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Quick answer: the two standards call out the same dimensions for the fully threaded hexagon head screw — pitch, s (across flats), k (head height), e (across corners) and thread length. ISO 4017:2022 is the current standard; DIN 933 is the legacy German designation and has been superseded by DIN EN ISO 4017. For new drawings specify ISO 4017; for replacement parts DIN 933 is dimensionally interchangeable, but confirm the tolerance grade (DIN 933 product grade C vs ISO 4017 grade A/B).
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1. Dimensions at a glance
Key sizes — DIN 933 and ISO 4017 (identical values, ISO 4017 grade A shown)| Size | Pitch (mm) | s — across flats (mm) | k — head height (mm) | e — across corners (mm) |
|---|
| M6 | 1.0 | 10 | 4 | 11.05 |
| M8 | 1.25 | 13 | 5.3 | 14.38 |
| M10 | 1.5 | 16 | 6.4 | 17.77 |
| M12 | 1.75 | 18 | 7.5 | 20.03 |
| M16 | 2.0 | 24 | 10 | 26.75 |
| M20 | 2.5 | 30 | 12.5 | 33.53 |
Full tables for all sizes: ISO 4017 M1.6–M64 and DIN 933 M3–M64 on their standard pages.
2. What actually differs
- Standard status. DIN 933:1987 has been superseded by DIN EN ISO 4017; the current international edition is ISO 4017:2022. The old DIN number still appears on legacy drawings and in ERP part descriptions.
- Product grade / tolerance. DIN 933 specifies product grade C; ISO 4017 uses product grade A for the smaller diameters (up to M24) and product grade B for the larger ones. Product grade is a tolerance class, not a strength class — a grade C part is not weaker, just looser on some dimensions.
- Head dimensions. s, k, e and dw follow the same tables; the M10/M12/M14/M22 across-flats differences that affect DIN 931 vs ISO 4014 do not apply to the fully threaded DIN 933 / ISO 4017 pair — the two are dimensionally equivalent.
- Property classes and materials. Both are ordered with ISO 898-1 classes (commonly 8.8, 10.9, 12.9) or stainless A2/A4; the drawing or purchase order must still state the class and finish.
- Thread length. Both products are fully threaded, so there is no partial-thread b value to compare. Bolt length L is measured from the underside of the head to the end of the bolt.
- Marking and documents. Property-class marking and the inspection certificate (EN 10204 3.1 / MTC) are called out separately on the order; the standard number alone does not define the documentation level.
3. Which standard should I specify?
New drawings: ISO 4017:2022. Legacy drawings / aftermarket: DIN 933 is dimensionally interchangeable when product grade C is acceptable; if the drawing calls for tighter tolerances, use ISO 4017 grade A. For M10, M12, M14 and M22 partial-thread bolts the DIN 931 vs ISO 4014 across-flats difference is a separate case — see the DIN 931 page.
4. Substitution checklist
- Read the drawing: does it call DIN 933, ISO 4017, or only the dimensions?
- Confirm the tolerance: if the drawing is DIN 933 grade C, ISO 4017 grade A/B parts are tighter — usually acceptable, but check fit and cost.
- Confirm property class (8.8 / 10.9 / 12.9 / A2-70 / A4-70) and surface finish.
- Confirm marking and documentation requirements (property-class marking, MTC / EN 10204 3.1).
- For export or OEM drawings, update the callout to ISO 4017:2022 and keep DIN 933 as a note only if the customer wants it.
5. Frequently asked questions
Is DIN 933 the same as ISO 4017?
Dimensionally yes for the fully threaded hexagon head screw: the tables for pitch, s, k, e and thread length match. DIN 933 has been superseded by DIN EN ISO 4017; for new drawings use ISO 4017:2022.
Can I substitute DIN 933 for ISO 4017?
Usually yes, because the dimensions match. Check the product grade (DIN 933 grade C vs ISO 4017 grade A/B), the property class, the finish and the marking/documentation requirements before releasing the substitution.
Which product grade does ISO 4017 use?
ISO 4017 uses product grade A up to M24 and product grade B for larger sizes (M16–M64). Product grade is a dimensional tolerance class, not a strength class.
Is DIN 933 weaker than ISO 4017?
No. Product grade C is a looser dimensional tolerance, not a lower strength class. Strength comes from the property class (8.8, 10.9, 12.9, etc.), which is specified separately on both standards.
Does the M10 across-flats difference apply to DIN 933?
No. The s differences at M10, M12, M14 and M22 are between DIN 931 and ISO 4014 (partial-thread bolts). DIN 933 and ISO 4017 share the same across-flats values.
Data compiled by Longze QA from the published standard tables; last verified 2026-11-06. Informational only — the drawing and the purchase order govern the delivered part.