---
title: "M30×3.5 tap drill 26.5 mm, clearance 31 mm"
description: "M30×3.5: tap drill 26.5 mm, clearance hole 31 mm, 46 mm hex. Full thread dimensions, how to identify it, and torque."
url: https://atoneplace.net/fastener/m30-3-5/
site: "At One Place"
---

# M30×3.5 thread

**M30×3.5 tap drill: 26.5 mm**

Clearance hole 31 mm · 46 mm hex

M30×3.5 is a coarse metric thread with a 30 mm (1.181") major diameter and 3.5 mm pitch. Tap it with a 26.5 mm drill; drill 31 mm to pass a bolt through.

## The numbers

- **Designation:** M30×3.5
- **Major diameter:** 30 mm / 1.181"
- **Minor diameter:** 26.211 mm
- **Pitch:** 3.5 mm pitch
- **Tap drill (75% thread):** 26.5 mm — 26.5 mm
- **Clearance hole (close fit):** 31 mm / 1.220"
- **Hex across flats:** 46 mm

## How to measure what you have

1. Measure across the thread crests with calipers. A used M30×3.5 reads a little under 30 mm — the crests are truncated by the standard, then worn and plated, so anything from about 29.6 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: 1250–1650 N·m**

922.1–1217.2 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

- Wind turbine tower and foundation flanges
- Large machine holding-down bolts
- Heavy structural anchor bolts

## 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 |
| --- | --- | --- | --- |
| M30×2 | 2 mm | 28 mm | 31 mm |

## Common questions

### What size drill for an M30×3.5 tap?

26.5 mm (26.5 mm), which gives about 75% thread engagement.

### What clearance hole for M30×3.5?

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

### What spanner fits M30×3.5?

46 mm across the flats on a standard hex head.

## Related pages

- [M30×2](https://atoneplace.net/fastener/m30-2/)
- [M27×3](https://atoneplace.net/fastener/m27-3/)
- [M33×3.5](https://atoneplace.net/fastener/m33-3-5/)
- [M27×2](https://atoneplace.net/fastener/m27-2/)
- [M24×3](https://atoneplace.net/fastener/m24-3/)
- [M36×4](https://atoneplace.net/fastener/m36-4/)
- [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/)
- [M20×2.5](https://atoneplace.net/fastener/m20-2-5/)

## Sources

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