Double Simplex Sprockets

What is a double simplex sprocket?

A double simplex sprocket is a sprocket with two separate rows of simplex teeth on a single body, designed to drive two independent single-strand simplex roller chains at the same time. It is commonly used to pass drive from one chain to another along a line of shafts, or to drive two separate outputs from one shaft.

Unlike a duplex sprocket, which has two rows of teeth set close together to suit a single double-strand chain, a double simplex sprocket has its two tooth rows spaced further apart, so two separate simplex chains can run side by side without touching.

The double simplex 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 very versatile for new drives, repairs, and custom applications.

A typical double simplex sprocket has:

• Two rows of simplex teeth - each matched to the pitch and width of simplex roller chain, spaced apart so two chains can run independently
• 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

Double simplex sprockets are usually described by:

• Chain size - such as 06B for 3/8 inch pitch or 08B for 1/2 inch pitch British Standard simplex chain
• Number of teeth - such as 12, 13, 14, or 16 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 12 tooth 08B pilot bore double simplex sprocket has two rows of 12 teeth, each suiting 1/2 inch pitch British Standard simplex chain, and a pilot bore that can be machined to fit the shaft.

Key features:

• Drives two chains at once - two separate rows of simplex teeth on one sprocket
• Transfers drive - passes drive from one chain to another along a line of shafts
• Pilot bore - can be machined to fit the shaft exactly, with a keyway and set screw added
• Hub design - gives a solid mounting on the shaft
• Accurate chain spacing - both tooth rows are made together, so the chains stay correctly spaced
• Steel construction - strong and durable for industrial drives
• Range of sizes - available in many tooth counts and chain sizes

In simple terms, a double simplex sprocket is a sprocket with two separate tooth rows that drives two simplex chains from one shaft.

Why are double simplex sprockets essential?

Double simplex sprockets are essential because many machines need to drive more than one chain from the same shaft. Fitting two separate sprockets takes up more space, needs more fixings, and makes alignment harder. A double simplex sprocket combines both drives into one compact unit, keeping the two chains accurately spaced and aligned.

Their main benefits are:

• Compact drive - drives two chains from a single sprocket, saving space on the shaft
• Accurate alignment - both tooth rows are made together, so the chains run correctly spaced
• Flexible layouts - ideal for line shafts, roller conveyors, and multi-shaft drives
• 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
• Cost-effective - one sprocket replaces two, reducing parts and fitting time

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

• Roller conveyors - driving rollers in sequence, with chains linking one roller to the next
• Line shaft drives - passing drive along a series of shafts
• Agricultural machinery - drives on implements and processing equipment
• Packaging and food machinery - multi-chain drives on production lines
• Material handling - transfer systems and conveyors
• Industrial machinery - drives where one shaft powers two separate outputs

The main types of double simplex sprockets

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

By chain standard:

• British Standard (BS) double simplex sprockets - suit European-style simplex roller chains, such as 06B, 08B, 10B, and 12B
• ANSI double simplex sprockets - suit American-style simplex roller chains, such as 35, 40, 50, and 60

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

By chain size:

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

By number of teeth:

• Small sprockets - fewer teeth, used where space is limited or as drive sprockets
• Large sprockets - more teeth, used 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:

• Double simplex tapered bore sprockets - double simplex sprockets designed for tapered locking bushes
• Duplex sprockets - sprockets with two closely spaced tooth rows for double-strand duplex chain
• Simplex chain and links - chain and connecting links for each of the two drives

How to choose the right double simplex sprocket?

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

• Chain type - make sure each drive uses simplex chain. For a single duplex chain, choose a duplex sprocket instead
• Chain standard - check whether the drive uses British Standard or ANSI chain
• Chain size - choose a sprocket that matches the chain pitch exactly, such as 06B or 08B
• Number of teeth - choose a tooth count that gives the required ratio and fits the space. Larger sprockets give smoother running and less chain wear
• Chain spacing - check the spacing between the two tooth rows suits the layout of the drive and the sprockets it connects to
• 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 each drive
• Quality and brand - choose sprockets from reputable suppliers for accurate teeth and reliable performance

How to fit a double simplex sprocket

Fitting the sprocket correctly helps both chains 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 both rows of teeth line up with the sprockets they drive
• Secure the sprocket - tighten the set screw onto the key or shaft to stop the sprocket moving along the shaft
• Fit the chains - fit both chains and set the tension, leaving a small amount of slack on the slack side of each
• Check the drive - turn the drive by hand to check both chains run smoothly, then lubricate before running

FAQ - All you need to know about double simplex sprockets

What is a double simplex sprocket?

A double simplex sprocket has two separate rows of simplex teeth on one body, allowing it to drive two independent simplex chains at the same time.

What is the difference between double simplex and duplex sprockets?

A duplex sprocket has two closely spaced tooth rows for a single double-strand 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 double simplex sprocket with duplex chain?

No. Double simplex sprockets are designed for two separate simplex chains. Duplex chain needs a duplex sprocket.

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 are double simplex sprockets used for?

They are often used on roller conveyors and line shaft drives, where each sprocket receives drive from one chain and passes it to the next shaft with a second chain.

What does 08B mean?

08B is the British Standard chain size for 1/2 inch pitch chain. A double simplex sprocket marked 08B suits two 08B-1 simplex chains.

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 12 tooth drive sprocket and a 36 tooth driven sprocket give a 3:1 ratio.

Do double simplex sprockets need lubrication?

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

When should I replace the sprocket?

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