# DIN 7991 · M20 · dk max. — Sizes where a DIN fastener and its ISO equivalent are not interchangeable

For DIN 7991, size is M20; dimension that differs is dk max; iso standard is ISO 10642; din value is 36; iso value is 40.32, verified against its source on 2026-10-12.

- **DIN standard:** DIN 7991 _(verified: appears in the quote below)_
- **ISO standard:** ISO 10642 _(verified: appears in the quote below)_
- **Size:** M20 _(verified: appears in the quote below)_
- **Dimension that differs:** dk max. _(verified: appears in the quote below)_
- **DIN value:** 36 _(verified: appears in the quote below)_
- **ISO value:** 40.32 _(verified: appears in the quote below)_

## What the source says

**ISO standard, DIN value and ISO value:** The source prints these values inside the passage below but does not name them there. The passage shows where each one appears; what ties them to this record is the position on the page, not anything the passage says.

> Thread M10 M12 M14 M16 M18 M20 M22 M24 ISO 10642 22.4 26.88 30.8 33.6 – 40.32 – – dk max. DIN 7991 20 24 27 30 33 36 36 39

## Source

- https://www.wurthindustry.ca/media/downloads/wic_pdfs/Fasteners_DIN-EN-ISO_Standards.pdf

Last verified: 2026-10-12. Review by: 2029-10-11.
Part of [Sizes where a DIN fastener and its ISO equivalent are not interchangeable](https://referencesource.org/fastener-standard-interchangeability-exceptions/).