A screw differs from a self-tapping screw in many characteristics, for example, such as the strength of the material of manufacture and the shape of the product. But the main differences relate to the way of use and directions of application.
Technical differences between a screw and a self-tapping screw
A screw and a self-tapping screw are fasteners, which are a rod with a head and an external thread. In some sources, it is believed that a self-tapping screw is a type of screw. The functional characteristic of this product is the creation of an internal thread in the hole of the connected object.
The external thread on the surface of the screw occupies half or less of the entire length of the rod, with a smooth surface near the head and a threaded surface near the tip of the rod. The external thread of a self-tapping screw either covers the entire surface of the rod, or most of it. In addition, the thread height and pitch of a self-tapping screw is greater than that of a screw. The thread height of the screw from the end to the base of the rod increases to a greater extent than that of a self-tapping screw. The rods are also distinguished by their sharpness - the self-tapping rod is sharper sharpened. The self-tapping rod itself is thinner than that of the screw.
There is a triangular thread on the cylindrical surface of the screw and self-tapping screw - for a self-tapping screw, this thread covers the entire surface of the outer part of the head, and for a screw only a part. This difference determines the higher product durability of the screw from a technical point of view. On the actual side, self-tapping screws are made from more durable materials, which makes them much stronger than screws. Self-tapping screws are usually made from hard steel grades such as hardened steel. The use of alloys with increased strength is due to a special technology for the manufacture of self-tapping screws, including heat treatment at high temperatures.
In the very technique of using these fasteners, there is an important difference: before using the screw, the hole for the fastener is pre-drilled with a drill to create a guide channel, the self-tapping screw is used immediately due to the sharpness of its rod and the material of manufacture. When drilling a hole for a screw, it is recommended to clean the hole from construction dust to reduce stress when tightening the rod. The self-tapping of the self-tapping screw into the material without preliminary drilling is explained by the sharpness of the rod and the increase in the thread height.
The screws are designed for working with soft materials - wood, plastic. Self-tapping screws are used for working with solid products - concrete, metal. Therefore, the material for the manufacture of self-tapping screws is more durable and has a phosphated coating to protect against corrosion.