Ball Screw Back-Drive Torque Calculator
Estimate back-drive torque and holding torque from axial load, screw lead, and screw efficiency. The result is a preliminary engineering estimate, not a product rating or safety approval.
Calculate the documented engineering estimate
Enter the measured or assumed inputs in one unit system. The calculator converts to SI internally, evaluates the stated model, and displays the result in the selected unit system.
Engineering visualizer
Schematic, not to scale. The drawing updates from the production calculation engine and labels the main outputs.
Calculator by FIRGELLI Automations.
What This Calculator Calculates
What does ball screw back-drive torque mean? This quantity describes one specific part of the actuator design problem. It should be read as a model output, not as a complete product selection rule.
When To Use This Calculator
When should I use the ball screw back-drive torque calculator? Use this section to connect the calculation to real actuator layouts, such as long cables, screw spans, synchronized axes, or position budgets. The example identifies the inputs that matter and the remaining checks.
How To Interpret The Results
How should I interpret the ball screw back-drive torque result? A larger result means the checked effect is becoming more important and should be compared with product data, mounting limits, or the next design check. A smaller result does not prove the whole system is safe.
When Not To Use This Calculator
When should I not use the ball screw back-drive torque model? Do not use this model when the inputs are unknown, the mechanism is outside the stated boundary, or the decision depends on manufacturer ratings, fatigue, shock, compliance, or regulated safety approval.
Real-World Engineering Examples
Where is ball screw back-drive torque used in real applications? Use this section to connect the calculation to real actuator layouts, such as long cables, screw spans, synchronized axes, or position budgets. The example identifies the inputs that matter and the remaining checks.
Causes, Effects, And Prevention
What problem leads someone to check ball screw back-drive torque? This calculation is often prompted by a symptom: slow motion, whip, skew, drift, repeatability error, heat, or a mismatch between expected and observed actuator behavior.
What design changes improve the ball screw back-drive torque result? The practical design response is to reduce the root cause, improve the boundary condition, shorten the unsupported path, add feedback, reduce resistance, or select a component whose published data fits the result.
Related Terms Engineers Compare
What related terms are confused with ball screw back-drive torque? The comparison clarifies similar terms so the user does not apply the right equation to the wrong problem.
Engineering model and calculation details
Estimate back-drive torque and holding torque from axial load, screw lead, and screw efficiency.
The page separates the calculator result from product selection. It explains the inputs, limitations, interpretation, and next design checks so the result is not mistaken for a complete actuator rating.
Governing equations
| Quantity | Equation | Model meaning |
|---|---|---|
| Idealized back-drive torque | T_back = F lead eta/(2pi) |
Calculates idealized back-drive torque for the stated simplified model. |
| Idealized holding torque without brake margin | T_hold = F lead/(2pi eta) |
Calculates idealized holding torque without brake margin for the stated simplified model. |
Variables and canonical units
| Symbol | Variable | SI unit | Domain |
|---|---|---|---|
axial_load |
Axial load | N | finite engineering value in the documented model domain |
screw_lead |
Screw lead per revolution | m | finite engineering value in the documented model domain |
screw_efficiency |
Screw efficiency | 1 | finite engineering value in the documented model domain |
backdrive_torque |
Idealized back-drive torque | N_m | finite result from valid inputs |
holding_torque |
Idealized holding torque without brake margin | N_m | finite result from valid inputs |
Assumptions and boundary conditions
- Inputs represent one consistent operating condition.
- The model uses the simplified boundary stated on the page.
- The model begins and ends at the user-defined actuator or mechanism boundary.
Limitations and omitted checks
- The result depends on user-entered values and simplified boundary conditions.
- The model does not replace FIRGELLI product data, installation review, endurance testing, or a qualified engineering review.
- Shock, fatigue, misalignment, mounting strength, and controller behavior may govern before the calculated value.
Worked example using the default inputs
The default inputs show the substitution path and provide a known-answer check for the displayed outputs.
| Stage | Substitution or result |
|---|---|
| Idealized back-drive torque | T_back = F lead eta/(2pi) |
| Idealized holding torque without brake margin | T_hold = F lead/(2pi eta) |
Interpretation: Use the result to decide whether the design needs a deeper product, mounting, electrical, thermal, or motion-control check.
What this model evaluates
| Mode or effect | Status | Disclosure |
|---|---|---|
| calculated quantity | evaluated | The named output is evaluated for the stated model. |
| manufacturer rating | not evaluated | The result is not a manufacturer product rating. |
| installation detail | not evaluated | Mounting, alignment, shock, fatigue, and environment require separate review. |
Common mistakes
- Treating a simplified estimate as a manufacturer rating.
- Mixing units or entering values measured at a different operating point.
- Ignoring mounting, alignment, shock, duty cycle, or controller limitations.
- Failing to compare the result with the next logical FIRGELLI design check.
Embed this calculator
The responsive iframe opens the calculator-only view without Shopify navigation or footer. FIRGELLI attribution, the visualizer, and calculation-error reporting remain available.
Engineering references
- National Institute of Standards and Technology. NIST Guide to the SI. National Institute of Standards and Technology, Accessed 2026. Supports: SI unit definitions and unit-consistent engineering calculation display.. Accessed 2026-07-28. Source.
- Barry N. Taylor and Chris E. Kuyatt. Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results. National Institute of Standards and Technology, NIST Technical Note 1297. Supports: Root-sum-square treatment of independent standard uncertainty components.. Accessed 2026-07-28. Source.
- OpenStax. University Physics Volume 1 - Motion Along a Straight Line. Rice University, 2016. Supports: Position change from speed and time used for drift accumulation.. Accessed 2026-07-28. Source.
Questions engineers ask about this model
How do I calculate ball screw back-drive torque?
Use the calculator when the listed inputs are known and the geometry matches the stated boundary. It returns the named result and shows the substitution path so the user can check the numbers. See Calculator.
What does ball screw back-drive torque mean?
This quantity describes one specific part of the actuator design problem. It should be read as a model output, not as a complete product selection rule. See What This Calculator Calculates.
When should I use the ball screw back-drive torque calculator?
Use this section to connect the calculation to real actuator layouts, such as long cables, screw spans, synchronized axes, or position budgets. The example identifies the inputs that matter and the remaining checks. See When To Use This Calculator.
How should I interpret the ball screw back-drive torque result?
A larger result means the checked effect is becoming more important and should be compared with product data, mounting limits, or the next design check. A smaller result does not prove the whole system is safe. See How To Interpret The Results.
When should I not use the ball screw back-drive torque model?
Do not use this model when the inputs are unknown, the mechanism is outside the stated boundary, or the decision depends on manufacturer ratings, fatigue, shock, compliance, or regulated safety approval. See When Not To Use This Calculator.
Where is ball screw back-drive torque used in real applications?
Use this section to connect the calculation to real actuator layouts, such as long cables, screw spans, synchronized axes, or position budgets. The example identifies the inputs that matter and the remaining checks. See Real-World Engineering Examples.
What problem leads someone to check ball screw back-drive torque?
This calculation is often prompted by a symptom: slow motion, whip, skew, drift, repeatability error, heat, or a mismatch between expected and observed actuator behavior. See Causes, Effects, And Prevention.
What design changes improve the ball screw back-drive torque result?
The practical design response is to reduce the root cause, improve the boundary condition, shorten the unsupported path, add feedback, reduce resistance, or select a component whose published data fits the result. See Causes, Effects, And Prevention.
What related terms are confused with ball screw back-drive torque?
The comparison clarifies similar terms so the user does not apply the right equation to the wrong problem. See Related Terms Engineers Compare.
What should I check after calculating ball screw back-drive torque?
After this calculation, check the adjacent FIRGELLI resource that evaluates the next likely constraint, such as product force, mounting, power, travel timing, or feedback control. See Related FIRGELLI Engineering Resources.
Author, validation, and review status
Author: Robbie Dickson
Author profile: Robbie Dickson prepares FIRGELLI actuator education and calculator content for product users and engineering teams. This draft requires manual engineering review.
Draft revision date: July 28, 2026
Engineering model type: Ball screw load to back-drive and holding torque estimate
Validation: The production JavaScript engine is compared with a separately written Python oracle across known-answer, SI/imperial-equivalent, boundary, invalid-input, and randomized cases.
Draft review status: Prepared as a FIRGELLI calculator expansion draft for manual engineering review.
