Both washers exist to solve the same problem: bolts loosening under vibration. But they work on completely different principles - and only one of them holds up in the industry’s toughest vibration test. Here is an honest look at both, including when the cheaper option is still the right call.
How a Spring Lock Washer Works (DIN 127)
A spring lock washer (helical spring washer) is a split ring of spring steel with a helical set. When the bolt is tightened, the washer flattens and acts as a spring between the bolt head and the surface, maintaining tension in the joint. The sharp split edges can also bite lightly into the mating surfaces, adding friction.
- Mechanism: spring preload plus friction
- Standard: DIN 127 (Type A and B), DIN 128
- Size range: M3 - M64
- Material: spring steel; SS 304 / SS 316 for corrosive environments
- Cost: very low - the default anti-loosening measure in general engineering
How a Wedge Lock Washer Works
A wedge lock washer is a matched pair of washers with radial cams on their mating faces and gripping serrations on their outer faces. The critical geometry: the cam angle is greater than the thread pitch angle of the bolt.
When vibration tries to rotate the bolt loose, the serrations keep each washer locked to its surface, so the movement happens between the two cam faces. Because the cams are steeper than the thread, riding up the cam stretches the bolt further - tension increases instead of releasing. The joint physically cannot rotate loose; it can only get tighter.
- Mechanism: positive mechanical wedge action (not friction)
- Supplied: in pre-assembled pairs - never split a pair
- Size range: M5 - M100
- Material: hardened steel or SS 316; zinc-flake or hot-dip galvanised finish
- Temperature: -50 °C to +300 °C
The Junker Test - and Why DIN Withdrew DIN 127
The Junker test (DIN 65151) is the industry’s severest check of a fastener’s vibration resistance: a bolted joint is subjected to transverse (sideways) vibration while a load cell records the clamping force in real time. Joints that rely on friction alone typically lose their preload within seconds.
The uncomfortable fact: after a programme of Junker testing, DIN concluded that helical spring washers do not reliably prevent self-loosening of high-strength bolts under transverse vibration - and withdrew the DIN 127 standard. Spring washers are still made and sold to the old specification, and they remain useful for moderate duty, but they are not a severe-vibration solution.
Wedge lock washers, by contrast, are the type of device that passes Junker testing - because their locking action does not depend on friction in the thread at all.
Side-by-Side Comparison
| Property | Spring Lock (DIN 127) | Wedge Lock (Cam Pair) |
|---|---|---|
| Locking principle | Spring preload + friction | Positive cam geometry |
| Severe vibration (Junker) | Loses preload | Maintains preload |
| Moderate vibration | Adequate | Excellent |
| Supplied as | Single washer | Matched pair |
| Size range | M3 - M64 | M5 - M100 |
| Relative cost | Very low | Significantly higher |
| Typical use | General engineering, enclosures, light machinery | Rail, wind, mining, structural, heavy machinery |
Which One Should You Use?
Be honest about the duty level:
- Choose DIN 127 spring washers for general assemblies, electrical enclosures, machinery bases, and joints with light-to-moderate vibration where periodic inspection is possible. They are cheap, familiar, and adequate for most of industry.
- Choose wedge lock washers when vibration is severe or the joint is safety-critical and inaccessible - rolling stock, wind turbines, crushers and screens, structural connections. The cost difference is trivial compared to the cost of one failed joint.
We stock both: DIN 127 spring lock washers (M3-M64) and cam-type wedge lock washer pairs (M5-M100), ex-stock Mumbai.
Need Anti-Vibration Washers?
DIN 127 spring lock washers and wedge lock washer pairs, stocked ex-Mumbai with same-week dispatch and pan-India delivery.
View Washer RangeFrequently Asked Questions
Do spring lock washers actually prevent bolts from loosening?
Under moderate vibration and static loads, a DIN 127 spring washer helps maintain preload and compensates for minor settling. However, in Junker transverse-vibration testing, spring washers were shown not to prevent self-loosening of high-strength bolted joints - which is why DIN withdrew the DIN 127 standard. For severe, safety-critical vibration, use a positive-locking solution such as wedge lock washers.
Why was DIN 127 withdrawn as a standard?
After a programme of Junker vibration tests, DIN concluded that helical spring washers cannot reliably prevent self-loosening of high-strength bolts under transverse vibration, and withdrew DIN 127 along with several other lock-washer standards. The washers themselves are still manufactured and widely used to the old specification for general-purpose assemblies.
How do wedge lock washers stop loosening?
Wedge lock washers are used in pairs with radial cams between them and serrations on the outer faces. The cam angle is greater than the thread pitch angle, so any rotation of the bolt in the loosening direction forces the cam faces to ride up and increase bolt tension instead of releasing it. The joint locks itself tighter the more it tries to loosen.
When is a wedge lock washer worth the extra cost?
Use wedge lock washers where vibration is severe and the cost of a loosened joint is high: rail and rolling stock, wind turbines, mining and construction equipment, structural steelwork, and heavy machinery. For general assemblies with light to moderate vibration, a DIN 127 spring washer remains an economical and widely accepted choice.