Roller chain drives are simple, efficient, and forgiving — until they are not. Most chain problems trace back to three decisions: the chain number, the sprocket tooth count, and how the drive is aligned. Get those right and a chain drive is one of the most reliable components in the plant.
Chain numbers and pitch
ANSI roller chain is identified by number: No. 35, 40, 50, 60, 80, 100, 120, 140, 160, 180, 200, and 240. The number relates to the pitch in eighths of an inch — No. 40 chain has a 4/8-inch (0.500-inch) pitch, No. 60 is 6/8-inch (0.750-inch), No. 80 is 1.000-inch. Pitch is the distance between pin centers, and it must match the sprocket tooth spacing exactly.
Choosing the chain number is a strength calculation: the working load of the drive must stay inside the chain's rated capacity with an appropriate service factor. When loads grow — a new, more aggressive conveyor or a heavier product line — the chain must be re-rated, not just replaced with the same number.
Sprocket selection
Stock sprockets come in standard configurations: Type A (plate), Type B (hub on one side), Type C (hub on both sides), and Type D (split hub). Boring options include finished bore, QD, taper bushed, and MST bushed styles so one stock sprocket can fit a range of shaft diameters.
Sprocket part numbers follow a consistent pattern: the chain pitch is written to the left of the hub-style code, followed by the number of teeth. A multiple-strand drive adds a prefix letter for the strand count, and an H suffix means the teeth are heat treated for extra wear life. For example, a 60B17-style number reads as No. 60 chain, B hub style, 17 teeth.
Tooth count matters beyond ratio: small sprockets (under 17–20 teeth on most stock sizes) run with more chordal action and vibration, and the catalog lists minimum recommended tooth counts by chain number. Where space allows, a larger sprocket set gives smoother operation and longer chain life.
Alignment and maintenance
Sprockets must be aligned with the shaft axes parallel. A quick field check: lay a straight edge across the faces of both sprockets, or use a string between the outside faces — the faces should contact the string at every point. Misaligned drives wear the inside of the link plates and one side of the sprocket teeth.
Chain wear shows up as elongation and as visible wear on the link plates and rollers. The maintenance guides recommend replacing a chain once 5% or more of the link-plate height is worn away, and before elongation lets the chain ride up on the sprocket teeth — past that point the chain skips and starts damaging the sprockets. Check for tight joints, turned pins, and battered link plates at the same inspection.
Stock what you run
RBC Industrial stocks ANSI roller chain across the common numbers and Martin sprockets in finished-bore, QD, taper-bushed, and MST styles — plus engineering-class, idler, and conveyor sprockets. If your drive uses a stock number, we can usually match it from the shelf.