Tab Washers

Reading the Tab: Internal, External, and Bend-Over Geometry

The tab's position decides what it restrains. Move the same tab from the inside of the bore to the outside of the rim, and you turn a shaft lock into a fastener lock. This is the most useful distinction when specifying the part, and the one most often left vague on a drawing.

An internal tab points inward into the bore and drops into a slot, keyway, or machined flat on a shaft, so the washer can no longer spin. An external tab points outward from the outer diameter: it bends up against one of the nut's flats, or down over the edge of a housing or into a drilled hole, anchoring the washer to the structure. A third family uses a straight arm instead of a bent ear, with the leg folded along a machined face so it locates and locks at the same time.

Whatever the style, the tab is the functional feature and the bore is the datum. A tab 0.2 mm short may not reach the nut flat after bending, and a bore 0.1 mm loose lets the washer chatter and wear the very flat it is meant to grip.

Tab Washers vs. Spring, Serrated, and Wedge-Lock Designs

Buyers usually arrive with one question: which locking washer actually works in this joint? The honest answer depends on what the joint must survive, so the table below compares the mainstream options by the principle each one uses.

The pattern is simple. Friction-based washers suit joints that stay cool, see moderate vibration, and rarely need inspection. A tab washer wins when the environment is hot, when the joint is safety-relevant, or when a crew must confirm the lock by eye without checking torque. A wedge-lock pair is the better answer when heavy dynamic load and repeated disassembly are both expected.

One caution: a positive lock, a split washer, and a serrated washer are often stacked on the same stud because an older drawing carried them over. Where a tab lock is used, an extra friction washer usually adds stack height and a second failure point without adding holding power. Decide which mechanism the joint relies on, then specify that one.

Selecting Forming Tab Material and Temper

Tabs offer opposing demands. The tab needs yield strength to keep its set, whereas the bend line needs ductility to fold without shattering. This makes material and temper more important than on a compacted flat washer.
Bend tabs are usually made of carbon and spring steels like 65Mn, which retain a permanent set neatly. For moisture, washdown, or salt, use 304 stainless steel for outdoor operations and 316 for chloride pitting. Anodising protects and colours aluminium 6061-T6 and 7075-T6 for visible, weight-sensitive hardware. Titanium Grade 5 is for weight-critical items, while brass and copper carry electricity.
Specify temper separately from grade. When a joint needs a precise blend of bendability and spring-back, we quench and temper, case harden, and precipitation harden aluminium alloys to HRC 20–62 and verify by batch testing.

Where Formed Tabs Earn Their Place

Positive locking appears wherever a joint runs hot, is hard to inspect, or is expensive to re-torque. Automotive and motorcycle assemblies use it on suspension, brake, and drivetrain hardware where vibration never stops. Robotics and automation use it on joints and axis hardware that must hold position without drift. Medical instruments specify stainless and titanium versions where cleanability matters, and consumer electronics use small brass and copper parts in bonding and grounding stacks.

Outdoor and marine products are a natural fit too: anodized aluminum and 316 stainless parts survive salt spray and washdown, and anodized color can double as a size code on the line. Bicycle, e-bike, and powersports builders use them on axle and rotor hardware, where a tab engaged with a dropout flat keeps a wheel aligned under braking.

The manufacturing requirement is the same everywhere: the tab must be formed to the drawing and the bore must be round. That is where a machined part earns its cost at low and mid volumes, because geometry can change between production runs without new tooling and prototypes match the eventual production part.

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