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Must-read for sheet metal processing: How to select self-tapping screws? Practical skills to avoid cracking and stripping

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Must-read for sheet metal processing: How to select self-tapping screws? Practical skills to avoid cracking and stripping

2025-05-19

In sheet metal processing, self-tapping screws are one of the most commonly used fasteners, but improper selection may cause cracking, stripping, loosening and other problems, affecting product strength and assembly efficiency. How to choose suitable self-tapping screws based on material thickness, load requirements, and environmental factors? This article will share key selection factors and anti-failure tips to help you optimize sheet metal fastening solutions.

1.Four Key Factors in Self-Drilling Screw Selection

Sheet metal material and hardness

Different metals (such as cold-rolled steel plates, stainless steel, and aluminum plates) have large differences in hardness, which directly affects the penetration ability of self-tapping screws:

Soft materials (aluminum, copper): suitable for fine-thread screws to reduce the risk of material deformation.

Hard materials (stainless steel, thick steel plates): coarse threads or drill tails (TEK screws) are required to ensure smooth penetration.

Matching plate thickness with screw length

Screw length = plate thickness + 2~3 times the pitch (to ensure complete engagement and avoid stripping).

Too short: insufficient thread engagement, easy to loosen; too long: may penetrate or interfere with the internal structure.

Head type and assembly method

Pan head/countersunk head: used in places with high requirements for surface flatness.

Hexagonal head/flange head: provides higher torque and good anti-loosening effect.

Self-drilling tail (TEK): suitable for thicker plates, no pre-drilling, and improved efficiency.

Surface treatment and environmental adaptation

Galvanized: general anti-rust, suitable for indoor environments.

Dacromet/stainless steel: corrosion-resistant, suitable for outdoor or humid environments.

2.Three practical skills to avoid cracking and stripping

Pre-drilling optimization (for high hardness materials)

On stainless steel or thick steel plates, you can first drill a pilot hole (hole diameter ≈ 70% of the screw core diameter) to reduce penetration resistance and reduce the risk of cracking.

Control tightening torque

Excessive torque: causes material deformation or thread slippage.

Insufficient torque: loose engagement and easy to loosen.

It is recommended to use a torque screwdriver, referring to the standard value provided by the manufacturer.

Select anti-loosening design

With nylon washers: increase friction and prevent vibration loosening.

Double thread design: improve meshing strength, suitable for dynamic load scenarios.

3.Frequently Asked Questions (Q&A)

Q: Self-tapping screws are easy to slip on thin plates. How to solve it?

A: Use fine-thread screws or self-tapping screws with cutting edges to improve thread bite force.

Q: Ordinary self-tapping screws are easy to break on stainless steel plates. What should I do?

A: Choose 304 or 316 stainless steel screws and pre-drill small holes to reduce the penetration stress.

Q: Frequent disassembly and assembly lead to thread failure. What are the alternatives?

A: Use rivet nuts (Rivnut) or threaded sleeves to enhance durability.

Summary

The selection of self-tapping screws needs to comprehensively consider the material, plate thickness, load and environment, reasonably match the head type and surface treatment, and control the tightening process to avoid problems such as cracking and stripping. For special working conditions (such as high vibration and corrosive environment), anti-loosening or corrosion-resistant models can be selected, or combined with pre-drilling and thread reinforcement technology to optimize the solution.

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