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Keyway Stresses for Non-metallic Gears and Shafts Formulas and Calculator

Machine Design and Engineering
Mechanical Gear Design and Engineering

Keyway Stresses for Non-metallic (phenolic laminated materials ) Gears Formulas and Calculator

The keyway stress is calculated by the formulas:

Imperial Units

S = ( 33,000 · HP ) / ( V ·  A )

SI Units

S = ( 1,000 ·  KW ) / ( V · A )

For keyway stresses expressed in terms of shaft radius r inches and revolutions per minute

S = ( 63,000 · HP ) / ( rpm · r · A )

For keyway stresses expressed in terms of shaft radius r meter and revolutions per minute

S = ( 9,550 ·  KW ) / ( rpm ·  r ·  A )

When the design is such that the keyway stresses exceed 3000 psi (20.68 MPa), metal reinforcing end plates may be used. Such end plates should not extend beyond the root diameter of the teeth. The distance from the outer edge of the retaining bolt to the root diameter of the teeth shall not be less than a full tooth depth. The use of drive keys should be avoided, but if required, metal end plates should be used on the pinion to take the wedging action of the key.

For phenolic laminated pinions, the face of the mating gear should be the same or slightly greater than the pinion face.


S = unit stress in psi (Pa)
HP = horsepower transmitted
KW = kilowatt power transmitted
V = peripheral speed of shaft in Ft/min (m/sec)
A = square inch (square meter) area of keyway in pinion (length × height)
rpm = revolutions per minute


Machinery's Handbook, 29th Edition

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