# M33 tap drill size

The tap drill for an M33 × 3.5 metric coarse thread is 29.5 mm (1.1614 in). It leaves about 77 % thread, the normal range for steel.

## Drill options for M33 × 3.5

| Drill | Inch | Thread % |
|---|---|---|
| 29.3 mm | 1.1535 | 81 % |
| 29.4 mm | 1.1575 | 79 % |
| 29.5 mm | 1.1614 | 77 % |
| 29.6 mm | 1.1654 | 75 % |
| 29.7 mm | 1.1693 | 73 % |

## M33 thread data

- Thread: M33 × 3.5 (coarse)
- Pitch: 3.5 mm
- Tap drill: 29.5 mm (1.1614 in)
- Thread engagement: 77 %
- Clearance hole (ISO 273): 34 close, 36 normal, 38 loose (mm)

## Method

Thread % = 76.98 × (D − drill) / P = 76.98 × 3.5 / 3.5 = 77 %. Aim for 65–75 % in steel, 75–85 % in aluminium, brass and plastics.

## FAQ

**What size drill for an M33 × 3.5 tap?**
Use a 29.5 mm drill. It leaves about 77 % thread engagement.

**What is 29.5 mm in inches?**
29.5 mm is 1.1614 inch.

**What size clearance hole for M33?**
ISO 273 gives 34 mm for a close fit, 36 mm normal and 38 mm loose.

**How tight should an M33 bolt be?**
About 2,060 N·m for class 8.8 with dry threads.

Source page: https://machinistcharts.com/tap-drill/m33/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)