---
title: "M24×3 tap drill 21 mm, clearance 25 mm"
description: "M24×3: tap drill 21 mm, clearance hole 25 mm, 36 mm hex. Full thread dimensions, how to identify it, and torque."
url: https://atoneplace.net/fastener/m24-3/
site: "At One Place"
---

# M24×3 thread

**M24×3 tap drill: 21 mm**

Clearance hole 25 mm · 36 mm hex

M24×3 is a coarse metric thread with a 24 mm (0.945") major diameter and 3 mm pitch. Tap it with a 21 mm drill; drill 25 mm to pass a bolt through.

## The numbers

- **Designation:** M24×3
- **Major diameter:** 24 mm / 0.945"
- **Minor diameter:** 20.752 mm
- **Pitch:** 3 mm pitch
- **Tap drill (75% thread):** 21 mm — 21 mm
- **Clearance hole (close fit):** 25 mm / 0.984"
- **Hex across flats:** 36 mm

## How to measure what you have

1. Measure across the thread crests with calipers. A used M24×3 reads a little under 24 mm — the crests are truncated by the standard, then worn and plated, so anything from about 23.6 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 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: 620–840 N·m**

457.4–619.7 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

- Structural steel column splices
- Wind turbine and tower flange bolting
- Large pressure-vessel and pipe flanges

## Other threads at this diameter

*Same diameter, different pitch. Forcing the wrong one strips the thread in a turn or two.*

| Thread | Pitch | Tap drill | Clearance |
| --- | --- | --- | --- |
| M24×2 | 2 mm | 22 mm | 25 mm |
| M24×1.5 | 1.5 mm | 22.5 mm | 25 mm |

## Common questions

### What size drill for an M24×3 tap?

21 mm (21 mm), which gives about 75% thread engagement.

### What clearance hole for M24×3?

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

### What spanner fits M24×3?

36 mm across the flats on a standard hex head.

## Related pages

- [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/)
- [M22×1.5](https://atoneplace.net/fastener/m22-1-5/)
- [M27×3](https://atoneplace.net/fastener/m27-3/)
- [M27×2](https://atoneplace.net/fastener/m27-2/)
- [M20×2.5](https://atoneplace.net/fastener/m20-2-5/)
- [M20×1.5](https://atoneplace.net/fastener/m20-1-5/)
- [M20×2](https://atoneplace.net/fastener/m20-2/)
- [M18×2.5](https://atoneplace.net/fastener/m18-2-5/)
- [M30×3.5](https://atoneplace.net/fastener/m30-3-5/)
- [M18×1.5](https://atoneplace.net/fastener/m18-1-5/)

## Sources

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