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TB003 (Rev1) - Timing Belt and Sprocket Tooth Profiles
A large number of machine tools employ timing belts and sprockets to transfer motion of the servo motor shaft
to the ballscrew. This allows the machine tool builder to easily change the overall turns ratio of the axis drive
system, and allows the servo motor to be placed in a space efficient position.
The term "pitch", when used in association with timing belts and sprockets refers to the overall tooth size and
tooth spacing. Timing belts and sprockets come in different pitches and tooth profiles that cover a wide range
of power transmission requirements. Imperial or "inch" pitch timing belts and sprockets utilize a square tooth
design, while the metric pitch belts and sprockets use a rounded tooth profile. The most common pitches
utilized on machine tools are 3/8" (designated by the Letter code L) and metric 5mm or 8mm.
By far, the metric pitches offer better performance. The reason has to do with the different tooth profiles.
Imperial pitch belts use a square tooth design. As the belt wears and overall belt tension is reduced, the
possibility exists that the worn tooth may slip slightly in the sprocket groove, introducing lost motion into the
machine tool. The rounded tooth shape of the metric pitch belt and sprocket offers superior power
transmission efficiency and wear resistance. A properly tensioned metric pitch belt doesn't slip, even when the
belt is worn.
For best overall performance and wear resistance, use 5mm pitch belts and sprockets on your machine tool.
Use 8mm pitch on a very large machine tool. Two sources for these belts and sprockets are: Gates Rubber
Company HTD PowerGrip system (distributed by bearing houses world-wide), H. Neuman & Company,
Schiller Park, Il.. Voice #847-671-5885, Fax #671-3603.
Document History
Rev1 Created on 1997-10-01