Simplex Links

What are simplex links?

Simplex links are connecting and repair links used to join, shorten, or repair simplex roller chain. Simplex chain has a single row of rollers and is the most widely used type of roller chain, found on everything from light-duty machinery, bicycles, and garden equipment to industrial conveyors and drives. Because roller chain is supplied in lengths and needs to be joined into a continuous loop, connecting links are used to close the chain, while other links are used to adjust the chain length or replace damaged sections.

Simplex links are made to match the pitch, roller size, and inner width of the chain exactly, so the joined chain runs smoothly over the sprockets and carries its full load.

A typical simplex connecting link has:

• Outer plates - the side plates that hold the link together and connect to the inner links of the chain
• Pins - two pins that pass through the chain, usually fixed into one outer plate
• Removable side plate - the loose plate fitted over the pin ends to close the link
• Fastener - a spring clip, split pins, or rivets that hold the removable plate in place

Simplex links are usually described by:

• Chain size - such as 06B-1, 08B-1, 10B-1, or 12B-1 for British Standard chain, or 25-1, 35-1, 40-1, or 50-1 for ANSI chain. The 1 shows it is simplex
• Chain standard - British Standard (BS) or American Standard (ANSI)
• Pitch - the distance between the centres of adjacent pins, such as 1/4 inch, 3/8 inch, 1/2 inch, or 5/8 inch
• Pitch and inner width - some chains, such as cycle and light-duty chains, are described by pitch and inner width, such as 1/2 × 3/16 inch
• Link type - often identified by a number, such as Nr. 26 for a connecting link with a spring clip, Nr. 11 for a cottered connecting link, or Nr. 30 for a double cranked link

For example, an 06B-1 Nr. 26 simplex connecting link joins 3/8 inch pitch British Standard simplex chain and is secured with a spring clip.

Key features:

• Joins chain into a loop - closes simplex chain around the sprockets
• Matches the chain exactly - made to the same pitch, roller size, and width as the chain
• Quick fitting - spring clip links can be fitted and removed with simple tools
• Repairs damaged chain - replace worn or broken sections without replacing the whole chain
• Adjusts chain length - cranked links allow an odd number of links where needed
• Wide range of sizes - from small chains for light mechanisms to larger industrial chains
• BS, ANSI, and cycle sizes - to suit British Standard, American Standard, and light-duty chains

In simple terms, simplex links are the connecting and repair links that join simplex roller chain into a strong, continuous loop.

Why are simplex links essential?

Simplex links are essential because every roller chain drive needs a reliable way to join the chain, and chains often need repairing or adjusting during their working life. Simplex chain is used on a huge variety of machines, so having the correct connecting link on hand makes it quick and easy to fit new chain, repair breakages, and get equipment back to work. Using the wrong link, or fitting it incorrectly, can cause the chain to come apart, damage sprockets, and stop the machine.

Their main benefits are:

• Secure chain joining - closes the chain loop safely and reliably
• Quick installation - chains can be fitted and removed without special equipment
• Easy repairs - broken or damaged links can be replaced quickly, reducing downtime
• Length adjustment - allows chains to be shortened or adjusted to suit the drive
• Full compatibility - matched to the chain for smooth running over sprockets
• Convenient maintenance - makes it easy to remove chains for cleaning and inspection
• Cost-effective - repairing chain is often cheaper than replacing it

Simplex links are used across a wide range of industries and applications, including:

• Industrial drives - light and medium-duty chain drives on machinery
• Conveyors - conveyor drives and transfer systems
• Agricultural machinery - drives on implements, drills, balers, and harvesters
• Garden machinery - drives on mowers, cultivators, and other equipment
• Packaging and food machinery - drive and timing systems on production lines
• Bicycles, BMX, and leisure vehicles - chain drives on cycles, karts, and similar equipment
• Doors, gates, and lifting equipment - chain-driven openers and mechanisms
• Maintenance and repair - replacing and adjusting chain on existing drives

The main types of simplex links

Simplex links are usually grouped by their design and the chain standard they suit.

By link type:

• Connecting links with spring clip - often referred to as Nr. 26 links. The removable side plate is held in place with a spring clip, allowing quick fitting and removal. The most widely used type of simplex connecting link
• Cottered connecting links - often referred to as Nr. 11 links. The removable side plate is held with split pins, giving a secure joint for larger chains and heavier drives
• Riveting connecting links - the pins are riveted over after fitting, giving a strong, permanent joint for high speeds and heavy loads
• Cranked links (offset links) - allow a chain to have an odd number of links. Cranked links reduce chain strength, so they should only be used when necessary
• Double cranked links - often referred to as Nr. 30 links, these combine a cranked link with an inner link to give a two-pitch offset section, allowing an odd number of links while giving a stronger option than a single cranked link
• Inner links - the roller links between connecting links, used for repairs

By chain standard:

• British Standard (BS) simplex links - suit European-style roller chains, such as 05B-1, 06B-1, 08B-1, 10B-1, 12B-1, and 16B-1
• ANSI simplex links - suit American-style roller chains, such as 25-1, 35-1, 40-1, 50-1, 60-1, and 80-1
• Cycle and light-duty links - suit chains described by pitch and inner width, such as 1/2 × 1/8 inch and 1/2 × 3/16 inch

British Standard and ANSI chains of the same pitch are not interchangeable, as their roller diameters, inner widths, and plate dimensions are different.

