Duplex Tapered Bore Sprockets

What is a duplex tapered bore sprocket?

A duplex tapered bore sprocket is a sprocket with two rows of teeth, designed to run with duplex roller chain, and a tapered bore that accepts a standard tapered locking bush. Duplex chain has two rows of rollers side by side, giving more strength and power capacity than simplex chain, and the matching duplex sprocket has two closely spaced rows of teeth to engage both strands at once.

The tapered bore means the sprocket is fitted to the shaft with a tapered locking bush. When the bush screws are tightened, the bush is drawn into the tapered bore and clamps tightly onto the shaft. This gives a strong, self-centring, keyed connection that is quick to fit and remove, and allows the same sprocket to suit many shaft sizes simply by changing the bush.

A typical duplex tapered bore sprocket has:

• Two rows of teeth - matched to the pitch, roller size, and strand spacing of duplex roller chain
• Hub - an extended centre section that houses the tapered bore and supports the bush
• Tapered bore - accepts a standard tapered locking bush
• Half-threaded holes - shared with the bush, used to tighten the bush into the sprocket and to remove it
• Steel body - strong and durable, often with hardened teeth for longer wear life

Duplex tapered bore sprockets are usually described by:

• Chain size - such as 06B-2 for 3/8 inch pitch, 08B-2 for 1/2 inch pitch, or 10B-2 for 5/8 inch pitch British Standard duplex chain
• Number of teeth - such as 17, 19, 20, or 21 teeth, which sets the sprocket size and drive ratio
• Bush size - the tapered locking bush size the sprocket accepts, such as 1210, 1610, or 2012
• Pitch circle diameter - the effective working diameter of the sprocket

For example, a 19 tooth 06B duplex tapered bore sprocket has 19 teeth, suits 3/8 inch pitch British Standard duplex chain, and is fitted to the shaft with a tapered locking bush.

Key features:

• Duplex chain compatibility - two rows of teeth for higher-power duplex chain drives
• Keyless, self-centring mounting - fitted with a tapered locking bush for a strong, accurate connection
• Higher torque transmission - suited to drives that need more capacity than simplex chain
• Flexible shaft sizes - one sprocket suits many shaft sizes by changing the bush
• Quick fitting and removal - fitted and removed with simple hand tools
• No machining needed - no boring or keyway cutting in the sprocket itself
• Steel construction - strong and durable for industrial drives

In simple terms, a duplex tapered bore sprocket is a two-row sprocket for duplex chain that fits quickly and securely to a shaft with a tapered locking bush.

Why are duplex tapered bore sprockets essential?

Duplex tapered bore sprockets are essential for chain drives that need more power than simplex chain can provide, while remaining quick and easy to install and maintain. Sprockets with plain or pilot bores need to be machined, keyed, and secured to the shaft, which takes time and can be difficult to change later. A tapered bore sprocket fitted with a tapered locking bush gives a strong, accurate connection in minutes, and can be removed easily for maintenance.

Their main benefits are:

• Higher power transmission - duplex teeth suit drives that need more capacity than simplex chain
• Strong shaft connection - tapered locking bushes clamp firmly and transmit high torque
• Self-centring - the taper centres the sprocket accurately, reducing wobble and chain wear
• Quick installation - fitted in minutes with standard tools, with no machining
• Easy removal - the bush releases quickly for maintenance and replacement
• Flexible shaft sizes - change the bush to fit a different shaft diameter
• Reduced stock - one sprocket can suit many shaft sizes, reducing the range of parts needed
• Reduced downtime - faster fitting and removal keeps machinery running

Duplex tapered bore sprockets are used across a wide range of industries and applications, including:

• Industrial drives - medium and heavy-duty chain drives on machinery
• Conveyors - conveyor drives and transfer systems
• Agricultural machinery - drives on harvesters, balers, drills, and processing equipment
• Packaging and food machinery - drive systems on production lines
• Mining and quarrying - conveyors, screens, and crushers
• Pumps, compressors, and mixers - chain-driven equipment
• Timber, paper, and steel processing - drive systems and conveyors

The main types of duplex tapered bore sprockets

Duplex tapered bore sprockets are usually grouped by chain standard, chain size, tooth count, and bush size.

