DIN 661 8 × 20 Countersunk head (75°)
DIN 661 8 × 20 is a countersunk head rivet with a 20 mm nominal length, 8 mm shank diameter. A solid rivet with a 75° countersunk head that finishes flush with the surface. Same shank and same hole as DIN 660 — only the head differs, and the head is where the two tables part company: the countersunk head is 0.1 mm wider at 1.4 mm and at 3.5 mm nominal, and its depth k is one step smaller than the round head's height at every size. That difference is the whole reason a countersunk rivet cannot be substituted where a round head was specified, and vice versa: the head is what carries the load into the sheet.
Dimensions
- Standard
- DIN 661
- Type
- Countersunk head rivet
- Size
- 8 × 20
- Diameter
- 8
- Length L
- 20 mm
- Head diameter d2
- 14 mm
- Shank diameter d3 min.
- 7.76 mm
- Head depth k
- 4 mm
- Hole diameter dH12
- 8.4 mm
- Head
- Countersunk head (75°)
Nominal values in millimetres as published in DIN 661. Estimated weight 9.371 g per piece in steel (9.431 g in stainless), calculated from the nominal geometry — real parts vary with tolerance and head chamfers.
Other lengthsDIN 661 8
All 8 specificationsChoosing and fitting this size
DIN 661 8 × 20 is a countersunk head (75°) with a 8 mm shank, 20 mm long overall, measured from the top face of the head. The hole is drilled 8.4 mm — slightly larger than the shank, so the rivet drops in without force. Setting upsets the protruding end into a second head, which makes the joint permanent: there is no way to take it apart without destroying the rivet.
Rivets carry no property class. The standard sets a minimum tensile strength per material group instead of a single grade, and the material is part of the designation — St for steel, A2 or A4 for stainless — so the strength of a rivet is a property of the wire it was made from rather than of a marking on the head. Cold setting work-hardens the shank as it upsets, which is why a properly set joint is stronger than the annealed rivet that went into it; it also means the rivet cannot be straightened and re-used after a bad set.