# 558 — Fastener standard equivalences: DIN to ISO / EN crossover

For 558, fastener description is Hexagon screws, Thread Approximately to Head, Metric Thread, Type g; iso equivalent is 4018; interchangeability is Nominal size extended; width across flats according to DIN ISO 272 included; modification notes is Nominal size extended; width across flats according to DIN ISO 272 included, verified against its source on 2026-08-12.

- **DIN standard:** 558 _(verified: appears in the quote below)_
- **Fastener description:** Hexagon screws, Thread Approximately to Head, Metric Thread, Type g _(verified: appears in the quote below)_
- **ISO equivalent:** 4018 _(verified: appears in the quote below)_
- **Interchangeability:** Nominal size extended; width across flats according to DIN ISO 272 included _(verified: appears in the quote below)_
- **Modification notes:** Nominal size extended; width across flats according to DIN ISO 272 included _(verified: appears in the quote below)_

## What the source says

> Hexagon screws, Thread Approximately to Head, Metric Thread, Type g | 558 | 4018 | 24018 | 4018 | 4018 | 2001-03 | Hexagon head screws – Product grade C | Nominal size extended; width across flats according to DIN ISO 272 included |

## 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.

### Fastener description

fullerfasteners.com says fastener description is **Hexagon screws, Thread Approximately to Head, Metric Thread, Type g**, as of 2026-08-12.

> Hexagon screws, Thread Approximately to Head, Metric Thread, Type g | 558 | 4018 | 24018 | 4018 | 4018 | 2001-03 | Hexagon head screws – Product grade C | Nominal size extended; width across flats according to DIN ISO 272 included |

Source: https://fullerfasteners.com/tech/din-iso-en-crossover-chart/

monsterbolts.com says fastener description is **Alt coarse hex FT.**, as of 2026-08-12.

> DIN 558 | ISO 4018 | Fully interchangeable

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

trfastenings.com says fastener description is **Hexagon Head Screws**, as of 2026-08-12.

> DIN 558 | ISO 4018 | | Hexagon Head Screws |

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


### Interchangeability

fullerfasteners.com says interchangeability is **Nominal size extended; width across flats according to DIN ISO 272 included**, as of 2026-08-12.

> Hexagon screws, Thread Approximately to Head, Metric Thread, Type g | 558 | 4018 | 24018 | 4018 | 4018 | 2001-03 | Hexagon head screws – Product grade C | Nominal size extended; width across flats according to DIN ISO 272 included |

Source: https://fullerfasteners.com/tech/din-iso-en-crossover-chart/

monsterbolts.com says interchangeability is **Fully interchangeable**, as of 2026-08-12.

> DIN 558 | ISO 4018 | Fully interchangeable

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


## Source

- https://fullerfasteners.com/tech/din-iso-en-crossover-chart/
- https://monsterbolts.com/pages/common-din-numbers-for-metric-fasteners
- https://www.trfastenings.com/knowledge-base/engineering-data/fastener-standards

Last verified: 2026-08-12. Review by: 2028-08-11.
Part of [Fastener standard equivalences: DIN to ISO / EN crossover](https://referencesource.org/fastener-thread-standard-equivalence/).