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How to Use Using Self-Tapping Screws in Plastic Without Cracking
Easylink Technical Insights
Last Updated: September 8, 2026
Table of Contents
How to Use Using Self-Tapping Screws in Plastic Without Cracking
Why Plastic Cracks When a Screw Goes In
Hoop Stress Explained
Common Causes of Cracking
Why Plastic Behaves Differently from Metal
Thread-Forming and Thread-Cutting Screws Behave Differently
What Makes a Thread "Plastic-Friendly"
Designing a Boss That Can Take the Load
Give the boss enough wall around the hole
Adding bulk creates new problems
Keep bosses away from edges and corners
Watch out for the knit line
Sizing the Pilot Hole
Driving the Screw Without Overloading the Part
Reusing the Same Hole
Reading a Failed Joint
How to Choose the Right Setup for Your Plastic Part
1. Is the plastic flexible or brittle?
2. How many times will this joint be opened?
3. Is there room for a proper boss?
4. What will the assembly line actually have in hand?
5. What conditions will the joint live in?
6. Has it been tested on real parts?
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