Power Screw Calculator
Analyze power screws (lead screws, jack screws). Calculate raising and lowering torque, efficiency, and self-locking condition.
Inputs
lb
in
in
in
Results
Raising Torque
1,517.6 in·lb
Lowering Torque
1,110.7 in·lb
Self-Locking
1
Screw Efficiency13.1%
Lead Angle3.04°
How to Use This Calculator
- Enter the Axial Load (W) in lb — the weight or force the screw must raise or lower.
- Enter the Mean Thread Diameter (dm) in inches — the average of major and minor diameters.
- Enter the Lead (l) in inches — the axial travel per revolution. For single-start threads, lead equals pitch.
- Set Thread Friction (f) and Collar Friction (fc): dry steel ≈ 0.15–0.25, lubricated ≈ 0.08–0.12.
- Enter the Mean Collar Diameter (dc) in inches where the thrust load is transferred.
- Review Raising Torque and Lowering Torque in in·lb, Screw Efficiency %, and whether the screw is Self-Locking — a non-self-locking screw requires a brake to hold load.
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