---
title: "M33×3.5 tap drill 29.5 mm, clearance 34 mm"
description: "M33×3.5: tap drill 29.5 mm, clearance hole 34 mm, 50 mm hex. Full thread dimensions, how to identify it, and torque."
url: https://atoneplace.net/fastener/m33-3-5/
site: "At One Place"
---

# M33×3.5 thread

**M33×3.5 tap drill: 29.5 mm**

Clearance hole 34 mm · 50 mm hex

M33×3.5 is a coarse metric thread with a 33 mm (1.299") major diameter and 3.5 mm pitch. Tap it with a 29.5 mm drill; drill 34 mm to pass a bolt through.

## The numbers

- **Designation:** M33×3.5
- **Major diameter:** 33 mm / 1.299"
- **Minor diameter:** 29.211 mm
- **Pitch:** 3.5 mm pitch
- **Tap drill (75% thread):** 29.5 mm — 29.5 mm
- **Clearance hole (close fit):** 34 mm / 1.339"
- **Hex across flats:** 50 mm

## How to measure what you have

1. Measure across the thread crests with calipers. A used M33×3.5 reads a little under 33 mm — the crests are truncated by the standard, then worn and plated, so anything from about 32.6 mm up is consistent with this size.
2. Measure the pitch: put a rule against the threads and count the distance over ten crests, then divide by ten. This one should give 3.5 mm.
3. A thread pitch gauge settles it in seconds and costs very little. Guessing between a coarse and a fine thread of the same diameter is the usual way a thread gets stripped.

## Tightening torque

**Typical torque: 1700–2250 N·m**

1254.1–1659.8 lb·ft

> Plain steel property class 8.8 or SAE grade 5, dry threads, tightened to about 65% of yield. Lubricated threads reach the same preload at 20-30% less torque. Where the manufacturer publishes a figure — spark plugs, wheel nuts, cylinder heads — use theirs.

## Where this size turns up

- Heavy flange bolting
- Large press and forging equipment
- Marine and offshore structural connections

## Common questions

### What size drill for an M33×3.5 tap?

29.5 mm (29.5 mm), which gives about 75% thread engagement.

### What clearance hole for M33×3.5?

34 mm for a close fit — enough to pass the bolt without slop.

### What spanner fits M33×3.5?

50 mm across the flats on a standard hex head.

## Related pages

- [M30×3.5](https://atoneplace.net/fastener/m30-3-5/)
- [M36×4](https://atoneplace.net/fastener/m36-4/)
- [M30×2](https://atoneplace.net/fastener/m30-2/)
- [M27×3](https://atoneplace.net/fastener/m27-3/)
- [M27×2](https://atoneplace.net/fastener/m27-2/)
- [M24×3](https://atoneplace.net/fastener/m24-3/)
- [M42×4.5](https://atoneplace.net/fastener/m42-4-5/)
- [M24×2](https://atoneplace.net/fastener/m24-2/)
- [M24×1.5](https://atoneplace.net/fastener/m24-1-5/)
- [M22×2.5](https://atoneplace.net/fastener/m22-2-5/)

## Sources

- Official vendor product documentation — At One Place (/about/)
- Typical range compiled from manufacturer specifications — At One Place (/about/)