Drive chain: what 08B and 16A mean and how to get the pitch right

A roller chain code under ISO 606 is read like this. The first two digits are the pitch in sixteenths of an inch: 08 is 8/16, that is 1/2 inch, or 12.7 mm; 16 is one inch, 25.4 mm. The letter is the series: B is European, A is American. The digit after the hyphen is the number of strands: 08B-1 is single, 08B-2 is double. A and B chains with the same pitch are different chains: the roller or the width differs, and they have their own sprockets.

How to read the code

American chains are often written to the ANSI standard: 40, 50, 60, 80. Here the first digit is the pitch in eighths of an inch: 40 is 4/8, that is 1/2 inch. The zero at the end means a roller chain. The number of strands is written after a hyphen: 40-2 is a double strand.

The match follows from the pitch. Manufacturers state it directly for 40 = 08A and 80 = 16A.

European chains are made to ISO 606 and the German DIN 8187, American ones to ISO 606, ANSI B29.1 and DIN 8188.

Why 08A does not replace 08B

The pitch is the same, the rest is not. From the Tsubaki catalog:

08A and 08B have different rollers, so the sprocket teeth for them differ. 16A and 16B have the same roller, but 16B is wider by a millimeter or more. A chain that "almost fits" a sprocket wears faster and may jump off. That is why a request gives the series letter, not just the pitch.

How to find the pitch when the marking is not visible

Pitch is the distance between the centers of adjacent rollers. Measuring one link is inaccurate. Better this way:

1. Pull the chain taut.
2. Count several pitches in a row, for example ten.
3. Measure from the center of the first roller to the center of the last and divide by the number of pitches.
4. Compare with the series: 9.525 (06B), 12.7 (08), 15.875 (10), 19.05 (12), 25.4 (16), 31.75 (20) mm.

To tell series A from B, measure the roller diameter and the width between the inner plates and compare with the table above. For a double-strand chain you also need the transverse pitch between strands.

Elongation: when to replace the chain

Over time a chain "stretches": the pins and bushings wear and the pitch grows. Elongation is calculated as a percentage:

elongation = (measured length of N pitches − N × pitch) / (N × pitch) × 100%.

Example. Ten pitches of 08B chain should measure 127 mm. If you measure 129 mm, the elongation is about 1.6%.

Manufacturers' limits differ:

Measure on the taut run and at several places along the chain.

Sprockets

A new chain on worn sprockets lasts noticeably less. Renold advises inspecting the teeth before fitting a new chain and replacing the sprockets if they show wear. Tsubaki writes that replacing the chain in time protects the sprockets.

Signs of tooth wear: the tooth has become pointed, the profile has turned hook-shaped, the working face is worn into a groove.

For a sprocket the request needs: the chain code, the number of teeth, the bore and the way it seats on the shaft (bore, keyway), the hub on one side or both, and for a multi-strand sprocket the number of strands.

What to put in a chain request

1. The code: 08B-2, 16A-1 and so on. If it is not visible, the pitch, roller diameter and width between inner plates.
2. Length: number of links or length in meters.
3. Connecting link: spring clip, cotter pin, or offset link.
4. If the chain has attachment plates or extended pins, a photo and dimensions.
5. A photo of the old chain next to a ruler.

How we do it

• From the code or measurements we look for the chain and sprockets at the manufacturing plant.
• We send what we find before the order: standard series, pitch, roller, width, length and connecting link.
• At the plant we check the marking of the chain being shipped against the agreed item.

There are no chains or sprockets in the catalog at the moment: they are selected on request.