# DIN 551 — DIN / ISO / BS fastener equivalents and the sizes where they are not interchangeable

For DIN 551, iso standard is ISO 4766; part is Slotted Set Screw – Flat; interchangeability verdict is Check spec, verified against its source on 2026-08-05.

- **DIN standard:** DIN 551 _(verified: appears in the quote below)_
- **ISO standard:** ISO 4766 _(verified: appears in the quote below)_
- **Part:** Slotted Set Screw – Flat _(verified: appears in the quote below)_
- **Interchangeability verdict:** Check spec _(verified: appears in the quote below)_

## What the source says

> Slotted Set Screw – Flat | DIN 551 | ISO 4766 | Check spec | Slot width/tolerance differences.

## 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 **Slotted Set Screw – Flat**, as of 2026-08-05.

> Slotted Set Screw – Flat | DIN 551 | ISO 4766 | Check spec | Slot width/tolerance differences.

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

trfastenings.com says part is **Slotted Set Screws with flat point**, as of 2026-08-05.

> DIN 551 | ISO 4766 | | Slotted Set Screws with flat point |

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/).