What Are Bolts And Types Of Bolts

A bolt is a threaded fastener with a cylindrical rod. The cylindrical part with a thread at one end is called a stud, which is used to fit with the nut. The other end is the head, called the bolt head. Bolts are usually made of metal. They are also made of various non-metallic materials for special occasions such as electrical insulation or corrosion protection.

A bolt is used to join or fasten in a mechanical structure or building member. It is usually classified as a fastener when fixed in a mechanical part. Bolts are manufactured in the vast majority of cases in accordance with the relevant national or international standards, so in the business circulation, bolts will be classified as standard parts together with some other parts also produced according to the mandatory standards. Bolts, screws and nuts are commonly known or generally referred to as screws in many regions and non-technical contexts.

The difference between bolts and screws

The difference between bolts and screws lies in two aspects: one is the shape, the stud part of the bolt is strictly cylindrical, used to install the nut, but the stud part of the screw is sometimes conical or even with the top; On the other hand is the use, screw into the object is the target material rather than the nut. In many use cases, the bolt is also a separate work, is directly screwed into the pre-drilled hole, do not need the nut to cooperate with it, at this time the bolt is classified as a screw from the function.

The types of bolts

There are many types of bolts, but in most cases, they are distinguished by their studs and bolt heads.

• The thread of the column can be divided into coarse tooth thread, fine tooth thread and inch thread, so it is called fine tooth bolt and inch bolt;
• The shape and use of the bolt head are different and divided into hexagonal head bolts, square head bolts, semi-round head bolts, countersunk head bolts, hole bolts, T-shaped head bolts, hook head (anchor) bolts and so on.
• According to the attached expansion parts, there are expansion bolts.
• According to the material used in production and manufacturing accuracy, there are high-strength bolts, high-precision bolts and loose bolts and so on.
• Bolts can be classified into more than 10 grades according to performance levels, such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc. The bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and have been heating treated (quenching, tempering), which are generally called high-strength bolts, and the rest are commonly called ordinary bolts. The bolt performance grade label consists of two parts, respectively representing the nominal tensile strength value and flexure ratio of the bolt material.

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