Zinc Plated Steel Keystock

Why zinc plating on a machine element?

Mostly for what happens before installation. Keystock is bought in stock lengths and cut as needed, which means a bar can sit in a drawer or on a rack for months between jobs. Bare steel bar in a workshop picks up surface rust quickly, and a rusty key is a problem for a reason that is easy to miss: the key has to slide into a keyway with a controlled side fit, and corrosion products add enough dimension to turn a snug fit into one that will not go in without filing. Zinc plating keeps the bar dimensionally clean on the shelf and adds a useful margin of corrosion resistance once the key is in a machine.

Why choose zinc plated steel keystock

• Steel gives the shear strength a key needs to transmit torque
• Predictable failure mode, shearing before the shaft or hub is damaged
• Zinc plating keeps stock bar clean and dimensionally accurate in storage
• Moderate corrosion protection in indoor machinery service
• Precision square section sized to standard keyway dimensions

Sizes stocked

• Small, 1/8, 5/32, 3/16, 1/4, and 5/16 inch square
• Mid range, 3/8, 7/16, 1/2, 9/16, and 5/8 inch square
• Large, 3/4, 7/8, and 1 inch square
• All supplied in 1 foot lengths
• Order by the keyway width, measured from the slot rather than the shaft

Common applications

• Pulley, sheave, and sprocket mounting on drive shafts
• Gearbox and gear assembly
• Electric motor and pump shaft connections
• Conveyor drives, rollers, and idlers
• Agricultural equipment and implement drives
• Machine repair and rebuild work

For round bar to machine into shafts and pins, see our unthreaded rods. Background on key sizing and fit is on our keystock page.

Related Categories

• Keystock
• Unthreaded Rods
• Threaded Rods
• Rods, Studs & Keystock
• Zinc Plated Keystock

Zinc Plated Keystock FAQs

Will the plating affect the fit?

Zinc plating is thin enough that keystock is supplied to correct dimension with the coating on. If a key is a fraction tight, light filing on the side faces is normal practice, though check the keyway for burrs first since that is the more common cause.

How do I cut keystock to length?

A hacksaw, bandsaw, or cutoff wheel all work. Deburr the cut end so it does not catch when the key is driven into the keyway, and dress the plating back if the cut has left a ragged edge.

Does the key need to be a driving fit?

Snug on the sides, tapped in rather than hammered. If a key requires heavy force it is oversized or the keyway has burrs. A key that falls in loosely will hammer under load and eventually wear the keyway oval.

Will zinc plated keystock corrode in a gearbox?

Inside an oil-filled housing, no. In an open drive exposed to weather, the plating gives useful protection but is not permanent. For sustained outdoor or washdown service, stainless keystock would be the better specification.

What size key does a 1 inch shaft take?

Conventionally a 1/4 inch key, but measure the keyway rather than relying on convention, since equipment varies and a previously repaired shaft may have a non-standard slot.

Can I use two shorter keys instead of one long one?

It is not ideal, since load rarely distributes evenly between them and one usually takes most of it. A single key running the full hub length is the correct approach where the geometry allows.