HEX WASHER HEAD SELF-DRILLING SCREWS
Copyright 2010: All Point Fasteners | Tek Screws. All Rights Reserved.
Self drilling screws, sometimes called tek screws, are self tapping in the same way as a sheet metal screw, but it has a drill-shaped point to cut through the substrate to eliminate the need for drilling a pilot hole. Tek screws are designed for use in soft steel or other metals. The points are numbered from 1 through 5, The larger the number, the thicker metal it can go through without a pilot hole. For example, a # 5 tek point can drill a 0.5 in (12.7 mm) of steel.
Contractors sometimes question the quality of their tek screws when the screws break, when the actual reason for breakage is the application for which they are being used. The following is a very simplified reason for heads of tek screws sometimes popping or screws twisting and breaking when drilled into steel too thick for the tek screw used.
Example: 12-24x 7/8 # 4 tek point HWH SDS
12 - (size of shank. Think dress size. Bigger the number thicker the shank)
24 – Number of Threads per Inch also known as TPI
7/8 – measurement from underneath the head to the tip of the screw.
With a standard tek screw, the front of the screw will be drilling in slower while the drill bit is drilling the pilot hole than when the threads of the tek screw catch the material being drilled. Once the threads catch, the screw will turn as fast as the TPI. In other words, if the screw is 16tpi, the screw will go in a 16th of an inch each time it turns. The problem becomes, if it is a thick piece of metal, the threads will catch before the drill bit is done drilling through the metal. The result is that the front of the screw will be moving slower than the back of the screw and the screw will break. However, by having the drill bit of the screw longer up the shank of the screw and changing the threads per inch to a finer thread (24 threads per inch), the front and the back of the screw will move at the same time and the tek screws won’t break.
Tek Type Screw
#4 Tek Point
Hi-Hat Tek Type Screw
with
Serrations
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