# M27 tap drill size

The tap drill for an M27 × 3 metric coarse thread is 24 mm (0.9449 in). It leaves about 77 % thread, the normal range for steel.

## Drill options for M27 × 3

| Drill | Inch | Thread % |
|---|---|---|
| 23.8 mm | 0.9370 | 82 % |
| 23.9 mm | 0.9409 | 80 % |
| 24 mm | 0.9449 | 77 % |
| 24.1 mm | 0.9488 | 74 % |
| 24.2 mm | 0.9528 | 72 % |

## M27 thread data

- Thread: M27 × 3 (coarse)
- Pitch: 3 mm
- Tap drill: 24 mm (0.9449 in)
- Thread engagement: 77 %
- Clearance hole (ISO 273): 28 close, 30 normal, 32 loose (mm)

## Method

Thread % = 76.98 × (D − drill) / P = 76.98 × 3 / 3 = 77 %. Aim for 65–75 % in steel, 75–85 % in aluminium, brass and plastics.

## FAQ

**What size drill for an M27 × 3 tap?**
Use a 24 mm drill. It leaves about 77 % thread engagement.

**What is 24 mm in inches?**
24 mm is 0.9449 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/m27/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)