The Advantages of Threaded Fasteners

Thread can be divided into cylindrical thread and taper thread on the basis of its main body shape; also is grouped into the external thread and internal thread by its location on the mother cylinder; further is classified into triangle thread, rectangle thread, trapezoidal thread, serrated thread and other special thread forms depending on its cross-sectional shape (tooth type).

With a threaded fastener, the clamping force holding the two pieces of material together is produced by a torque being applied to the fastener to stretch it and this is maintained during the service life of the fastener. The fastener is in tension and the two pieces of material in compression. The common types as we know are bolts mated with nuts, rivets with insert rivet nuts and screws with threads in the material.

Knowing the proof strength of fasteners will contribute to the correct selection of fasteners used in materials. The low- or medium-carbon steel bolts will typically have a minimum proof strength of about 225 to 400 Pa, the proof strength being the maximum stress the bolt can withstand without acquiring a permanent set. For quenched and tempered mediumcarbon bolts the minimum proof stress is 600 to 650 MPa and quenched and tempered alloy steel about 970 MPa.

Threaded fasteners are particularly useful for joining components that are likely to need to be dismounted during the life of the product.