32 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 M27 × 2 tap?**
Use a 25 mm drill. It leaves about 77 % thread engagement.

**What is 25 mm in inches?**
25 mm is 0.9843 inch.

**What size clearance hole for M27?**
ISO 273 gives 28 mm for a close fit, 30 mm normal and 32 mm loose.

**How tight should an M27 bolt be?**
About 1,116 N·m for class 8.8 with dry threads.

Source page: https://machinistcharts.com/tap-drill/m27x2/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)