Common pitches:

• 1/4 inch - such as ANSI 25-1
• 3/8 inch - such as 06B-1 and ANSI 35-1
• 1/2 inch - such as 08B-1, ANSI 40-1, and 1/2 inch cycle chains
• 5/8 inch - such as 10B-1 and ANSI 50-1
• 3/4 inch - such as 12B-1 and ANSI 60-1
• 1 inch - such as 16B-1 and ANSI 80-1

How to choose the right simplex links?

Choosing the right simplex link means matching it exactly to the chain. Work through these points in order:

• Chain standard - check whether the chain is British Standard, ANSI, or a cycle or light-duty chain. This is often stamped on the chain plates
• Chain size - match the chain size, such as 06B-1 or 40-1
• Number of strands - make sure the link is simplex, to match a single-strand chain
• Pitch - check the pitch by measuring the distance between the centres of adjacent pins
• Inner width - for cycle and light-duty chains, check the inner width between the inner plates, such as 1/8 inch or 3/16 inch
• Link type - choose a connecting link to join the chain, a cranked or double cranked link if you need an odd number of links, or inner links for repairs
• Fastening method - choose spring clip links for quick fitting on most drives, cottered links for heavier drives, or riveting links for high speeds and heavy loads
• Load and speed - for high speeds and heavy loads, consider cottered or riveting links, and avoid cranked links where possible
• Material and finish - choose links that match the chain material and finish, such as standard steel, nickel plated, or stainless steel
• Quality and brand - choose links from reputable suppliers that match the chain manufacturer’s quality

How to fit a simplex connecting link

Fitting a connecting link correctly is important for safety and reliability:

• Isolate the drive - switch off and isolate the machine before working on the chain
• Prepare the chain - wrap the chain around the sprockets so the two ends meet, using a chain puller if needed to hold them together
• Insert the link - push the pins of the connecting link through the two end rollers of the chain from the back
• Fit the plate - fit the removable side plate over the pin ends, pressing it fully into place
• Fit the fastener - fit the spring clip, insert and bend the split pins, or rivet the pins, depending on the link type
• Check the spring clip direction - fit the spring clip so its closed end faces the direction of chain travel, reducing the risk of it catching and coming off
• Check the joint - make sure the link moves freely and is fully secured
• Set the tension - adjust the chain tension, then turn the drive by hand to check it runs smoothly

FAQ - All you need to know about simplex links

What is a simplex link?

A simplex link is a connecting or repair link designed for simplex roller chain, which has a single row of rollers.

What does Nr. 26 mean?

Nr. 26 usually refers to a connecting link with a spring clip, used to join roller chain into a loop.

What does Nr. 30 mean?

Nr. 30 usually refers to a double cranked link, also called a double offset link. It allows a chain to have an odd number of links while being stronger than a single cranked link.

What does the 1 in 06B-1 mean?

The 1 shows the chain is simplex, with a single strand. For example, 06B-1 is simplex, 06B-2 is duplex, and 06B-3 is triplex.

What does 1/2 × 3/16 inch mean?

This describes a chain by its pitch and inner width. A 1/2 × 3/16 inch chain has a 1/2 inch pitch and a 3/16 inch gap between the inner plates. These sizes are common on cycle, BMX, and light-duty chains.

What is the difference between BS and ANSI chain links?

BS links suit British Standard roller chain, and ANSI links suit American Standard roller chain. They have different dimensions, even at the same pitch, and are not interchangeable.

How do I know which chain I have?

Check the markings on the chain plates, which often show the size and standard. If there are no markings, measure the pitch, roller diameter, and inner width, and compare them with a chain chart.

What is a cranked link?

A cranked link, also known as an offset link, allows a chain to have an odd number of links. It is weaker than standard links, so it should only be used when an odd number of links is unavoidable.

Which way should the spring clip face?

The closed end of the spring clip should face the direction of chain travel. This helps stop the clip catching on anything and coming off.

Can I reuse a connecting link?

It is best to fit a new connecting link. Spring clips and split pins can weaken once removed, and worn links can fail.

Can I join new chain to old chain?

It is not recommended. Old chain will have stretched through wear, and mixing it with new chain can cause poor running, noise, and rapid wear on the sprockets.