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Sprocket Nomenclature & Sprocket Types

All sprockets have unique industry numbers that represent the sprocket itself. There are several types of sprockets, and each type is usually designated with letters. A "types" of sprocket is simply the configuration of the sprocket. Most sprocket item/industry numbers usually represent the chain size, tooth count, bore size & type. Below is a listing of all types with sample item/industry numbers that breakdown the nomenclature.

Sprocket Types

  1. Type A

    Type A Sprocket

    Type A sprockets are a flat hubless roller chain sprocket with a minimum plain bore. These are commonly referred to as "plate sprockets". The Type A sprockets are commonly used for mounting onto hubs, flanges or welding to shafts.

    Example Item Number: 80A20
    • 80 = The Roller Chain Size - #80
    • A = Type Of Sprocket - Flat Sprocket (Hubless)
    • 20 = Number Of Teeth
  2. Type B

    Type B Sprocket

    Type B/BS sprockets have an extended hub on one side of the sprocket. These sprockets are offered in a plain bore or finished bore. Plain bore Type B sprockets have a MPB (Minimum Plain Bore), which are used for re-boring. Finished bore sprockets are bored to size and have a keyway with 2 setscrews.

    Example Item Number: 40B20-1 Or 40BS20-1
    • 40 = The Roller Chain Size - #40
    • B or BS = Type Of Sprocket - Sprocket With A Hub
    • 20 = Number Of Teeth
    • 1 = 1" Bore
  3. Type BB

    Type BB Sprockets

    Type BB sprockets is a sprocket with a sealed ball bearing, which is commonly referred to as an idler sprocket. The Type BB sprockets are used for taking up slack in long running lengths of roller chain. These can be mounted on a tensioner arm or mounted in a fixed position.

    Example Item Number: 50BB13-5/8
    • 50 = The Roller Chain Size - #50
    • BB = Type Of Sprocket - Sprocket With Bearing (Idler Sprocket)
    • 13 = Number Of Teeth
    • 5/8 = 5/8" Bore
  4. Type X

    X Series Sprocket Type

    Type X sprockets are known as weld on sprockets. These are the exact same as the Type "A" sprockets except X series sprockets have a 2" bore. All x series sprockets are compatible with any X series weld on hubs, which are available on a wide range of bore styles.

    Example Item Number: 4080X
    • 40 = The Roller Chain Size - #40
    • 80 = Number Of Teeth
    • X = Type Of Weld On Sprocket - X Series
  5. Type QD

    QD Sprocket Type

    QD (Quick Disconnect) sprockets is a specialty style sprocket where a hub is bolted into the sprocket. The QD hubs have an increased holding power to the shaft, which is achieved by the split and taper in the hub & torquing of the bolts. QD sprockets & hubs allow for easier assembly and disassembly.

    Example Item Number: 40SDS42
    • 40 = The Roller Chain Size - #40
    • SDS = Series Of QD Sprocket - Only Accepts SDS Hubs
    • 42 = Number Of Teeth

There are a few more other styles, but these are the most commonly used sprockets in the power transmission industry.