1. What is Screw Pull Out Strength?

The screw pull out strength is the maximum force required to pull a screw out of the material it's embedded in. It's an important factor in mechanical design and construction to ensure fasteners remain securely in place.

2. How Does the Calculator Work?

The calculator uses the screw pull out strength formula:

Where:

• \( F \) — Pull out force (N)
• \( d \) — Screw diameter (mm)
• \( L \) — Engagement length (mm)
• \( S \) — Shear strength of the material (MPa)

Explanation: The equation calculates the force required to shear the material along the cylindrical surface area created by the screw's engagement.

3. Importance of Pull Out Strength Calculation

Details: Accurate pull out strength estimation is crucial for ensuring mechanical fasteners can withstand operational loads without failing.

4. Using the Calculator

Tips: Enter screw diameter and 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, engagement length, material shear strength, thread design, and installation torque.

Q2: How accurate is this calculation?
A: It provides a theoretical maximum. Real-world 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: 10-50 MPa (varies by specific material).

Q4: Should safety factors be applied?
A: Yes, typical safety factors range from 2-5x depending on application criticality and load characteristics.

Q5: Does thread type affect pull out strength?
A: Yes, coarse threads generally have higher pull out strength in soft materials, while fine threads perform better in hard materials.