ISO 4017 dimensions
Hexagon head screws, fully threaded — the ISO standard that replaced DIN 933.
The ISO standard. DIN 933 is the DIN number for the same part.
What ISO 4017 is
ISO 4017 covers the same fastener as DIN 933 and supersedes it. The threads are identical and the two are interchangeable in the hole. The heads are not identical at every size, which is the source of the missing-socket problem below.
Threaded all the way to the head
The thread on a ISO 4017 runs the entire length, right up under the head. That is the whole distinction between this standard and ISO 4014, which leaves a plain unthreaded shank under the head, and it decides which one a joint wants.
Full thread is the right choice when the bolt is clamping — pulling two faces together and holding them by friction. Thread engagement is available at any grip length, so one length covers a range of stack-ups, and a ISO 4017 bolt that is slightly too long still works because the nut simply runs further down. That flexibility is why a workshop stocks these and reaches for them first.
It is the wrong choice when the joint is loaded across the bolt rather than along it. A thread in shear is being cut at the root, where the section is smallest and the notch is sharpest: an M10 ISO 4017 presents roughly 8.5 mm of metal to a shear load — the thread root sits near the diameter the hole was drilled to — where the plain shank of a ISO 4014 presents the full 10 mm. That is on the order of 38% more area, in the place where it matters.
ISO 4017 dimensions, M2 to M24
| Size | Pitch | Across flats | Across corners | Clearance hole |
|---|---|---|---|---|
| M2 | 0.4 mm | 4 mm | 4.62 mm | 2.4 mm |
| M2.5 | 0.45 mm | 5 mm | 5.77 mm | 2.9 mm |
| M3 | 0.5 mm | 5.5 mm | 6.35 mm | 3.4 mm |
| M4 | 0.7 mm | 7 mm | 8.08 mm | 4.5 mm |
| M5 | 0.8 mm | 8 mm | 9.24 mm | 5.5 mm |
| M6 | 1 mm | 10 mm | 11.55 mm | 6.6 mm |
| M8 | 1.25 mm | 13 mm | 15.01 mm | 9 mm |
| M10 | 1.5 mm | 16 mm (DIN 17) | 18.48 mm | 11 mm |
| M12 | 1.75 mm | 18 mm (DIN 19) | 20.78 mm | 13.5 mm |
| M14 | 2 mm | 21 mm (DIN 22) | 24.25 mm | 15.5 mm |
| M16 | 2 mm | 24 mm | 27.71 mm | 17.5 mm |
| M20 | 2.5 mm | 30 mm | 34.64 mm | 22 mm |
| M24 | 3 mm | 36 mm | 41.57 mm | 26 mm |
Across corners is the across-flats divided by cos 30°, which is what a socket has to clear. The standards quote a slightly smaller minimum because the corners may be rounded.
ISO 4017 against DIN 933
The threads are identical and the two are fully interchangeable in the hole. The heads are not identical. At M10, M12, M14 — DIN specifies 17 mm, 19 mm, 22 mm across the flats where ISO specifies 16, 18, 21 mm. Everywhere else in this range the two agree exactly.
That difference is small and extremely annoying. An M10 bolt made to ISO 4017 takes a 16 mm spanner and one made to DIN 933 takes 17 mm. Both are M10, both thread into the same hole, and a socket set built for one will skip a size on the other. It is why metric sets sold today usually carry both 16 and 17.
Frequently asked questions
What is ISO 4017?
Hexagon head screws, fully threaded — the ISO standard that replaced DIN 933. It is the ISO standard covering the same fastener as DIN 933.
Is ISO 4017 the same as DIN 933?
The threads are the same and the two are interchangeable in the hole, but the heads differ at M10, M12, M14. M10, M12, M14 — DIN specifies 17 mm, 19 mm, 22 mm across the flats where ISO specifies 16, 18, 21 mm. Everywhere else the two agree.
What spanner does an M10 ISO 4017 take?
16 mm. ISO specifies that size across the flats; the other standard specifies 17 mm for the same M10 thread. This is why a socket set that covers 8, 10, 13, 17 and 19 occasionally meets a bolt it cannot grip.
Is ISO 4017 still current?
Yes. ISO 4017 is the current international standard; DIN 933 is the withdrawn German one that preceded it. Suppliers still sell and label parts by the DIN number because that is what customers ask for.
Other fastener standards
- DIN 931 — Hexagon head bolts, partially threaded — a plain shank under the head
- ISO 4014 — Hexagon head bolts, partially threaded — the ISO standard that replaced DIN 931
- DIN 912 — Hexagon socket head cap screws — the cylindrical head driven by a hex key
- ISO 4762 — Hexagon socket head cap screws — the ISO standard matching DIN 912
- DIN 934 — Hexagon nuts — the plain hex nut
Every fastener standard here · Metric thread sizes · Tap drill sizes · Spanner sizes