Measuring a roller chain is a two-step process which involves first determining the pitch size of the chain's roller pins and then calculating its actual length. The most common measurement system used to determine these numbers in the United States is the American National Standards Institute or ANSI.
The size of the machine which uses a roller chain, which might include anything from a motorcycle or bicycle to industrial equipment, affect its two units of measurement of pitch and length. Larger machines use larger pins and, generally, longer chains.
Step 1: Determining Pitch
In the ANSI system, the "pitch" of a roller chain is expressed in 1/8-inch increments, and refers specifically to the length between the center of one roller pin to the center of the next. Users can use any measurement tool to determine this length, and then must use a chart to convert that measurement to a number. For example, a 1/4-inch pitch translates to a number 25 pin See the table provided by maintenancetechnology in the "references" section for additional conversions.
Step 2: Determining Total Chain Length
Once users know the pin number associated with their roller chain, determining its total length is as simple as counting the number of roller pins contained within the chain itself. Users can either detach the chain or count the rollers while the chain is still connected to the machine. However, it is important to note that older machines with worn chains, especially motorcycles, may have been altered by previous owners in an attempt to readjust the chain and prevent the need for its replacement. Removal of one or two rollers in these cases is common according to sprocketsunlimited . In this situation, users should always purchase a new chain with additional rollers, just in case.