A self-tapping screw drive is a specialized type of tape-ring screw which is able to tap into its hole when it’s driven into the work material. More precisely, self-tuning is used to describe a special type of flat-ended thread-cutting tape screw designed to make a thread into relatively soft materials, excluding wood and metal screws. These are commonly called T-nuts or simply nuts. There are several types of such threads, including tubular threads, tapered threads, slanted threads and a center-set thread.
There is also another kind of self drilling screw, which is basically a variation of the tap-and-ratchet mechanism mentioned above. In this case, the tap is positioned into the hole, which may be either a small cut in the work material or a slit created by drilling. The working with such a screwdriver is basically identical to that with a tap-and-ratchet mechanism – the difference lies in the way the screwdriver is forced into its hole by a counterweighted force. When the thread is driven deep into the work piece using such a screwdriver, a pilot hole is created on the opposite side of the threads to allow some amount of thread to escape before the screws get fed through. Additional info found at self tapping screw.
This type of screw is commonly used for threading plastic, thin steel, sheet metal screws and other thin materials. They have a similar action as tap and ratchet screws, but because the driving force comes from a counterweighted force acting on the threads, the result is a faster tightening of the thread than with other types of screws. This makes them suitable for use in applications where the threading operation is not very sensitive, such as in plastic strapping or T-nuts. They are often used as joint-end screws and as a substitute for a tap.
There are two types of self-fitting screws that are widely used for threading soft materials. The first is the threaded kind, which is the most common – the threads are drilled directly into the hole. The second is the self taper screw, which has a tapered, slightly tapered hole. The inner diameter of the tapered hole depends on the type of material being used and the load required. They are frequently used in conjunction with other types of screws to provide a variety of fastening options.
The screw threads may pass through a small brass hole, which is an essential part of the fastener. To align the screw holes and keep them parallel to each other, there are motorized screw collars. One such collar has a small hand crank attached to it, which rotates the screw at the same speed as the arm of the screwdriver threading tool. A faster rotation can mean better tightening, although this is not always necessary.
In order to install self drilling screws in soft materials without over-tightening or damaging the hole, you need to drill at a slower rate. The soft spot to be drilled needs to be bigger than the diameter of the screw you want to use for alignment. Drill a small pilot hole before you screw the collars onto the soft surface, so you can start tightening the screws before putting the screws in place. You can tighten them as you go along, until the screw holes in the collars have been adequately reinforced.
Successful Video Blog 