Keyless Bushes

What is a keyless bush?

A keyless bush is a compact shaft locking device that fixes a pulley, sprocket, gear, cam, or other hub onto a shaft without a keyway, spline, or set screw. Most keyless bushes use a single-nut design. Inside the bush is a slotted sleeve with tapered surfaces. When the nut is tightened, the tapers are drawn together, so the bush grips the shaft on the inside and expands into the hub bore on the outside. This locks the hub and shaft together by friction, creating a strong, secure, backlash-free connection.

Because there is no key or keyway, the hub can be fixed at any position and angle along the shaft. This makes keyless bushes ideal for precise timing, fine adjustment, and small or compact drives where machining keyways would be difficult or would weaken the shaft.

A typical keyless bush has:

• Inner sleeve - a slotted sleeve that clamps onto the shaft
• Outer sleeve - a tapered sleeve that expands into the bore of the hub
• Locking nut - a single nut that draws the sleeves together when tightened, creating the clamping force
• Plain bore and outside diameter - sized to fit the shaft and the hub bore

Key features:

• Keyless connection - no keyway, spline, or set screw needed
• Zero backlash - creates a tight, play-free connection for reversing and precise drives
• Infinite positioning - fix the hub at any angle and position on the shaft
• Single-nut fitting - quick and simple to fit and adjust using a spanner
• Compact design - ideal for small shafts and limited space
• Protects the shaft - no keyway to weaken the shaft and no set screw to mark it
• Easy removal and adjustment - loosen the nut to reposition or remove the hub
• Metric and imperial sizes - available to suit a wide range of shafts and hub bores

In simple terms, a keyless bush is a compact, single-nut locking device that grips a hub tightly onto a shaft, giving a precise, play-free connection without a key.

Why are keyless bushes essential?

Keyless bushes are essential because many drives need a hub that is fixed securely, positioned precisely, and easy to adjust. Keyed connections can wear and develop play, especially in reversing or stop-start drives, and cutting keyways into small shafts can be difficult and weaken them. Set screws can mark the shaft and work loose under vibration. Keyless bushes avoid these problems with a strong, accurate, and adjustable connection.

Their main benefits are:

• No backlash - ideal for reversing drives, indexing, and accurate positioning
• Precise timing - hubs, cams, and gears can be set to the exact angle needed
• Quick adjustment - loosen one nut to reposition the hub, then retighten
• Stronger shafts - no keyway means the shaft keeps its full strength
• Lower machining costs - plain shafts and bores are quicker and cheaper to produce
• Reliable grip - even clamping around the shaft resists slipping and vibration
• Less wear - no movement between parts, so less fretting and keyway wear
• Faster maintenance - components can be released and removed easily

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

• Power transmission - fixing pulleys, sprockets, and gears to shafts
• Packaging and labelling machinery - precise timing of cams, rollers, and gears
• Printing and paper machinery - accurate positioning of rollers and drives
• Automation and robotics - backlash-free connections for actuators and drives
• Conveyors - mounting sprockets, pulleys, and rollers
• Food and pharmaceutical equipment - compact, easy-to-adjust drive connections
• Instruments and small machinery - small shafts where keyways are impractical
• Agricultural and general machinery - quick, reliable hub mounting

The main types of keyless bushes

Keyless bushes are usually grouped by size, measurement system, and material.

By size and duty:

• Mini keyless bushes - compact bushes designed for small shafts and hubs, ideal for light drives, instruments, and small machinery
• Standard keyless bushes - for general power transmission on medium-sized shafts
• Heavy-duty keyless bushes - for larger shafts and higher torque applications

By measurement system:

• Metric keyless bushes - for metric shafts and hub bores, described by shaft diameter, hub bore, and length, such as 8 × 19 × 22 mm
• Imperial keyless bushes - for inch shafts and hub bores, such as 3/16 inch shaft sizes

By material and finish:

• Steel keyless bushes - the standard choice for general industrial use
• Plated keyless bushes - give improved corrosion resistance for damp environments
• Stainless steel keyless bushes - for food, pharmaceutical, washdown, and corrosive environments

Related products:

• Keyless locking elements - tapered ring sets and locking assemblies that use several screws to clamp larger hubs and transmit higher torque
• Tapered locking bushes - keyed bushes that fit components with a tapered bore
• Shaft collars - clamp onto a shaft to position or retain components

How to choose the right keyless bush?

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

• Shaft diameter - choose a bush with a bore that matches the shaft diameter exactly
• Hub bore - choose a bush with an outside diameter that matches the bore of the pulley, sprocket, gear, or hub
• Hub length - check that the bush length suits the length of the hub, so it grips properly
• Metric or imperial - check whether the shaft and hub are metric or imperial, and choose a matching bush
• Torque - check that the bush can transmit the required torque, including starting loads, shock loads, and reversals
• Axial loads - consider any axial forces the connection must carry
• Hub strength - make sure the hub has enough wall thickness to withstand the clamping pressure without cracking or distorting
• Space - check that there is room for the nut and a spanner to tighten it
• Shaft and bore tolerances - make sure the shaft and hub bore are within the tolerances recommended by the manufacturer
• Environment - choose plated or stainless steel bushes for damp, washdown, or corrosive conditions
• Quality and brand - choose bushes from reputable suppliers for accurate dimensions and reliable clamping

FAQ - All you need to know about keyless bushes

How does a keyless bush work?

When the locking nut is tightened, tapered sleeves inside the bush are drawn together. This makes the bush grip the shaft and expand into the hub bore, locking the hub and shaft together by friction.

What do the sizes on a keyless bush mean?

Metric keyless bushes are usually described by shaft diameter, hub bore, and length. For example, 8 × 19 × 22 mm suits an 8 mm shaft and a 19 mm hub bore, with a 22 mm length.

What are the advantages over a keyed connection?

Keyless 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 quick to adjust and remove.

What is the difference between a keyless bush and a keyless locking element?

A keyless bush is usually a compact, single-nut design, ideal for smaller shafts and quick fitting. A keyless locking element uses tapered rings and several screws or a clamping flange, and is often used for larger hubs and higher torque.

Do I need a special hub for a keyless bush?

The hub needs a plain, parallel bore of the correct size and tolerance, with enough wall thickness to take the clamping pressure. No keyway or taper is needed.

How do I fit a keyless bush?

Clean the shaft, hub bore, and bush. Slide the bush into the hub and onto the shaft, position the hub where it is needed, then tighten the nut to the recommended torque using a spanner. Hold the hub or shaft to stop it turning while tightening.

How do I remove or adjust a keyless bush?

Loosen the locking nut to release the clamping force. The hub can then be repositioned or removed. If it does not release straight away, a light tap on the nut can help free the tapers.

Can keyless bushes be reused?

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

Why is my hub slipping on the shaft?

Common causes include a nut that is not tightened to the correct torque, oil or dirt on the clamping surfaces, incorrect shaft or bore tolerances, or a torque load higher than the bush can transmit.

Can keyless bushes be used on stainless steel shafts?

Yes. Choose a bush size and material suitable for the application, and use stainless steel bushes where corrosion resistance is important.