Triplex Sprockets

What is a triplex sprocket?

A triplex sprocket is a sprocket with three rows of teeth, designed to run with triplex roller chain. Triplex chain has three rows of rollers side by side, giving high strength and power capacity, and the matching triplex sprocket has three closely spaced rows of teeth to engage all three strands at once. Triplex sprockets are used in heavy-duty drives where high power and torque need to be transmitted in a compact space.

The triplex sprockets in this range have a hub and a pilot bore. The pilot bore is a small starter hole that can be machined out to fit the exact shaft size, with a keyway and set screw added as needed. This makes them versatile for new drives, repairs, and custom applications.

A typical triplex sprocket has:

• Three rows of teeth - matched to the pitch, roller size, and strand spacing of triplex roller chain
• Hub - an extended boss that supports the sprocket on the shaft and provides room for a keyway and set screw
• Pilot bore - a small starter bore that can be machined to the required shaft size
• Steel body - strong and durable, often with hardened teeth for longer wear life

Triplex sprockets are usually described by:

• Chain size - such as 06B-3 for 3/8 inch pitch, 08B-3 for 1/2 inch pitch, or 10B-3 for 5/8 inch pitch British Standard triplex chain
• Number of teeth - such as 10, 11, 17, or 22 teeth, which sets the sprocket size and drive ratio
• Bore type - such as pilot bore, ready to be machined to size
• Pitch circle diameter - the effective working diameter of the sprocket

For example, a 17-tooth 06B triplex pilot bore sprocket has 17 teeth, suits 3/8 inch pitch British Standard triplex chain, and has a pilot bore that can be machined to fit the shaft.

Key features:

• Triplex chain compatibility - three rows of teeth for high-power triplex chain drives
• High torque transmission - suited to heavy-duty drives and shock loads
• Pilot bore - can be machined to fit the shaft exactly, with a keyway and set screw added
• Hub design - gives a solid, stable mounting on the shaft
• Compact - carries more power than simplex or duplex sprockets of the same pitch
• Steel construction - strong and durable for industrial drives
• Range of sizes - available in many tooth counts and chain sizes

In simple terms, a triplex sprocket is a three-row sprocket that drives triplex chain, giving maximum power in a compact chain drive.

Why are triplex sprockets essential?

Triplex sprockets are essential for drives that need to transmit high power and torque without moving to a larger chain pitch. Larger pitch chains need bigger sprockets and run less smoothly at higher speeds. Triplex sprockets and chain allow a smaller pitch to carry much more power, keeping drives compact while still handling heavy loads, shock loads, and continuous operation.

Their main benefits are:

• Maximum power in a compact drive - higher capacity than simplex or duplex sprockets of the same pitch
• Smoother running - smaller pitches with three strands can run more smoothly than larger single-strand chains
• Positive drive - no slipping, keeping drives accurate and reliable
• Durable - handles heavy loads, shock, and continuous operation
• Custom bores - pilot bores can be machined to suit any shaft size within the sprocket’s range
• Strong mounting - the hub gives a secure fit on the shaft with a key and set screw
• Widely available - standard sizes make replacement sprockets easy to source

Triplex sprockets are used across a wide range of industries and applications, including:

• Heavy industrial drives - high-power chain drives on industrial machinery
• Conveyors - heavy-duty conveyor drives
• Mining and quarrying - crushers, screens, and conveyors
• Agricultural machinery - heavy-duty drives on harvesters and processing equipment
• Steel, paper, and timber processing - high-load drive systems
• Pumps, compressors, and mixers - chain-driven equipment with high torque
• Construction and plant machinery - heavy-duty power transmission

The main types of triplex sprockets

Triplex sprockets are usually grouped by chain standard, chain size, tooth count, and bore type.

By chain standard:

• British Standard (BS) triplex sprockets - suit European-style triplex roller chains, such as 06B-3, 08B-3, 10B-3, 12B-3, and 16B-3
• ANSI triplex sprockets - suit American-style triplex roller chains, such as 40-3, 50-3, 60-3, and 80-3

British Standard and ANSI chains are not interchangeable, so the sprocket must match the chain standard.

