Coefficient of Friction of Screw given Effort for Trapezoidal Threaded Screw Calculator

Coefficient of Friction Formula:

\[ \mu = \frac{P_{li} - (W \times \tan(\alpha))}{\sec(0.2618) \times (W + P_{li} \times \tan(\alpha))} \]

Effort in lifting load:

Load on screw:

Helix angle of screw:

rad

Tolerance:

Coefficient of friction at screw thread:

1. What is Coefficient of Friction of Screw?

Definition: This calculator determines the coefficient of friction for trapezoidal threaded screws based on the effort required to lift a load.

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

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \mu = \frac{P_{li} - (W \times \tan(\alpha))}{\sec(0.2618) \times (W + P_{li} \times \tan(\alpha))} \]

Where:

\( \mu \) — Coefficient of friction at screw thread
\( P_{li} \) — Effort in lifting load (N)
\( W \) — Load on screw (N)
\( \alpha \) — Helix angle of screw (radians)
0.2618 — 15° converted to radians (trapezoidal thread angle)

Explanation: The formula accounts for the mechanical advantage and friction in trapezoidal screw threads.

3. Importance of Friction Coefficient Calculation

Details: Proper friction coefficient estimation ensures accurate screw design, predicts torque requirements, and evaluates efficiency.

4. Using the Calculator

Tips: Enter the effort (N), load (N), helix angle (radians), and optional tolerance (±5%). All values must be > 0 except tolerance.

5. Frequently Asked Questions (FAQ)

Q1: Why is the angle 0.2618 radians fixed in the formula?
A: This represents 15° which is standard for trapezoidal thread profiles.

Q2: What's a typical coefficient range for screw threads?
A: Typically 0.1-0.3 for well-lubricated steel screws, but can vary with materials and lubrication.

Q3: When would I use the tolerance field?
A: To account for manufacturing variations or experimental uncertainty (±5% is common).

Q4: How do I convert degrees to radians?
A: Multiply degrees by π/180 (e.g., 5° = 5 × π/180 ≈ 0.0873 rad).

Q5: Does this apply to other thread types?
A: This formula is specific to trapezoidal threads. Other profiles require different calculations.