Drivelock Bushes

What is a Drivelock bush?

A Drivelock bush is a keyless shaft locking device used to fix pulleys, sprockets, gears, couplings, and other hubs securely onto a shaft. Instead of using a key and keyway, a Drivelock bush uses tapered rings that are pressed together by clamping screws. As the rings move together, the inner ring contracts onto the shaft and the outer ring expands into the hub bore, creating a high clamping force that locks the hub and shaft together by friction.

This gives a strong, backlash-free connection that can be positioned anywhere along the shaft and at any angle. Because no keyway is needed, the shaft keeps its full strength, and components can be fitted, adjusted, and removed quickly with standard tools.

Drivelock bushes are made in two main styles:

• Ring element sets - pairs of thin, tapered inner and outer rings that are clamped together by a separate pressure flange and screws
• Locking assemblies - complete units with built-in clamping screws, designed to be fitted directly between the shaft and hub

A typical Drivelock locking assembly has:

• Inner ring - contracts onto the shaft as the screws are tightened
• Outer ring - expands into the bore of the hub
• Clamping ring or flange - pushes the tapered rings together
• Clamping screws - a ring of screws that are tightened evenly to create the clamping force
• Release threads - threaded holes that help push the rings apart when removing the bush

Key features:

• Keyless connection - no keyway, spline, or set screws needed
• Zero backlash - a tight, play-free connection, ideal for reversing and stop-start drives
• Infinite positioning - the hub can be fixed at any position and angle on the shaft
• High torque transmission - transmits torque, axial loads, and bending loads by friction
• Protects the shaft - no keyway to weaken the shaft and no set screws to mark it
• Easy fitting and removal - fitted and released with standard hand tools, without heating or pressing
• Range of sizes - available for small and large shafts and hubs

In simple terms, a Drivelock bush is a set of tapered rings that clamps a hub tightly onto a shaft, giving a strong, play-free connection without a key.

Why are Drivelock bushes essential?

Drivelock bushes are essential because many machines need a secure, accurate, and adjustable connection between shafts and hubs. Keyed connections can wear and develop play, especially in reversing or shock-loaded drives, and keyways weaken the shaft and add machining cost. Set screws can mark the shaft and loosen under vibration. Drivelock bushes avoid these problems with a strong, precise connection that is quick to fit and adjust.

Their main benefits are:

• No backlash - ideal for reversing drives, indexing, and accurate positioning
• Precise adjustment - hubs, gears, and cams can be set at the exact angle and position needed
• Stronger shafts - no keyway means the shaft keeps its full strength
• Lower machining costs - plain shafts and bores are quicker and cheaper to produce than keyways
• Reliable torque transmission - high clamping pressure transmits heavy loads securely
• Reduced wear - no movement between parts, so less fretting and keyway wear
• Quick maintenance - components can be released and removed easily, reducing downtime
• Versatile - suits a wide range of shaft sizes, hubs, and applications

Drivelock bushes are used across a wide range of industries and applications, including:

• Power transmission - fixing pulleys, sprockets, and gears to shafts
• Couplings - mounting shaft couplings to motors, gearboxes, and pumps
• Conveyors - fixing drive drums, pulleys, and sprockets
• Packaging and printing machinery - precise timing of rollers, gears, and cams
• Machine tools and automation - backlash-free connections for drives and positioning systems
• Pumps, fans, and compressors - mounting impellers, hubs, and couplings
• Agricultural and construction machinery - fixing hubs and drive components
• Heavy industry - mining, steel, and processing equipment

The main types of Drivelock bushes

Drivelock bushes are usually grouped by their style and how they are clamped.

