Gearbox & Drivetrain · DWG LS-030

Sprocket & chain code decoder

Read an ANSI (ASME B29.1) or ISO 606 sprocket or chain number: pitch, standard, teeth and bore, plus pitch diameter p ÷ sin(180°/N), approximate OD and chain speed from RPM.

Maker method (Martin, Renold; ANSI B29.1 / ISO 606 numbering)Last reviewed

Source: Martin sprocket nomenclature (PDF) · Martin sprocket engineering data (PDF) · Renold roller chain designer guide (PDF)

Outside diameter is Martin’s approximation and varies with the cutter; bore marking conventions vary by manufacturer.

Sprocket / Chain Code
Try:
Fills in chain speed in ft/min and m/s.
How the code is read
  • ANSI (ASME B29.1) chain number: the right-hand digit is the chain type (0 = standard roller chain, 5 = rollerless bushing chain, 1 = lightweight chain such as No. 41); the digits to its left are the pitch in eighths of an inch. 40 = 4/8 = ½″; 160 = 16/8 = 2″.
  • Sprocket (Martin-style catalog number): optional strand prefix (D double, E triple, F quadruple, DS double-single), chain number, sprocket type (A plate / no hub, B hub one side, C hub both sides, D detachable hubs, BS bored-to-size, BTB taper-bushed), tooth count, optional H (hardened teeth) or SS (stainless), then the bore. Example: D160B16H 2¼.
  • ISO 606 chain number: the first two digits are the pitch in sixteenths of an inch (08 = 8/16 = ½″ = 12.7 mm); B = European (British) series, A = American-dimension series. An optional strand suffix (-1, -2, -3) follows. The sprocket form 08B-16T-25 is read as chain 08B, 16 teeth, 25 mm bore.
  • Pitch diameter PD = p ÷ sin(180°/N). Outside diameter OD ≈ p × (0.6 + cot(180°/N)) (Martin engineering data; actual OD depends on the cutter, so treat it as approximate, especially for ISO B-series sprockets).
  • Chain speed = N × p × RPM ÷ 12 ft/min (same as Martin’s T × RPM ÷ K, with K = pitches per foot).
  • Bore marking varies by maker. Some print a fraction (1, 1-1/4, 1 1/4), some decimals, some mm, and some leave a stock bore off the number entirely. A bore with no unit is read as inches for ANSI codes and mm for ISO codes. Check the hub stamp or the maker’s catalog before machining.

Sources: Martin roller chain sprocket nomenclature card (PDF) · Martin sprocket engineering data (PDF) · Renold roller chain designer guide (PDF) · U.S. Tsubaki general catalog (PDF) · ANSI/ASME B29.1 · ISO 606

Checking a worn chain? Measure elongation on the Chains tab of Component Life (chain wear check).