1. What is Screw Pull Out Strength?

The screw pull out strength is the maximum force required to pull a screw out of a material. It depends on the screw diameter, engagement length, and the shear strength of the material.

2. How Does the Calculator Work?

The calculator uses the screw pull out formula:

Where:

• \( F \) — Pull out force (N)
• \( d \) — Screw diameter (mm)
• \( L \) — Engagement length (mm)
• \( S \) — Material shear strength (MPa)

Explanation: The formula calculates the force required to shear the material along the cylindrical surface created by the screw threads.

3. Importance of Pull Out Strength Calculation

Details: Calculating pull out strength is crucial for ensuring mechanical fasteners will perform as intended under load, preventing failure in applications like construction, automotive, and aerospace.

4. Using the Calculator

Tips: Enter screw diameter in mm, engagement length in mm, and material shear strength in MPa. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What affects screw pull out strength?
A: Main factors are screw diameter, thread engagement length, material properties, thread design, and installation torque.

Q2: How accurate is this calculation?
A: It provides a theoretical maximum. Actual values may vary due to material imperfections, surface conditions, and dynamic loads.

Q3: What's typical shear strength for common materials?
A: Wood: 5-15 MPa, Aluminum: 100-200 MPa, Steel: 200-400 MPa, Plastics: 20-80 MPa (varies by specific material).

Q4: Should safety factors be applied?
A: Yes, for critical applications, divide the result by an appropriate safety factor (typically 2-5x depending on application).

Q5: Does thread pitch affect pull out strength?
A: Yes, but this simple formula doesn't account for it. Fine threads typically have slightly higher pull out strength than coarse threads.