The Ultimate Tapping Screw for Plastics

The marketplace is flooded by offerings of some format of high performance self-tapping screw that claims to work better than anything else for threading into plastic. Most seem to have more than just general buzz going for them; different flank angles, tailored pitches, graduated point diameters, etc. Sometimes it appears as though they're all overlapping versions of the same technology. The plastic industry continues to develop dynamic alloys and new applications; fasteners have maintained pace. By definition the materials we are concerned with are called thermoplastics, all of which exhibit varying levels of flexibility and memory; for example, ABS (acrylonitrile), PC (polycarbonate), and Nylons. These and many others have "cold flow" properties and are ideal for self-tapping screws of the thread forming or thread rolling styles. Given that, let's focus on a thread design that isn't novel, but material, equipment and tooling have evolved to permit pitch, diameter and thread form combinations that generate remarkable results when threading into most thermoplastic alloys. What we are defining is a 30 Degree thread form called Type FT. By comparison, a standard Type B thread profile is 60 Degrees Included. A Plastite Twin Lead profile is 48 Degrees Included. The comparison shown in Figure A demonstrates the obvious advantages of a 30 Degree thread form: