Coefficient of Friction of Screw given Torque Required in Lifting Load with Trapezoidal Thread Calculator

Coefficient of Friction Formula:

\[ μ = \frac{2 \cdot M_{tli} - W \cdot d_m \cdot \tan(\alpha)}{\sec(0.2618) \cdot (W \cdot d_m + 2 \cdot M_{tli} \cdot \tan(\alpha))} \]

Torque for lifting load:

N·m

Load on screw:

Mean Diameter of Power Screw:

Helix angle of screw:

rad

Coefficient of friction at screw thread:

1. What is Coefficient of Friction of Screw?

Definition: This calculator determines the coefficient of friction for a screw with trapezoidal thread when lifting a load, based on the required torque.

Purpose: It helps mechanical engineers and designers analyze screw thread performance and efficiency.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ μ = \frac{2 \cdot M_{tli} - W \cdot d_m \cdot \tan(\alpha)}{\sec(0.2618) \cdot (W \cdot d_m + 2 \cdot M_{tli} \cdot \tan(\alpha))} \]

Where:

\( μ \) — Coefficient of friction at screw thread
\( M_{tli} \) — Torque for lifting load (N·m)
\( W \) — Load on screw (N)
\( d_m \) — Mean Diameter of Power Screw (m)
\( \alpha \) — Helix angle of screw (rad)

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

3. Importance of Friction Coefficient Calculation

Details: Proper friction coefficient estimation ensures accurate torque requirements, screw efficiency calculations, and prevents mechanical failures.

4. Using the Calculator

Tips: Enter the torque, load, mean diameter, and helix angle. All values must be > 0. Results are accurate within ±5%.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical coefficient of friction for screw threads?
A: For dry steel-on-steel, it's typically 0.15-0.25, but varies with lubrication and materials.

Q2: Why is the angle 0.2618 radians in the secant function?
A: This represents 15°, a common thread angle component for trapezoidal threads.

Q3: How does helix angle affect the friction coefficient?
A: Higher helix angles generally reduce the effective friction coefficient for lifting.

Q4: Can this calculator be used for other thread types?
A: It's specifically designed for trapezoidal threads due to the 15° angle in the formula.

Q5: How accurate are the results?
A: Results are theoretically accurate within ±5% when input values are precise.