Coefficient of Friction of Power Screw given Effort in Moving Load with Acme Threaded Screw Calculator

Coefficient of Friction Formula:

\[ \mu = \frac{P_{li} - W \cdot \tan(\alpha)}{\sec(14.5^\circ) \cdot (W + P_{li} \cdot \tan(\alpha))} \]

Effort in lifting load (P_li):

Load on screw (W):

Helix angle of screw (α):

rad

Tolerance:

Coefficient of friction (μ):

1. What is Coefficient of Friction in Power Screws?

Definition: The coefficient of friction (μ) in power screws represents the ratio of frictional force to normal force between the screw threads and nut.

Purpose: It helps determine the efficiency and force requirements for Acme threaded screws used in lifting applications.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \mu = \frac{P_{li} - W \cdot \tan(\alpha)}{\sec(14.5^\circ) \cdot (W + P_{li} \cdot \tan(\alpha))} \]

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)
14.5° — Standard thread angle for Acme threads

3. Importance of Friction Calculation

Details: Proper friction calculation ensures accurate determination of screw efficiency, self-locking capability, and required driving torque.

4. Using the Calculator

Tips:

Enter effort in Newtons (N)
Enter load in Newtons (N)
Enter helix angle in radians
Set tolerance percentage (default ±5%)
All values must be positive

5. Frequently Asked Questions (FAQ)

Q1: Why is the thread angle fixed at 14.5°?
A: This calculator is specifically for Acme threads which have a standard included angle of 29° (14.5° per side).

Q2: How do I convert degrees to radians for the helix angle?
A: Multiply degrees by π/180 (or use our Angle Conversion Calculator).

Q3: What's a typical coefficient range for power screws?
A: Typically 0.1-0.3 for well-lubricated steel screws, but can vary with materials and lubrication.

Q4: What does the tolerance percentage represent?
A: It shows the acceptable variation range (±%) around the calculated coefficient value.

Q5: When would I need this calculation?
A: When designing or analyzing screw jacks, lead screws, or other power screw applications.