By chain size:

• 06B-3 (3/8 inch pitch) sprockets - for compact heavy-duty drives
• 08B-3 (1/2 inch pitch) sprockets - a popular size for general heavy-duty drives
• 10B-3 (5/8 inch pitch) sprockets - for higher power drives
• 12B-3 (3/4 inch pitch) and larger sprockets - for very heavy-duty drives

By number of teeth:

• Small sprockets - fewer teeth, used as drive sprockets on motors and gearboxes where space is limited
• Large sprockets - more teeth, used as driven sprockets to reduce speed and increase torque, and for smoother running

By bore type:

• Pilot bore sprockets - supplied with a small starter bore, ready to be machined to the exact shaft size, with a keyway and set screw added as needed
• Tapered bore sprockets - designed to accept a tapered locking bush for quick, keyless mounting

Related products:

• Triplex tapered bore sprockets - triplex sprockets designed for tapered locking bushes
• Triplex platewheels - hubless triplex sprockets that can be bored, welded, or bolted
• Triplex chain and links - matching chain and connecting links for triplex drives

How to choose the right triplex sprocket?

Choosing the right triplex sprocket means matching it to the chain, the shaft, and the drive. Work through these points in order:

• Chain standard - check whether the drive uses British Standard or ANSI triplex chain
• Chain size - choose a sprocket that matches the chain pitch exactly, such as 06B-3 or 08B-3
• Number of strands - make sure the sprocket is triplex, with three rows of teeth
• Number of teeth - choose tooth counts on the drive and driven sprockets that give the required ratio. As a guide, larger tooth counts give smoother running and less chain wear, especially at higher speeds
• Bore - check the pilot bore can be machined to your shaft size, leaving enough material in the hub for strength and a keyway
• Fixing method - plan how the sprocket will be fixed to the shaft, usually with a key and set screw
• Load and speed - check the chain size and sprocket suit the power and speed of the drive
• Space - check the pitch circle diameter, hub, and overall width fit the available space
• Quality and brand - choose sprockets from reputable suppliers for accurate teeth and reliable performance

How to fit a triplex sprocket

Fitting a triplex sprocket correctly helps the chain run smoothly:

• Machine the bore - bore the sprocket to the shaft size, keeping the bore concentric with the teeth
• Cut a keyway - add a keyway to suit the shaft key, and drill and tap a hole for a set screw if needed
• Isolate the drive - switch off and isolate the machine before fitting
• Fit to the shaft - slide the sprocket onto the shaft with the key in place
• Align the sprocket - position the sprocket so it lines up with the sprocket it drives, using a straight edge across the faces
• Secure the sprocket - tighten the set screw onto the key or shaft to stop the sprocket moving along the shaft
• Fit the chain - fit the triplex chain and set the tension, leaving a small amount of slack on the slack side
• Check the drive - turn the drive by hand to check the chain runs smoothly, then lubricate before running

FAQ - All you need to know about triplex sprockets

What is a triplex sprocket?

A triplex sprocket is a sprocket with three rows of teeth, designed to run with triplex roller chain in heavy-duty, high-power drives.

What does pilot bore mean?

A pilot bore is a small starter hole in the centre of the sprocket. It is designed to be machined out to the exact shaft size, usually with a keyway and set screw added.

What does 06B mean on a triplex sprocket?

06B is the British Standard chain size for 3/8 inch pitch chain. A triplex sprocket marked 06B suits 06B-3 triplex roller chain.

Can I use a triplex sprocket with simplex or duplex chain?

No. Triplex sprockets have three rows of teeth and are designed to run with triplex chain only.

What is the difference between BS and ANSI sprockets?

BS sprockets suit British Standard chain, and ANSI sprockets suit American Standard chain. They have different tooth dimensions and are not interchangeable.

What is the difference between pilot bore and tapered bore sprockets?

Pilot bore sprockets are machined to fit the shaft and fixed with a key and set screw. Tapered bore sprockets accept a tapered locking bush, giving quick, keyless mounting and allowing one sprocket to fit different shaft sizes.

How do I work out the drive ratio?

Divide the number of teeth on the driven sprocket by the number of teeth on the drive sprocket. For example, a 17 tooth drive sprocket and a 51 tooth driven sprocket give a 3:1 ratio, reducing speed to a third and increasing torque.

Why should I avoid very small sprockets?

Sprockets with very few teeth cause the chain to bend more sharply, which increases wear, vibration, and noise. Where space allows, larger sprockets give smoother running and longer chain life.

Do triplex sprockets need lubrication?

The chain running on the sprocket should be lubricated regularly to reduce wear. The sprocket itself does not need separate lubrication.

When should I replace a triplex sprocket?

Replace it if the teeth are hooked, pointed, or worn, as worn sprockets quickly wear new chain. It is good practice to check sprockets whenever the chain is replaced.