ISO 965-1:2026: fifth edition of the metric thread tolerance standard

ISO 965-1, the tolerance system for ISO general purpose metric screw threads (M), has a fifth edition dated April 2026. It covers threads that conform to ISO 261, with basic and design profiles to ISO 68-1. This is the standard that defines the 6H nut and 6g bolt on almost every metric drawing. It does so through tolerance grades (numbers such as 4, 6 and 8) and tolerance positions (letters such as H, G, h and g).

The Foreword says the fifth edition cancels and replaces ISO 965-1:2013, has been technically revised, and incorporates Amendment ISO 965-1:2013/Amd 1:2021. The main changes it lists are in the table above. The full text is paid. The Foreword, contents and Clauses 1 to 6 are in the public preview linked below, and every statement in this note comes from that preview.

Why it matters for design engineers

The listed changes add clauses rather than rewrite the core tables. The Foreword lists no change to the fundamental deviations or tolerance grade values that most calculations use. A Foreword list is a summary, though, not a complete diff. The Amendment of 2021 is also now part of the base text. Until you have compared the 2026 tables with the ones you use, treat “unchanged” as unverified.

What to check:

If you	Check
Compute thread stripping or engagement from 6H/6g limits	The fundamental deviations (Table 1) and grade 6 tolerances TD1, Td, TD2 and Td2 for your pitch against your source
Specify plated or coated threads	New Clause 10 and the coated-thread designation in 13.5, before relying on a company rule for the allowance
Use non-tabulated pitches	The new paragraphs on special tolerances in Clauses 6 and 7 and Annex A.1
Work out the external thread root area from d3	The new Annex B formulae and the Td3 tolerance
Cite “ISO 965-1” on drawings and reports	Whether your quality system requires a dated edition, and whether suppliers have moved to 2026

Clause 6 of the 2026 text lists the standardised tolerance positions. They are G and H for internal threads and a, b, c, d, e, f, g and h for external threads. For hot dip galvanised threads, it points to ISO 965-4 and ISO 965-5 for the az, AZ and AX positions. The Foreword does not say whether any of these positions are new relative to the 2013 base text plus its amendment, so we make no claim either way.

Our tools

The thread engagement calculator takes its metric 6H/6g limits from ISO 965-1 Tables 1, 3, 4, 5 and 6, typed from the 2013 edition, and cites ISO 965-1:2013. We have not yet compared those rows with the 2026 tables. Until that check is recorded in the calculator’s changelog, the calculator keeps citing the 2013 edition, so the citation matches the data behind it.