Mechanism and Features of Self-tapping Screws
- Self-tapping screws have various tip and thread patterns.
- Common features include a screw thread covering the entire length of the screw and a hardened thread for the intended substrate.
- For hard substrates like metal or hard plastics, a gap is cut in the thread to create a flute and cutting edge, allowing the screw to tap its own hole.
- For softer substrates like wood or soft plastics, a tapered tip is used to displace the surrounding material and form a hole.
- Some self-tapping screws have a blunt tip (type B) for use with a pilot hole, making handling and packaging easier.
Thread-forming vs. Thread-cutting Self-tapping Screws
- Thread-forming self-tapping screws displace material without removing it.
- Thread-cutting self-tapping screws have sharp cutting surfaces that remove the material as they are inserted.
- Thread-forming screws may have non-circular plan views like pentalobular or Taptite screws.
- Thread-cutting screws may have flutes machined into their threads, providing cutting edges.
Self-drilling Screws
- Some self-tapping screws, like the Tek screw brand, are also self-drilling.
- Self-drilling screws combine hole drilling, threading, and fastener installation into one motion.
- They are efficient for hard-substrate applications, from assembly lines to roofing.
- Some types of self-drilling screws incorporate a sealing washer for fastening roofing sheets to purlins.
Sheet Metal Screws
- Sheet metal screws can form a thread in thin sheet metal.
- Pan-head self-tapping screws are common in metal cases for electrical equipment.
- Flatter-headed truss or flat countersunk headed self-tapping screws are found in aviation applications.
Winged Self-tapper
- Winged self-drilling screws have thin wings wider than the thread formed just behind the self-drilling head.
- These screws cut a clearance hole in soft materials but are destroyed by more robust materials.
- They allow for a single operation to clamp material to metal, including clearance drilling, tap drilling, thread tapping, and fixing.
This article needs additional citations for verification. (April 2017) |
A self-tapping screw is a screw that can tap its own hole as it is driven into the material. More narrowly, self-tapping is used only to describe a specific type of thread-cutting screw intended to produce a thread in relatively soft material or sheet materials, excluding wood screws. Other specific types of self-tapping screw include self-drilling screws and thread rolling screws.
self-tapping screw (plural self-tapping screws)
