Spring Washers Explained: Types, Load Curves, Standards and Sourcing Checks

On a DIN 127 B washer for M10, the free height sits only a few tenths of a millimetre above the material thickness. Across the common M8 to M12 sizes that working stroke is usually somewhere between 0.4 mm and 0.8 mm, and that small number is the entire function of the part. It is the distance over which the washer can push back.

Everything else follows from that sentence. It says what the part does, which is to store and return energy; where it acts, which is between the fastener and the joint face; and how it should be specified, which is by deflection and load rather than by thickness alone. It also explains why spring washers disappoint when they are bought as a locking device instead of an elastic element.

What a Spring Washer Actually Does

A spring washer keeps clamp load alive by staying partly deflected, so small amounts of settling, wear and thermal movement are absorbed instead of leaving the bolt loose.

Three jobs usually get bundled into one part. The first is preload compensation: paint, gaskets, soft platings and joint embedment all let the clamped stack shorten after assembly, and a washer with reserve deflection follows that movement. The second is vibration resistance, not by locking but by keeping a minimum preload on the thread so friction stays in the range that resists rotation. The third is axial take-up, which is why wave and curved washers turn up in bearing arrangements where end play has to be held within a few hundredths of a millimetre.

The locking claim is where the confusion starts. In Junker type transverse vibration tests, a split helical washer often performs no better than a plain hardened washer, and in some joint setups it performs worse, because the split ends act as a ramp once the washer has flattened. What a spring washer reliably does is store elastic energy. Whether that stops a bolt from rotating depends on joint stiffness, preload and the surface under the head.

Types of Spring Washers and What Each One Buys You

Spring washer families differ mainly in how much axial travel they offer and how much load they build over that travel. Our spring washer range follows the same split, from split lock rings through to thin corrugated washers, and the standards below are the ones most drawings reference.

Split lock washers to DIN 127 A and B are the default in general machinery because they are cheap, widely stocked and easy to spot on an assembly line. Their load curve climbs quickly and then flattens, so the usable travel is smaller than the free gap suggests.

Wave spring washers, such as DIN 137 B or the JIS B 1251 WW series, place several crests around the ring. Load is lower but progressive, and a thin wave washer fits inside bearing housings and small stacks where a split ring simply will not go.

DIN 137 B Wave Spring WashersWave-profile spring washers for low-to-medium loads and limited axial space, offering progressive elastic preload in compact electrical, instrument, and light machinery assemblies.View Product →

Curved washers, including DIN 128 A and DIN 137 A, are domed rather than corrugated. They give a short, stiff travel that suits bearing preload and end play control far more than a general bolted joint.

DIN 128 A Curved Spring WashersCurved spring washers for general threaded connections, providing short, stiff travel and elastic rebound to help maintain contact pressure under low-to-medium loads.View Product →

Disc springs to DIN 2093 sit at the other end of the scale: almost no travel, very high load, and a stack that can be tuned by arranging discs in series or in parallel.

Where Spring Washers Help and Where They Cause Trouble

Spring washers earn their place in joints that move, settle or grow, and they cause problems in joints that are already rigid and heavily preloaded.

The deciding factor is joint stiffness. In a stiff, well-preloaded joint the bolt behaves like a spring far stiffer than the washer, so the washer contributes very little to clamp load. In a soft joint the clamped parts dominate and the washer travel is worth much more. That is why two engineers can test the same washer and reach opposite conclusions.

Five Checks Before You Release a Purchase Order

Match the washer to the bolt, the joint and the environment, in that order, and most field failures disappear before the part is made.

1. Match hardness to the bolt. Hardened carbon spring steel in the 44 to 50 HRC range is normal against 8.8 and 10.9 bolts. A washer much softer than the bolt face embeds, and the preload you calculated never reaches the joint.
2. State the travel you need. Add joint settlement, coating crush and thermal movement, then confirm the washer still has reserve deflection at working load instead of sitting flat.
3. Check the bearing area. The outside diameter has to cover the clearance hole and the contact face. A washer bridging a slot or an oversized hole bends and takes a permanent set.
4. Read the environment. Electroplated washers at high hardness need a post-plate bake to lower hydrogen embrittlement risk, and standard carbon spring steel starts to lose temper above roughly 200 to 250 degrees Celsius, where stainless becomes the safer choice.
5. Write the full callout. Spring washer DIN 127 B, M10, stainless 1.4310 leaves little to interpretation; lock washer M10 leaves almost everything open.

If you are still deciding between a flat washer and a spring washer for a specific joint, this overview of washer types and their functions is a useful starting point before the drawing is released.

Inspection, Coating and Sourcing Risks

Most spring washer complaints at goods-in are not metallurgical. They come from height, hardness and plating, in that order.

Hydrogen embrittlement deserves the closest attention. A hard, electroplated washer held under load for weeks can crack without warning. Baking after plating, or switching to a mechanical coating, removes most of that exposure.

Standard mismatch is the second common problem. DIN 127 and ASME B18.21.1 split washers are not interchangeable: outside diameter, thickness and section height all differ, so a washer that meets the DIN table can sit outside the bearing area of an inch drawing, and the other way round.

For stainless assemblies, galling matters more than strength. A2 or A4 washers against stainless bolts can seize, and a slightly different alloy or a dry lubricant on the contact face solves more problems than a higher torque figure.

A practical goods-in check covers the following points:

• Free height and gap measured at a defined load
• Hardness checked on at least three parts per lot
• Coating thickness on faces and in recesses
• Split position and end squareness on split lock washers
• Bake or coating certificate after electroplating
• Heat number and material certificate for traceability

Frequently Asked Questions

What is the difference between a spring washer and a lock washer?

In practice the terms overlap. A spring washer is defined by its elasticity and is chosen for travel and load; a lock washer is defined by the intention to resist loosening. Many split lock washers are spring washers, but a wave washer or a disc spring is a spring washer that nobody would call a lock washer.

Do spring washers stop bolts from vibrating loose?

They help only while they remain deflected. Once a split washer flattens, its contribution to friction is close to that of a flat washer. Controlled preload, correct torque and a properly designed joint do more for vibration resistance than the washer alone.

When should a spring washer be left out?

Avoid them in joints that need defined gasket compression, in high strength connections designed to a torque specification, and on hardened ground faces where there is no settlement to absorb. In those cases a flat hardened washer, or no washer at all, is the better choice.

Which standard should I order to, DIN 127 or ASME B18.21.1?

Follow the dimensional system on the drawing. Metric designs normally reference DIN 127 A or B, JIS B 1251, or a company standard based on them; inch designs typically use ASME B18.21.1. The two families differ in outside diameter and thickness, so mixing them changes the bearing area as well as the height.