---
title: "M42×4.5 tap drill 37.5 mm, clearance 43 mm"
description: "M42×4.5: tap drill 37.5 mm, clearance hole 43 mm, 65 mm hex. Full thread dimensions, how to identify it, and torque."
url: https://atoneplace.net/fastener/m42-4-5/
site: "At One Place"
---

# M42×4.5 thread

**M42×4.5 tap drill: 37.5 mm**

Clearance hole 43 mm · 65 mm hex

M42×4.5 is a coarse metric thread with a 42 mm (1.654") major diameter and 4.5 mm pitch. Tap it with a 37.5 mm drill; drill 43 mm to pass a bolt through.

## The numbers

- **Designation:** M42×4.5
- **Major diameter:** 42 mm / 1.654"
- **Minor diameter:** 37.129 mm
- **Pitch:** 4.5 mm pitch
- **Tap drill (75% thread):** 37.5 mm — 37.5 mm
- **Clearance hole (close fit):** 43 mm / 1.693"
- **Hex across flats:** 65 mm

## How to measure what you have

1. Measure across the thread crests with calipers. A used M42×4.5 reads a little under 42 mm — the crests are truncated by the standard, then worn and plated, so anything from about 41.6 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 4.5 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: 3450–4650 N·m**

2545.1–3430.3 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 flange bolts
- Bridge bearing and expansion-joint anchors
- Heavy press and rolling mill frames

## Common questions

### What size drill for an M42×4.5 tap?

37.5 mm (37.5 mm), which gives about 75% thread engagement.

### What clearance hole for M42×4.5?

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

### What spanner fits M42×4.5?

65 mm across the flats on a standard hex head.

## Related pages

- [M36×4](https://atoneplace.net/fastener/m36-4/)
- [M48×5](https://atoneplace.net/fastener/m48-5/)
- [M33×3.5](https://atoneplace.net/fastener/m33-3-5/)
- [M30×3.5](https://atoneplace.net/fastener/m30-3-5/)
- [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/)
- [M24×2](https://atoneplace.net/fastener/m24-2/)
- [M24×1.5](https://atoneplace.net/fastener/m24-1-5/)

## Sources

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