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### Double Square-Thread Power Screw Axial Linear Lifting Force Equations and Calculator

Double Square-Thread Power Screw Axial Linear Lifting Force Equations and Calculator

In general, when the screw is loaded axially, a thrust bearing or thrust collar may be used between the rotating and stationary links to carry the axial component.  Minor Diameter:
dr = d - p

Pitch (mean) diameter
dm = d - p/2

l = 2p

Torque required to rasie load up:  Overall efficiency: Where:

d = Major diameter (in, mm),
dr = Minor Diameter (in, mm),
dm = Pitch (mean) diameter (in, mm),
p = Pitch Diameter (in, mm),
µ - Coefficient of friction,
µc = Coefficient of collar friction,
dc = Mean collar diameter (in, mm),
F = External load on screw (lbsf, N)
Tr = Torque required to lower load (in-lbs, N-mm),
Tl = Torque required to lower load
e = Oveall efficiency

Reference:

Mechanical Engineering Handbook,
Edited by: Ban B. Manrghitu
Department of Mechanical Engineering, Auburn University,
Auburn, Alabama
2001