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Types of bolts and classification basis

Posted By yong ding     Nov 16    

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Mechanical parts, cylindrical threaded fasteners with nuts. A type of fastener consisting of a head and a screw (cylinder with external thread), which needs to be matched with a nut to fasten and connect two parts with through holes. This type of connection is called bolt connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection is a detachable connection.

In life, bolts, screws, screws, etc. are often mentioned. What is the difference between them? In fact, the standard argument is that there are no screws and nuts. Screws are commonly known, and those with external threads can be called "screws". The shape of the nut is usually hexagonal, and the inner hole is an internal thread, which is used to cooperate with the bolt and tighten the related parts. The nut is commonly called, the standard should be called "nut". The head of the bolt is generally hexagonal, and the shank has an external thread. The screw is small, the head has a flat head, a cross head, etc., and the rod has an external thread. The actual stud should be called "double-ended stud", both ends have external threads, and the middle is generally a polished rod. The long end of the thread is used to connect to the deep hole, and the short end is connected to the nut.

Standard fasteners are divided into twelve categories, and the selection is determined according to the use occasion and function of the fastener.

A bolt is used to connect two objects, usually through a light hole, and needs to be used in conjunction with a nut. A single bolt cannot connect. Tools generally use wrenches. The heads are mostly hexagonal heads, etc., generally larger. Screws usually don’t need nuts, and are directly matched with two objects (generally, the connection piece needs to be drilled and tapped). The tool is usually a screwdriver (screwdriver). Generally small.

The thread of the stud can be divided into coarse thread, fine thread and inch thread, so it is called fine bolt and inch bolt;

According to the shape and purpose of the bolt head, it is divided into hexagonal head bolts, square head bolts, half-round head bolts, countersunk head bolts, bolts with holes, T-head bolts, hook head (foundation) bolts and so on.

The bolts are derived from expansion bolts according to the attached expansion parts.

Bolts can be derived from high-strength bolts, high-precision bolts, anti-loosening bolts, etc. according to the materials used in production and manufacturing precision.

Bolts are divided into more than 10 grades according to their performance grades: 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, among which grade 8.8 and above bolts are made of low-carbon alloy steel or medium-carbon steel and are heat treated (quenched Tempering), commonly known as high-strength bolts, and the rest are commonly known as ordinary bolts. The bolt performance grade label consists of two numbers, which respectively indicate the nominal tensile strength value and the yield ratio of the bolt material.

Anchor bolts: specifically buried in the concrete foundation, used as the base for fixing various machines and equipment.

Expansion bolt: Generally, a special threaded connection in the wall to install machinery equipment or structural parts on the concrete foundation.

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