What is the Difference Between a Self-Drilling Screw and a Self-Tapping Screw?
One of the most important commercial fasteners in use today is the Self-Tapping Screw. Among the earliest “engineered” fasteners, Self-Tapping Screws were made from hardened steel and its use was instrumental to the Industrial Revolution. Still in use today, there are now many types and styles of Self-Tapping Screws made to perform specific fastening jobs.
Unlike Military or Aerospace Fasteners, terminology used in the Commercial Fastener Trade is often imprecise and can sometimes cause confusion; one example is the distinction between Self-Tapping and Self-Drilling Screws.
A Self-Tapping Screw can be referred to as simply a Tapping Screw. However it is also often called a Sheet Metal Screw because they are primarily used in sheet metal.
Whichever name is used, these names are for screws that form mating threads (“tapping” the threads) in a pre-drilled hole in the substrate into which they are driven.
A Self-Drilling Screw is a Self-Tapping Screw with the added feature of a drill point. The drill point looks a lot like the point of a drill. It will drill a hole and form the mating threads in one operation.
Here is where the confusion comes; many times the person specifying a screw will interchange the term Self-Tapping Screw (or “Self-Tapper”) with Self-Drilling Screw. If a screw will drill its own hole it is a Self-Drilling Screw.
Other screws that might be considered to be in the Self-Tapping Screw category are:
Thread-Cutting Screws (TCS) - These are screws that can be used to cut threads in a pre-drilled hole. There are many types of TCS and each has a different thread-form to accomplish that goal.
Thread Rolling Screws (TRS) - These are screws that will roll or extrude threads in a pre-drilled hole in the substrate without removing any material creating a fit with zero clearance.
While the terms Self-Tapping and Self-Drilling are not interchangeable, these screws come in numerous configurations and are widely used in the commercial, industrial and construction markets.
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