Self-Drilling Screws

Self-Drilling Screws operate on the same principles as drill bits and other cutting tools. This means that the way in which these screws are used affects their performance as much as how they are designed.

 

Two important factors to consider when selecting a self-drilling screw are, material thickness and types of materials to be joined.

Table of contents depicting screw suitability and optimal cutting parameters

 

 

Key Design Features to Consider when Selecting a Suitable Self-Drilling Fastener

 

  • Drill FluteA self drilling screw with the names of every of its part

    • The length of the drill flute determines the metal thickness that can be drilled. Drill flutes allow the drilled material to exit the hole. If the drill flute becomes completely embedded in the material, the drill chips will clog the flute and cause the cutting action to cease. If this occurs, the heat from the drill chips could cause the drill point to become over-heated and fail.

  • Point Length

    • The drill point is the unthreaded section from the drill point to the first thread. This length must be long enough to completely drill through the material before the threads engage. If the threads engage too early, they can cause the fastener to bend and break.

  • Screw Wings

    • It is necessary to use fasteners with wings when fastening wood, over ½” thick, to metal. The wings will ream a clearance hole and keep the threads from engaging too early. If the threads engage too early, this could cause a separation of the fastened material from the base material (jacking). Once the wings hit the metal material, they will break off, allowing the threads to engage.

 

Self-Tapping Screws

Self-tapping screws can tap its own hole as it is being driven into it. They can come with a sharp, piercing tip or a flat, blunt tip. Sharp-tipped self-tapping screws are designed for drilling their own hole in soft materials. The flat-tipped self-tapping screws will need a pilot hole drilled before being installed. Some self-tapping screws are also self-drilling screws. These screws have a drill-like flute tip that looks like the tip of a center drill, along with the tap-like flute in the leading threads. These screws are very efficient in hard substrate applications.


How the Self-Tapping Ability is Created

  • Hard Substrates – Metal or Hard Plastics

    • Often created by cutting a gap in the continuity of the thread on the screw, this generates a flute and cutting edge similar to those on a tap.


  • Soft Substrates – Wood or Soft Plastics

    • The self-tapping ability can come simply from a tip that tapers to a gimlet point (no flute is needed); the point forms the hole by displacement of the surrounding material rather than any chip-forming drilling/cutting/evacuating action.

How To Use Self-Tapping Screws

The first thing you’ll need to do when using self-tapping screws is to mark your screw position. You’ll also need to ensure you have enough room to get to the desired area with a screwdriver or a drill.

Next is to drill the pilot hole. It’s often recommended to drill a hole slightly smaller than the screw you will use. This allows the self-tapping screw to better do its job by forming the thread inside the hole. 

Start the screw with a turn or two by hand to keep the screw in place while you reach for your screwdriver or drill. Fasten the screw using firm, controlled movements, and make sure that the screw is straight and not at an angle. Learn More about Self Tapping Screws Here

 

View the Tanner Self-Drilling Product Selection Guide to Find the Best Screw for the Job.