# DIN 7991 — DIN / ISO / BS fastener equivalents and the sizes where they are not interchangeable

For DIN 7991, iso standard is ISO 10642; part is Flat Head Socket Cap; interchangeability verdict is Check spec, verified against its source on 2026-08-05.

- **DIN standard:** DIN 7991 _(verified: appears in the quote below)_
- **ISO standard:** ISO 10642 _(verified: appears in the quote below)_
- **Part:** Flat Head Socket Cap _(verified: appears in the quote below)_
- **Interchangeability verdict:** Check spec _(verified: appears in the quote below)_
- **BS standard:** BS4168 _(per trfastenings.com, not stated by the source above)_

## What the source says

> Flat Head Socket Cap | DIN 7991 | ISO 10642 | Check spec | Head angle/height differences exist.

## Sources disagree

More than one authority states this, and they do not state the same
thing. Both are reproduced with the source each came from.

### Part

monsterbolts.com says part is **Flat Head Socket Cap**, as of 2026-08-05.

> Flat Head Socket Cap | DIN 7991 | ISO 10642 | Check spec | Head angle/height differences exist.

Source: https://monsterbolts.com/pages/common-din-numbers-for-metric-fasteners

trfastenings.com says part is **Hexagon Socket Countersunk Head Cap Screws**, as of 2026-08-05.

> DIN 7991 | ISO 10642 | BS4168 | Hexagon Socket Countersunk Head Cap Screws |

Source: https://www.trfastenings.com/knowledge-base/engineering-data/fastener-standards


## Source

- https://monsterbolts.com/pages/common-din-numbers-for-metric-fasteners
- https://www.trfastenings.com/knowledge-base/engineering-data/fastener-standards

Last verified: 2026-08-05. Review by: 2029-08-04.
Part of [DIN / ISO / BS fastener equivalents and the sizes where they are not interchangeable](https://referencesource.org/fastener-standard-interchangeability-exceptions/).