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For background discussion on this topic see the earlier section on critical speedlink

Screw critical speed (maximum RPM) calculation
A screw assembly has a maximum RPM which it should operate.  For Inch screws the critical speed can be calculated using the following formula:

nc = Cs x 4.76 x 106 x dr/L2

nc = Critical speed [RPM]
dr = Root diameter of the screw [in]
L = Unsupported length or length between the bearings [in]
Cs = End Fixity Factor.  See table below

It is recommended to operate below 80% of the screw critical speed.

End fixity factor - critical speed

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