Self-Tapping Screws for Plastic: How to Choose the Right One

What Are Self-Tapping Screws?

Self-tapping screws can form their own threads as they are driven into the parent material. With plastic, this requires a specially designed thread profile. Tapping screws used with steel, for example, could result in residual stresses in the plastic that might degrade the structural integrity of the assembly. You can avoid this with self-tapping screws specifically intended for plastic applications. They also give you more flexibility and allow quick assembly of components with fewer fasteners.

How to Choose the Right Self-Tapping Screws for Plastic

When looking into self-tapping screws, the first step is to decide what type is best suited for your specific application. In general, self-tapping screws for plastic are classified into two categories: thread-forming and thread-cutting.

To choose the right screw category, it’s important to understand the type of plastic you are fastening into: thermoplastic or thermoset.

Thread-Forming Screws for Plastic

Thread-forming screws generally function best in thermoplastic materials. They produce no waste because the plastic that is displaced to create the thread flows back into the root of the thread, resulting in a very secure fit.

For example, the ecosyn® plast is a great option for a thread-forming screw for plastic. These screws are designed to easily penetrate the material without causing stress. Other advantages of ecosyn® plast screws include:

• Low driving torque and high stripping torque
• High breaking torque and tensile strength
• Excellent security against vibration
• Low risk of cracking the base material
• No setting of the assembly due to excessive relaxation of the plastic material

Thread-Cutting Screws for Plastic

Thread-cutting screws are designed for thermoset materials. These screws remove material because they have cutting edges. Thread-cutting screws have a smaller flank angle to reduce installation torque while increasing surface area, which results in a higher pullout force.