Stainless Steel Spring Washer

Choosing the Right Spring Washer
1) What does a spring washer do & when should you use it?

A spring washer (typically split / helical type) is a slightly twisted ring with a cut that provides:

A small amount of elasticity in the bolted joint

Increased contact pressure at the interface

Some resistance to loosening under vibration and shock (limited)

Use a spring washer when:

You want basic anti-loosening help in non-critical joints

The assembly faces light vibration or movement

You need a simple, low-cost method to maintain contact between nut/bolt and bearing surface

Important: Modern engineering practice treats split spring washers as limited anti-vibration devices. For highly critical joints, use nylock nuts, prevailing torque nuts, chemical thread-lockers, double nuts, or structural lock systems instead.

2) Environment & corrosion – choosing the spring washer material

Indoor / dry / general machinery & fabrication:

Use MS (mild steel) spring washers with black, phosphated or zinc-plated finish.

Suitable for general equipment, machines, fabrications, panels.

Outdoor / mild corrosion / galvanized structures:

Use MS spring washers with zinc plating / hot-dip galvanizing.

Match the coating system of bolts and nuts (e.g. HDG bolts → HDG spring washers).

Stainless assemblies / food / pharma / decorative:

Use stainless spring washers:

SS 304 (A2) – for general outdoor, food equipment, stainless structures

SS 316 (A4) – for coastal, marine, chemical, and wash-down environments

Best practice:

Wherever possible, match spring washer material to the bolt & nut material and the environment to avoid galvanic corrosion and staining.

3) Size & standard – matching bolt size and thickness

Spring washers are sized to suit the bolt diameter:

Inner diameter (ID):

Sized to clear the bolt shank; e.g., M10 spring washer for M10 bolt.

Too large ID reduces effective contact and locking effect.

Outer diameter (OD):

Standard OD for normal duty.

Larger OD variants exist, but plain washers are usually preferred for load spreading.

Thickness & section height:

Standard thickness for typical anti-loosening function.

Heavier sections are used for larger diameters and higher loads.

Rule:
For standard metric bolts → use the corresponding size spring washer as per DIN/ISO for that bolt.

Mechanical Properties (Guide) – Spring Washer

Mechanically, spring washers are defined by their material, hardness, and spring characteristics (deflection vs load). Their function is to provide elastic preload and edge friction under the nut/bolt head.

1) Mild steel spring washers (standard)

Typical characteristics:

Material: low carbon or medium carbon steel, hardened & tempered.

Hardness: higher than standard plain washers, to keep spring effect and resist flattening.

Functional behaviour:

Provide a small elastic deflection when compressed under the bolt/nut.

Edge of the cut section bites slightly into the nut/bolt and the bearing surface, increasing friction.

Under very high preload, they can flatten permanently, losing their spring action.

Use them with standard bolts in general duty applications, not as the only locking mechanism in critical joints.

2) Stainless steel spring washers (A2 / A4)

Typical characteristics:

Material: A2 (304) or A4 (316) stainless steel.

Corrosion resistant and suitable for stainless assemblies.

Spring characteristics slightly different (modulus and hardness) from hardened carbon steel, but still provide useful deflection for normal tightening ranges.

Functional behaviour:

Ideal where corrosion resistance is important (outdoor, food plant, marine).

Less prone to rust but can still lose spring action if over-compressed.

Must be used with matched stainless nuts & bolts to avoid galvanic issues and staining.

3) Behaviour in a bolted joint

In a properly tightened joint with a spring washer:

The washer is compressed and exerts a reaction force against nut/bolt head and surface.

This helps maintain contact pressure even if minor relaxation or embedding occurs.

The cut ends may apply local biting action, adding some friction to rotation.

Limitations:

Once the joint is fully tightened, most of the locking still comes from bolt tension and friction in threads & underhead; the spring washer adds only a small additional effect.

If it is flattened fully or permanently deformed, its spring function is largely lost.