Accurate Shaft Connections for Industrial Power Transmission

A shaft key may be small, but an incorrectly specified one can compromise an entire mechanical drive. In compatible machinery, keys fit into matching keyways to transmit torque between a shaft & a pulley, sprocket, gear or coupling hub.

Whether you're replacing a damaged key, servicing a motor-driven assembly or preparing parts for a new machine, correct dimensions & fit matter more than appearance.

Industrial Shed's Keys & Keyways collection is intended to help Australian fitters, machinists, maintenance teams & industrial buyers understand the specifications needed to select compatible shaft connection components.

How to Select the Correct Shaft Key?

Start with the equipment manufacturer's drawing, part number or an undamaged original component.

Check these details before ordering:

• Key profile: Identify a parallel, Woodruff, tapered or other specified design.

• Width: Match the shaft & hub keyway requirements.

• Height: Confirm the key's cross-section & seating requirements.

• Length: Check the required engagement length.

• Material: Match the specified grade rather than substituting harder material.

• Dimensional standard: Confirm the applicable metric, imperial or manufacturer-specific specification.

• Condition of the connection: Inspect the shaft & hub keyways for wear or damage.

The available profiles, sizes & materials should be confirmed against individual product listings. Not every key design discussed in this guide is necessarily stocked in this collection.

What Are Shaft Keys & Keyways?

A shaft key is a mechanical element that fits into a machined recess to connect a shaft to a compatible hub.

The keyway is the slot or recess formed in the shaft or hub to accommodate the key.

Together, these features provide a keyed shaft-to-hub connection. The arrangement is commonly used where torque needs to pass between a rotating shaft & a mounted mechanical component.

A correct fit depends on the entire assembly—not just the key.

Parallel Keys for Industrial Machinery

Parallel keys have generally rectangular or square cross-sections with parallel faces.

They are used in many suitable shaft-to-hub connections, including certain pulleys, gears & coupling hubs.

When replacing a parallel key, check its width, height, length & specified tolerances. A nominal dimension does not establish whether the key fits correctly.

An undersized key may permit unwanted movement, while an oversized key can prevent proper assembly or damage the keyways.

Woodruff Keys & Curved Keyways

Woodruff keys have a segment-shaped profile that fits a matching curved recess in the shaft.

They are used in equipment designed for this particular connection.

Their dimensions are not interchangeable with ordinary parallel keys simply because their widths appear similar.

Use the correct designation & manufacturer requirements when replacing a Woodruff key.

Tapered Keys & Specialised Connections

Some machinery uses tapered or other specialised key arrangements.

These designs may have different fitting procedures & mechanical functions from parallel keys.

The original equipment specification should determine the correct replacement.

Avoid machining or modifying a key to create an approximate fit without an approved engineering procedure.

Metric vs Imperial Shaft Key Sizes

Australian industrial workshops may maintain machinery built to different dimensional standards.

Metric & imperial keys can look similar but differ enough to cause an incorrect fit.

For example, a nominal 8 mm key should not be assumed interchangeable with a nearby imperial dimension.

Check the shaft & hub specifications & use the relevant engineering standard where applicable.

Understanding Key Width, Height & Length

Parallel keys are often identified by three dimensions: width × height × length.

For example, an 8 × 7 × 40 mm designation describes a nominal key 8 mm wide, 7 mm high & 40 mm long.

The correct keyway dimensions & tolerances remain essential.

If the existing key is damaged, do not rely solely on measuring its worn surfaces.

Keys for Pulleys, Sprockets & Gears

A keyed connection may be used to transmit torque between a shaft & a drive component.

The key must suit the mounted hub, shaft & expected operating load.

For related mechanical drive parts, explore Chains & Sprockets.

If a key repeatedly becomes damaged, inspect the sprocket or pulley hub & the shaft rather than replacing only the key.

Keys for Taper Lock Bushes

Many keyed taper lock bush arrangements require a compatible shaft key.

The bush series, bore, keyway & shaft dimensions must match.

Explore Taper Lock Bushes & Hubs for related shaft-mounting components.

A key with the correct width but unsuitable height or length may still be incompatible.

Keys for Couplings & Motor Drives

Certain coupling hubs use keyed connections to transmit torque between shafts & connected equipment.

Check the coupling manufacturer's keyway & bore specifications before choosing a replacement.

Browse Rigid Couplings for related direct shaft connections.

Some couplings use keyless clamping arrangements, so a shaft key is not required in every installation.

Shaft Key Materials & Fit

Material selection is part of the mechanical design.

A key that is excessively hard, soft or otherwise unsuitable may behave differently under load.

Use the specified material & tolerances rather than assuming a stronger replacement is always preferable.

Where the original specification is unknown, obtain suitable engineering advice before substituting a different grade.

Why Shaft Keys Fail?

Shaft key damage can result from overload, poor fit, movement within the hub or other drive problems.

Common warning signs include deformation, fretting, loose fit & damaged keyway edges.

Inspect the complete connection before installing a replacement.

A new key cannot reliably compensate for a severely worn or incorrectly machined keyway.

Keyless Shaft Connections

Not all shaft-mounted components require conventional keys.

Some machinery uses alternative clamping or locking arrangements.

For related products, explore Shaft Collars & Locking Bushings.

The correct mounting method must suit the machine design.

Maintenance & Replacement Checklist

Before replacing a shaft key, isolate the equipment using the approved procedure.

Identify the key type, measure or verify the required dimensions & inspect both mating keyways.

Check for damaged hubs, shaft movement or evidence of excessive loading.

For broader mechanical servicing requirements, explore Drive Accessories & Maintenance.

Record the correct replacement specification for future maintenance.

Keys & Keyways FAQs

What Is a Shaft Key Used For?

A shaft key helps transmit torque between a shaft & a compatible mounted component. It fits into matching keyways to create the mechanical connection.

What Is the Difference Between a Key & a Keyway?

The key is the separate component used to transmit torque. The keyway is the machined recess that accommodates the key.

What Is a Parallel Key?

A parallel key has parallel faces & a generally rectangular or square cross-section. It is used in suitable keyed shaft-to-hub connections.

What Is a Woodruff Key?

A Woodruff key has a curved, segment-shaped profile. It fits into a matching shaft recess & must be selected to the original specification.

How Do I Measure a Shaft Key?

Confirm its required width, height & length from the equipment specification or an undamaged reference. Check the applicable tolerances & both mating keyways.

Are Metric & Imperial Keys Interchangeable?

Not automatically. Small dimensional differences can affect fit & performance, so use the specified standard.

What Causes a Shaft Key to Break or Wear?

Possible causes include overload, poor fit, misalignment or movement within the connection. Inspect the shaft & hub before fitting another key.

Can I Reuse a Damaged Shaft Key?

A damaged key should generally be replaced with the specified component. The keyways should also be checked for wear or damage before reassembly.

Why Choose Industrial Shed for Keys & Keyways?

Correct shaft keys & keyway components help maintain reliable torque transmission in compatible industrial drives. Accurate sizing, material selection & installation are essential.

Industrial Shed supports Australian fitters, machinists & maintenance teams with mechanical components & related workshop supplies.

For eligible parts enquiries, replacement assistance & warranty requirements, explore our Warranty & Parts Support service.