The Lifting Torque for a Leadscrew calculator computes the torque required to lift a load with a square thread power screw assembly.
INSTRUCTIONS: Choose units and enter the following:
Leadscrew Square Thread
- (L) Lead (linear distance the nut moves per full revolution)
- (F) Load
- (dm) Mean Thread Diameter
- (μ) Coefficient of Friction for Thread (Default: 0.2)
Lifting Torque (TR): The calculator returns the torque in Newton meters (N m). However, this can be converted to compatible units via the pull-down menu.
| Screw Metal | Nut Metal | |||
| Steel | Bronze | Brass | Cast Iron | |
| Dry Steel | 0.15-0.25 | 0.15-0.23 | 0.15-0.19 | 0.15-0.25 |
| Machine Oiled Steel | 0.11-0.17 | 0.10-0.16 | 0.10-0.15 | 0.11-0.17 |
| Bronze | 0.08-0.12 | 0.04-0.06 | N/A | 0.06-0.09 |
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The Math / Science
The Leadscrew Lifting Torque equation is:
`T_R= F*d_m/2((L+pi*μ*d_m)/ (pi*d_m- μ*L)) `
where:
- TR is the torque required to raise a load using a Square Thread Power Screw assembly.
- dm is the mean thread diameter
- dc is the mean collar diameter
- L is the lead
- F is the load
- μ is the coefficient of friction for thread
Leadscrews
A leadscrew is a mechanical device that converts rotational motion into linear motion. It consists of a threaded shaft and a mating nut that moves along the shaft when it is rotated. Leadscrews are commonly used in applications requiring precise linear movement, such as CNC machines, 3D printers, lathes, and linear actuators.
Key Features of a Leadscrew:
- Threaded Shaft: The screw has helical threads that engage with the nut.
- Nut: The component that moves along the shaft when it rotates.
- Linear Motion: Rotating the screw causes the nut to move in a straight line.
- High Precision: Often used in precision positioning applications.
Types of Leadscrews:
- Acme Leadscrew: Has a trapezoidal thread shape for strength and durability.
- Square Leadscrew: Provides high efficiency but is harder to manufacture.
- Ball Screw: Uses ball bearings to reduce friction, improving efficiency and longevity.
- Buttress Thread Leadscrew: Designed for heavy loads in one direction.
Advantages:
✔ Simple design
✔ Self-locking (in most cases, prevents backdriving)
✔ Precise control over motion
Disadvantages:
❌ Lower efficiency due to friction
❌ Limited speed compared to ball screws
