Which are self-tapping fasteners, or self-drilling screws, have a very small carving at the end of their tip, called a drill bit. These screws are very popular since they eliminate the need to pre-drill, which cuts back on the number of steps necessary to complete projects. These screws are meant for metal to metal applications only, with the exception of the reamer Tek screw which is designed exclusively for a wood to metal application.
Standard self-drilling screws were never designed to go from metal to wood. This is because the diameter of the hole that the drill bit creates will be close to the same diameter as the outside threads of the threaded portion of the fastener. If that’s the case, this will not allow the threads to tap into the wood and be secure. The exception to this are some self-drilling screws that are manufactured for roofing applications. The drill bit on those screws is very tiny, a #1 drill bit, and the diameter of the hole that the drill bit makes is substantially smaller than the diameter of the outside threads of the rest of the screw. This allows the threads to really bite into the material and allow the screws to self-tap into the metal or wood for a secure hold.
Contractors use Tek screws for screwing metal to metal and sometimes wood to metal. Depending on the thickness of the material you are drilling into, you have several drill points available, the longest being a Tek® 5, sometimes referred to as a ‘beam buster’. These particular screws allow the user to fasten two pieces of material together without pre-drilling.
These screws come in varying sizes. In the case of hex head tek screws, check out our video to help you understand how to determine the size of screws based simply on the size of the hex head plus other additional information. Self-drilling screws are available in a variety of shank diameters and lengths as well as head styles. Depending upon the type of work you are using them will dictate which type you need to complete your project.
Two of the most common types of head styles on tek screws that you will find on the market are the hex washer head and modified truss. Flathead screws are used when you need a flush surface. The hex drive is the preferred drive of most contractors doing heavy-duty metal installations. Other than that, all other styles of heads on self-drilling screws generally have a Phillips drive although square drive is becoming more and more desired. Reamer tek screws, self-drilling screws with wings, are the ultimate wood to metal screws.
We are often asked for stainless steel self-drilling screws. They are available but the tips are not really the best for drilling into stainless steel. For this application, we suggest bi-metal tek screws, where the body of the screw is stainless but the tip is made of carbon steel which allows the screw to drill into the stainless
The values listed above are averages achieved under laboratory conditions and imply no warranty. Appropriate safety factors should be applied to these values for design purposes.
A minimum of 3 factors of safety should be used. Allow at least three full threads to extend beyond material.
The distance from the center of a screw to the end or edge of a metal member shall not be less than three times the screw diameter.
Steel members shall conform to section 2230, A3 of the code. 25ga, 20ga, 18ga-Astm A 653 Grade 33 S.Q. with a minimum of 33,000 psi yield strength. 16ga, 14ga, 12ga-Astm A 653 Grade 50 S.Q. with a minimum of 50,000 psi yield strength.