Stainless Steel Tab Washer

Choosing the Right Tab Washer

(Lock Washer with Bendable Tabs)

1) What does a tab washer do & when should you use it?

A tab washer is a thin lock washer with one or more bendable tabs that can be folded:

Up against a nut/bolt head flat

Or into a keyway / slot / hole in the mating part

Its job is to:

Mechanically lock the nut/bolt so it cannot rotate

Provide a positive, visible lock that’s easy to inspect

Prevent loosening in vibration, shock, or safety-critical applications

Use a tab washer when:

You need a firm mechanical lock, not just friction

The connection is safety-critical or difficult to re-tighten regularly

The design includes keyways, slots, or shoulders to locate the inner tab

You want a simple lock that doesn’t rely on friction or chemical thread-lockers

Typical applications:

Gearbox bearing lock nuts

Shaft nuts and hub nuts

Couplings, sprockets, pulleys

Railway, defence, heavy machinery & rotating equipment

2) Common types of tab washers – which to choose?
a) Single Tab Washer

Has one outer locking tab that is bent up against a nut/bolt flat.

Usually has an inner tab or tang that fits into a keyway or slot on the shaft or housing → prevents the washer itself from turning.

Use for:

Shaft nuts / lock nuts on bearings, gears, couplings.

Applications with a keyway or slot for the inner tab.

b) Double Tab Washer

Has two opposite outer tabs.

One or both tabs can be bent up against different flats of the nut.

Often also has an inner tab or locating feature.

Use for:

Heavier-duty applications where you want two locking points.

Places where the nut can be locked against two different flats for extra security.

c) Tab Washer with Multiple Outer Tabs / Star-Type Tabs

Several outer tabs around the OD → multiple locking options around the nut.

You choose the tab that aligns best with a nut flat and bend it up.

Use for:

General machinery where nut position can vary; having more tabs gives more flexibility.

3) Environment & corrosion – choosing material & finish

Indoor / dry / general machinery & gearboxes:

MS (mild steel) tab washers, often zinc-plated or oiled.

Suitable for gearboxes, shafts, bearings, couplings, internal machine assemblies.

Outdoor / exposed industrial environments:

Zinc-plated or thicker-coated MS tab washers.

Used in general outdoor machinery and structures, where corrosion protection is needed but not extreme.

Stainless / food / pharma / marine / chemical:

SS 304 (A2) tab washers – for stainless shafts and assemblies, general outdoor and food-grade use.

SS 316 (A4) tab washers – for coastal, marine and aggressive chemical environments.

Best practice: match tab washer material with the nut/bolt and environment to avoid galvanic corrosion and premature rusting.

Mechanical Properties (Guide) – Tab Washer

Tab washers are locking elements, not primary structural load carriers. Key properties are material strength, ductility for bending, and ability to maintain tab shape under service loads and vibration.

1) Mild Steel Tab Washers (Standard)

Typical characteristics:

Material: low or medium carbon steel, chosen for good formability and adequate strength.

Usually stamped and then heat-treated or work-hardened to balance ductility and stiffness.

Functional behaviour:

Outer locking tabs are bent up after tightening the nut/bolt.

Inner tab/tang fits into a keyway or locating slot, preventing rotation of the washer.

Once bent, the tabs provide a mechanical stop – nut cannot rotate without physically deforming the tab.

Design behaviour:

Must be ductile enough to bend once or twice without cracking.

Must be stiff enough that the tab holds its shape and does not spring back or fold under vibration.

In bending, the tab yields locally, then “locks” in place.

2) Stainless Steel Tab Washers (A2 / A4)

Typical characteristics:

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

Provide corrosion resistance with good ductility for tab bending.

Functional behaviour:

Same locking principle as MS tab washers, with added corrosion protection.

Used on stainless shafts, marine drives, food and pharma machinery, where rust is unacceptable.

Special notes:

Stainless is tougher; bending force may be slightly higher than for mild steel.

Correct tab bending tools and technique help avoid local cracking, especially in cold environments.

3) Strength & performance in the joint

In a properly designed and installed tab washer system:

The nut or bolt is tightened to the required torque for preload.

After tightening, one or more tabs are bent up against flats of the nut/bolt head:

Any rotation of the nut tends to push against the tab, which is anchored at its inner tab/keyway.

Rotation can only happen if the tab is forced to plastically deform further, which requires substantial additional force.

Performance characteristics:

Provides very high resistance to loosening from vibration and shock, because locking is mechanical, not purely frictional.

Locking condition is visually inspectable – you can see the tab in contact with the nut flat.

Tabs should not be bent back and forth many times; they are meant for 1–2 bend cycles (tighten → lock, possibly unlock once, then replace).

Failure/limit modes:

Tab cracking if over-bent or repeatedly bent back-and-forth.

Washers deforming if material is too soft or too thin for the nut/bolt size and service loads.

Inner tab failure if keyway fit is poor, leading to washer rotation.