DIN 127 M4 Spring lock washer
DIN 127 M4 is a spring lock washer, sized for M4 bolts. A split helical spring washer intended to resist loosening. Worth knowing that independent testing has repeatedly found its locking effect is marginal once the joint is properly preloaded — for safety critical joints use a prevailing torque nut instead.
Dimensions
- Standard
- DIN 127
- Type
- Spring lock washer
- Size
- M4
- For bolt size
- M4
- Socket size s
- 0.9 mm
- Total height h
- 1.8 mm
- Inside diameter d1
- 4.1 mm
Nominal values in millimetres as published in DIN 127.
Other lengthsDIN 127 M4
All M4 specificationsChoosing and fitting this size
DIN 127 M4 is a washer with a 4.1 mm inside diameter. It sits under a bolt head or nut to spread the clamping load; the inside diameter matches the bolt it is specified for, so the washer and fastener should always be ordered as a pair.
Hardness is the governing property rather than tensile strength: a 200 HV washer suits bolts up to class 10.9, while 140 HV washers are intended for class 8.8 and below. Using a soft washer under a high-grade bolt lets the washer deform before the bolt reaches its preload, which quietly loses clamping force.