DIN 933 M18 × 40 Hexagon head
DIN 933 M18 × 40 is a hexagon head bolt with a 40 mm nominal length, on a M18 × 1.5 mm metric thread. A hexagon head fastener threaded all the way to the head. Glyph marking on the head identifies the property class, normally 8.8, 10.9 or A2-70.
Dimensions
- Standard
- DIN 933
- Type
- Hexagon head bolt
- Size
- M18 × 40
- Thread
- M18 × 1.5
- Length L
- 40 mm
- Socket size s
- 27 mm
- Head height k
- 11.5 mm
- Drive
- External hexagon
- Head
- Hexagon head
Nominal values in millimetres as published in DIN 933. Estimated weight 79.903 g per piece in steel (80.412 g in stainless), calculated from the nominal geometry — real parts vary with tolerance and head chamfers.
Thread data
Full M18 thread pageOther lengthsDIN 933 M18
All M18 specificationsInterchangeability
DIN 933 is catalogued with ISO 4017 as its equivalent designation. Dimensions are compared field by field rather than assumed identical.
Choosing and fitting this size
DIN 933 M18 × 40 is a hexagon head in M18, 40 mm long under the head, on a 1.5 mm coarse pitch. Mating threads should be a matching class nut or a tapped hole of the same nominal size.
Common stock grades are 8.8, 10.9 and 12.9 in steel, plus A2-70 and A4-80 in stainless. Class 10.9 and 12.9 carry roughly 1.25 and 1.5 times the proof load of 8.8, but they also need a properly rated mating nut — a class 8 nut under a 12.9 bolt simply moves the failure into the thread. Zinc-plated 10.9 and above should be baked to avoid hydrogen embrittlement.
For a tapped hole, M18 × 1.5 mm takes a 16.5 mm tap drill, and the external thread's minor diameter is 16.16 mm — that is the section carrying the load, not the nominal M18 figure. Thread engagement of at least one times the nominal diameter is what lets the bolt fail before the thread strips.