By chain standard:

• British Standard (BS) duplex sprockets - suit European-style duplex roller chains, such as 06B-2, 08B-2, 10B-2, and 12B-2
• ANSI duplex sprockets - suit American-style duplex roller chains, such as 40-2, 50-2, and 60-2

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

By chain size:

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

By number of teeth:

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

By bush size:

• Small bush sizes - such as 1008 and 1108, for smaller sprockets and shafts
• Medium bush sizes - such as 1210, 1610, and 2012, for general industrial drives
• Large bush sizes - such as 2517 and above, for larger sprockets and shafts

Related products:

• Tapered locking bushes - required to fit the sprocket to the shaft, chosen to match the bush size and shaft diameter
• Duplex platewheels - hubless duplex sprockets that can be bored, welded, or bolted
• Double simplex sprockets - sprockets with two widely spaced tooth rows for driving two separate simplex chains
• Duplex chain and links - matching chain and connecting links for duplex drives

How to choose the right duplex tapered bore sprocket?

Choosing the right 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 duplex chain
• Chain size - choose a sprocket that matches the chain pitch exactly, such as 08B-2
• Number of strands - make sure the sprocket is duplex, with two closely spaced rows of teeth for a single duplex chain. For two separate simplex chains, choose a double simplex sprocket instead
• Number of teeth - choose tooth counts on the drive and driven sprockets that give the required ratio. Larger sprockets give smoother running and less chain wear
• Bush size - check the sprocket’s bush size and choose a tapered locking bush with a bore that matches the shaft
• Shaft size - make sure the shaft diameter is within the bore range of the bush size
• 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 bush fit

How to fit a duplex tapered bore sprocket

Fitting the sprocket correctly helps the chain run smoothly:

• Isolate the drive - switch off and isolate the machine before starting work
• Clean the parts - clean the shaft, tapered bore, and bush, and remove any oil or grease from the taper
• Fit the bush - place the bush into the sprocket, line up the half holes, and insert the screws loosely
• Fit to the shaft - slide the sprocket and bush 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
• Tighten the bush - tighten the screws evenly and alternately to the recommended torque, rechecking alignment as you go
• Fit the chain - fit the duplex 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 duplex tapered bore sprockets

What is a duplex tapered bore sprocket?

It is a sprocket with two rows of teeth for duplex roller chain, with a tapered bore that accepts a tapered locking bush for quick, secure mounting on a shaft.

What does tapered bore mean?

A tapered bore sprocket has a tapered hole that accepts a tapered locking bush. The bush clamps onto the shaft when tightened, fixing the sprocket securely and centring it accurately.

Do I need to buy a tapered locking bush separately?

Usually, yes. Choose a bush that matches the sprocket’s bush size, with a bore and keyway that suit your shaft.

What does 06B mean on a duplex sprocket?

06B is the British Standard chain size for 3/8 inch pitch chain. A duplex sprocket marked 06B suits 06B-2 duplex roller chain.

What is the difference between duplex and double simplex sprockets?

A duplex sprocket has two closely spaced tooth rows for a single duplex chain. A double simplex sprocket has two tooth rows spaced further apart, so two separate simplex chains can run side by side.

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

No. Duplex sprockets have two rows of teeth and are designed to run with duplex 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.

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.

How do I remove a tapered bore sprocket?

Remove the screws from the bush, insert them into the removal holes, and tighten them to push the bush out of the taper. The sprocket can then be removed from the shaft.

Should I lubricate the taper?

No. The tapered surfaces should be clean and dry so the bush grips correctly. Only the chain needs lubrication.

When should I replace the 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.