DIN 963 M8 × 20 Countersunk head (90°)
DIN 963 M8 × 20 is a countersunk head screw with a 20 mm nominal length, on a M8 × 1 mm metric thread. Slotted flat head screw for a flush finish. Note that countersunk heads pull the joint sideways, so they should not be used to locate parts.
Dimensions
- Standard
- DIN 963
- Type
- Countersunk head screw
- Size
- M8 × 20
- Thread
- M8 × 1
- Length L
- 20 mm
- Head diameter dk
- 14.5 mm
- Head height k
- 4 mm
- Drive
- Slotted
- Head
- Countersunk head (90°)
Nominal values in millimetres as published in DIN 963. Estimated weight 11.1 g per piece in steel (11.17 g in stainless), calculated from the nominal geometry — real parts vary with tolerance and head chamfers.
Thread data
Full M8 thread pageOther lengthsDIN 963 M8
All M8 specificationsInterchangeability
DIN 963 is catalogued with ISO 2009 as its equivalent designation. Dimensions are compared field by field rather than assumed identical.
Choosing and fitting this size
DIN 963 M8 × 20 is a countersunk head (90°) in M8, 20 mm long under the head, on a 1 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, M8 × 1 mm takes a 7 mm tap drill, and the external thread's minor diameter is 6.77 mm — that is the section carrying the load, not the nominal M8 figure. Thread engagement of at least one times the nominal diameter is what lets the bolt fail before the thread strips.