DIN 439 M20 Hexagon thin nut
DIN 439 M20 is a hexagon thin nut, on a M20 × 1.5 mm metric thread. A low profile hex nut used as a lock nut against a full nut, or where axial space is tight. Because it carries fewer threads it is not rated for full service load on its own.
Dimensions
- Standard
- DIN 439
- Type
- Hexagon thin nut
- Size
- M20
- Thread
- M20 × 1.5
- Socket size s
- 30 mm
- Height m
- 10 mm
- Drive
- External hexagon
Nominal values in millimetres as published in DIN 439. Estimated weight 21.226 g per piece in steel (21.361 g in stainless), calculated from the nominal geometry — real parts vary with tolerance and head chamfers.
Thread data
Full M20 thread pageOther lengthsDIN 439 M20
All M20 specificationsInterchangeability
DIN 439 is catalogued with ISO 4035 as its equivalent designation. Dimensions are compared field by field rather than assumed identical.
Choosing and fitting this size
DIN 439 M20 is a M20 nut, on a 1.5 mm coarse pitch. Mating threads should be a matching class nut in the same property class.
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, M20 × 1.5 mm takes a 18.5 mm tap drill, and the external thread's minor diameter is 18.16 mm — that is the section carrying the load, not the nominal M20 figure. Thread engagement of at least one times the nominal diameter is what lets the bolt fail before the thread strips.