A spring washer relies on friction and is pressed flat once the bolt is tightened, so it does little to stop vibration loosening. A Nord-Lock washer pair locks with wedge action, so the bolt cannot turn loose even when the joint vibrates.
How a spring washer is meant to work
A spring washer (also called a split lock washer) is a ring cut through and twisted. The idea is that its spring force keeps some tension in the joint, and its sharp ends dig into the nut and the surface to stop rotation.
Why it struggles in a real joint
In a properly tightened joint, the clamping force is many times higher than the spring force of the washer. The washer is pressed completely flat and from then on behaves much like a plain washer.
- No spring left: once flat, it adds almost no extra tension.
- Little bite: the ends do not reliably dig into hardened nuts or surfaces.
- Same weakness as plain washers: when the joint slips sideways under vibration, friction drops and the nut can still turn back.
Vibration tests on the Junker machine show joints with spring washers losing preload in much the same way as joints with plain washers. Several German standards for spring washers, including DIN 127, have been withdrawn without replacement.
How a Nord-Lock washer works
A Nord-Lock washer comes as a pair. Each washer has cams on the inside and teeth on the outside. The teeth grip the bolt head and the joint surface, so the only movement possible is between the two cam faces.
The cams are steeper than the thread. If the bolt tries to turn loose, the cams ride up and stretch the bolt further, which stops the turning. The joint is locked by bolt tension, not by friction.
Side by side
| Spring washer | Nord-Lock washer pair | |
|---|---|---|
| How it locks | Friction and spring force | Wedge action using bolt tension |
| Sideways vibration | Little resistance once pressed flat | Stops the bolt turning loose |
| Lubricated bolts | Friction drops, so does locking | Locking not affected |
| High-strength bolts | Spring force is tiny compared with preload | Designed for bolts up to property class 12.9 |
| Reuse | Usually replaced after removal | Reusable in most cases |
| Part price | Very low | Higher per part |
When is a spring washer good enough?
In low-load, non-critical joints, where a loose bolt would be harmless and easy to spot, a spring washer may be acceptable. For any joint that vibrates and matters, such as machines, vehicles, structures and power equipment, use a positive locking method.
Switching from spring washers to Nord-Lock
- Replace each spring washer with one Nord-Lock pair, fitted as supplied.
- Match the washer material to the bolt: steel with steel, stainless with stainless.
- Check the tightening torque, because friction under the head changes. We can help with the values.
Not sure which part you need? Read how to choose the right Nord-Lock washer, or see the Original washer range.