Ring element sets:

• Tapered ring pairs - simple sets of an inner and outer tapered ring. They need a separate clamping flange and screws to press the rings together. They are compact, economical, and suit lower to medium torque applications
• Multiple ring sets - two or more ring pairs can be fitted together to increase torque capacity, with each extra set adding additional capacity
• Small ring elements - compact rings for small shafts and light drives

Locking assemblies:

• Self-contained locking assemblies - complete units with built-in clamping screws, which fit directly into the hub without a separate flange. They are quick to fit and can transmit high torque
• Self-centring locking assemblies - designed to centre the hub accurately on the shaft, ideal where concentricity is important
• Compact locking assemblies - shorter or slimmer designs for limited space and narrow hubs
• Heavy-duty locking assemblies - designed for larger shafts and very high torque

By screw thread size:

• Clamping screw sizes - locking assemblies use clamping screws in different thread sizes, which affect the tightening torque and the clamping force. Always use the screws and torque recommended for the size

How to choose the right Drivelock bush?

Choosing the right Drivelock bush means matching it to the shaft, the hub, and the loads in the application. Work through these points in order:

• Shaft diameter - choose a bush with an inner diameter that matches the shaft
• Hub bore - choose a bush with an outer diameter that matches the bore of the hub
• Width - check that the width of the bush suits the length of the hub
• Style - choose ring element sets for simple, economical connections with an external clamping flange, or locking assemblies for quick fitting and higher torque
• Torque - check that the bush can transmit the required torque, including starting loads, shock loads, and reversals
• Axial and bending loads - consider any axial forces or bending moments the connection must carry
• Number of ring sets - for ring elements, use more than one set if extra torque capacity is needed
• Hub strength - make sure the hub has enough wall thickness to withstand the clamping pressure
• Concentricity - choose a self-centring locking assembly where accurate centring is needed
• Shaft and bore tolerances - make sure the shaft and hub bore are machined to the recommended tolerances
• Environment - consider corrosion-resistant versions for wet or corrosive conditions
• Quality and brand - choose bushes from reputable suppliers for accurate dimensions and reliable clamping

FAQ - All you need to know about Drivelock bushes

How does a Drivelock bush work?

Tapered rings inside the bush are pressed together by clamping screws. As they move together, the inner ring contracts onto the shaft and the outer ring expands into the hub, locking the two together by friction.

What do the sizes on a Drivelock bush mean?

Sizes are usually given as shaft diameter × hub bore × width. For example, 40 × 65 × 34 mm suits a 40 mm shaft and a 65 mm hub bore, with a width of 34 mm.

What is the difference between a ring element set and a locking assembly?

A ring element set is a simple pair of tapered rings that needs a separate clamping flange and screws. A locking assembly is a complete unit with built-in screws, making it quicker to fit and able to transmit higher torque.

What are the advantages over a keyed connection?

Drivelock bushes have no backlash, do not weaken the shaft with a keyway, allow the hub to be positioned at any angle and position, and are easy to adjust and remove.

Can I use more than one ring element set?

Yes. Fitting two or more sets together increases the torque capacity, although each additional set adds less than the first. Follow the manufacturer’s guidance on the number of sets.

How do I fit a Drivelock locking assembly?

Clean the shaft, hub bore, and bush, and apply light oil if the manufacturer recommends it. Slide the bush into the hub and onto the shaft, position the hub, then tighten the clamping screws gradually and evenly, working around the bush in several stages until they reach the recommended torque.

How do I remove a Drivelock bush?

Loosen the clamping screws gradually and evenly. If the rings do not release, fit screws into the release threads to push the rings apart.

Do I need a special hub for a Drivelock bush?

The hub needs a plain bore of the correct diameter and tolerance, with enough wall thickness to withstand the clamping pressure. No keyway or taper is required. Ring element sets also need a clamping flange and screws.

Can Drivelock bushes be reused?

Yes, they can usually be reused if they are clean, undamaged, and show no signs of wear or scoring. Check the rings and screws carefully before refitting.

Why is my hub slipping on the shaft?

Common causes include screws not tightened to the correct torque, uneven tightening, incorrect shaft or bore tolerances, too few ring sets, or a load higher than the bush can transmit. Check the fitting and the bush’s rating.