British Standard Chain Numbering
BS chains are measured in 16ths of an inch. For chains 06B and larger, the pitch can be found from dividing the chain number by 16 i.e.
06B Chain Pitch (mm) = 06/16 × 25.4 = 9.525mm
A hyphenated number after the initial chain number indicates the number of chain strands. For example, 24B-1 is a single strand, 24B-2 is two strands and 24B-3 is three strands.
ANSI Chain Numbering
ANSI chains are measured in 8ths of an inch, but the right-hand digit of the chain code also designates if the chain is standard (0), lightweight (1) or rollerless (5).
For example, a 41 chain would be a lightweight chain with a 4/8” pitch while 100 chain would be standard, having a pitch of 10/8”.
‘H’ after the chain number designates the chain as ‘Heavy’, adding an extra 1/32” to the thickness of the standard link plate. For example, a 100H chain would have a 4.8mm thick link plate instead of the standard 4mm thick plate.
A hyphenated number after the initial chain number indicates the number of chain strands. For example, 100-1 is a single strand, 100-2 is two strands, 100-3 is three strands and 100H-2 is heavy duty 100 series chain with 2 strands.
ANSI Roller Chain Proportions
ANSI roller chains have major dimensions that are roughly proportional to the chain pitch. These proportions were obtained through research and experimentation and are used for chains that conform to ASME B29.1;
Roller width ≈ 5/8 of the pitch.
Chain (roller) width ≈ 5/8 of the pitch.
Pin diameter ≈ 5/16 of the pitch.
Link plate thickness ≈ 1/8 of the pitch.
Maximum roller link plate height ≈ 0.95 × pitch.
Maximum pin link plate height ≈ 0.82 × pitch.