There are many more thread-forms not listed here. This is a discussion of some of them, or at least the ones you’re most likely to run into. (Other related forms such as Taptites, PlastiHold, and Hi-Lows are listed elsewhere.) These products are available in steel and stainless steel.

• TYPE F (MACHINE SCREW) This thread-cutting screw may be used for making fastenings to castings (ferrous and non-ferrous metals) forgings from brass or bronze, heavy gauge sheet metals, structural steel, plastics, and resin impregnated plywood. Holes may be drilled, punched, or molded, depending on the material. Type F screws provide tight, vibrationless fit with high resistance to torque, shear, and tension.
• TYPE 1 (MACHINE SCREW) Type 1 thread-cutting screws are made for use in metals. Use them as general-purpose fasteners for almost any fastening purpose in harder metals such as steel, special alloy steels, and cast iron. They perform their thread cutting function in metals of any thickness and may be used over and over. Because these screws possess almost twice the strength of ordinary machine screws, much smaller screws can be used. When driven into untapped holes (drilled or punched) they stay snug in their self-cut, perfectly mated threads.
• TYPE 23 (MACHINE SCREWS) These specially designed self-threading screws are for use in zinc, aluminum, and other soft metal die castings. Employing a wider thread-cutting slot, they allow ample clearance for chips. The off-center slot presents an acute angle, with sharp cutting edges for best cutting performance. Type 23 screws are often used in plastics where a standard machine screw thread is desired. They can also be used in harder metals where the advantages of a wide cutting slot are important.
  
• TYPE 25 (SHEET METAL SCREW) This hardened steel screw for plastics is characterized by a wider thread-cutting slot, acute cutting edge, and wide spaced threads. Chips won’t clog; less driving torque is required; Also, free-cutting action greatly reduces internal stress of plastics as the screw is driven. This reduces the possibility of fracturing brittle plastic substances.
• TYPE 17 (WOOD, DRYWALL, and PARTICLE BOARD SCREWS) This is typically used as a reamer for wood applications. However, it’s often seen on roofing screws (sheet metal-type) as well.

Talk to Hardware Everywhere’s knowledgeable customer service team for help choosing the fasteners that match your application. Call us at 1-800-432-8979 or contact us online.