Load on Screw given Torque Required in Lifting Load with Trapezoidal Threaded Screw Calculator

Load on Screw Formula:

\[ W = \frac{Mt_{li} \times (1 - \mu \times \sec(0.2618) \times \tan(\alpha))}{0.5 \times d_{m} \times (\mu \times \sec(0.2618) + \tan(\alpha))} \]

Torque for lifting load:

N·m

Coefficient of friction:

Helix angle of screw:

Mean diameter of screw:

Load on screw:

1. What is Load on Screw Calculator?

Definition: This calculator determines the axial load that can be lifted by a trapezoidal threaded screw given the input torque, friction coefficient, helix angle, and mean diameter.

Purpose: It helps mechanical engineers and designers calculate the load capacity of power screws used in lifting applications.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ W = \frac{Mt_{li} \times (1 - \mu \times \sec(15°) \times \tan(\alpha))}{0.5 \times d_{m} \times (\mu \times \sec(15°) + \tan(\alpha))} \]

Where:

\( W \) — Load on screw (Newtons)
\( Mt_{li} \) — Torque for lifting load (N·m)
\( \mu \) — Coefficient of friction at screw thread (typically 0.15±5%)
\( \alpha \) — Helix angle of screw (degrees±5%)
\( d_{m} \) — Mean diameter of power screw (meters±5%)
\( \sec(15°) \) — Secant of 15° (approximately 1.033)

Explanation: The formula accounts for the torque required to overcome friction and lift the load in a trapezoidal threaded screw.

3. Importance of Load Calculation

Details: Proper load calculation ensures screw selection can handle required loads without failure while maintaining efficiency.

4. Using the Calculator

Tips: Enter torque in N·m, friction coefficient (default 0.15), helix angle in degrees (default 4.5°), and mean diameter in meters (default 0.046m). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical coefficient of friction for screw threads?
A: For well-lubricated steel screws, μ ≈ 0.15±5%. Dry conditions may increase this to 0.2-0.3.

Q2: How is helix angle determined?
A: Helix angle depends on thread pitch and diameter. For standard trapezoidal threads, it's typically 2-5°.

Q3: Why is 15° used in the secant function?
A: 15° is half the thread angle (30°) for standard trapezoidal threads, affecting the normal force calculation.

Q4: How accurate is this calculation?
A: Results are typically within ±5% of actual values, depending on manufacturing tolerances and lubrication.

Q5: What safety factor should I apply?
A: For lifting applications, a minimum safety factor of 5:1 is recommended for critical loads.