guide
chain sizes
The first digit of the size is the pitch, the distance between rollers, in eighths of an inch: 4 means 1/2 inch (12.7 mm) and 5 means 5/8 inch (15.875 mm). The other digits stand for the width.
- 01
415, 420 and 428 are 1/2 inch chains; 520, 525 and 530 are 5/8 inch chains. A 428 chain is about 7.9 mm wide inside; a 420 chain about 6.4 mm.
- 02
The chain and both sprockets must all be the same size. A chain cannot run on a sprocket of another pitch, and a different width does not seat properly.
- 03
An odd number of links needs an offset (half) link. Kits normally use an even number.
Source: ANSI/ASME B29.1 and ISO 606 roller chain series (1/2 in and 5/8 in pitch)