A wrench is a manual tool that uses the principle of leverage to turn bolts, screws, nuts, and other threaded fasteners that hold the opening or socket of a bolt or nut.
Its working principle is to have a clamp on one or both ends of the handle to apply external force. By applying external force to the handle, the bolt or nut can be turned to hold the opening or sleeve hole of the bolt or nut.
When using a wrench, external force should be applied to the handle in the direction of thread rotation to turn the bolt or nut. Wrenches are usually made of carbon structural steel or alloy structural steel.
There are basically two types of wrenches: dead wrenches and live wrenches
- Dumb wrench (Dumb wrench)
One or both ends have fixed sized openings for twisting nuts or bolts of a certain size. Dumb wrench, also known as open-end wrench, has two types: single head and double head. - Plum wrench
Both ends have working ends with hexagonal or twelve corner holes, suitable for situations where the working space is narrow and ordinary wrenches cannot be used.
Compared with open-end wrenches, the plum blossom wrench has higher strength and is less likely to slip off during use, but it is inconvenient to put on and take off. Its specifications are expressed in closed mouth size S (mm), usually as a complete set of equipment, with 8 pieces per set, 10 pieces per set, etc. It is usually forged with 45 steel or 40Cr and subjected to heat treatment. - Dual purpose wrench
One end is the same as a single headed wrench, the other end is the same as a ring wrench, and both ends are twisted with bolts or nuts of the same specifications. - Hexagonal wrench
It is used for disassembling and assembling hexagonal bolts (plugs), with specifications represented by the size S of the hexagonal opposite side, and there are thirteen types ranging from 3 to 27mm. A complete set of hexagonal wrenches is used in automotive maintenance operations, which can be used for disassembling and assembling M4~M30 hexagonal bolts. - Socket wrench
It is composed of multiple sleeves with hexagonal or twelve corner holes and equipped with various accessories such as handles and connecting rods, especially suitable for twisting bolts or nuts with very narrow or deeply recessed positions.
A socket wrench is mainly composed of a socket head, a handle, a ratchet handle, a quick rocker handle, a joint, and a connecting rod. Various handles are suitable for various occasions, and the commonly used socket wrench specifications are 10-32mm, based on the principle of easy operation or improved efficiency. Many specialized socket wrenches are also used in automobile maintenance, such as spark plug sockets, wheel hub sockets, tire nut sockets, etc. - Torque wrench
It is a specialized tool that can read the magnitude of the applied torque, and its specifications are divided based on the maximum measurable torque. There are two commonly used types: 294N · m and 490N · m; In addition to controlling the tightening torque of threaded parts, torque wrenches can also be used to measure the starting torque of rotating parts to check fit and assembly conditions. - Activity wrench
Its opening size can be adjusted freely within a certain range, and it is used in the same situation as an open-end wrench, but the adjustable wrench is not very flexible to operate. Its specifications are expressed in terms of maximum opening width (mm), commonly including 150mm, 300mm, etc.
Summary: Correct selection of wrench tools
(1) The opening size of the selected wrench must match the size of the bolt or nut. If the opening of the wrench is too large, it is easy to slip and damage the hexagon of the screw. In the maintenance of imported cars, attention should be paid to the selection of wrench metric and imperial systems. The selection principles for various types of wrenches: generally, socket wrenches are preferred, followed by ring wrenches, then open-end wrenches, and finally adjustable wrenches.
(2) To prevent damage and slippage of the wrench, the tension should be applied to the thicker side of the opening. This is especially important for adjustable wrenches that are subjected to high stress to prevent the opening from forming an “eight” shape, which can damage the nut and wrench.
(3) Ordinary wrenches are designed based on the strength of human hands. When encountering tight threaded parts, the wrench cannot be hit with a hammer; Except for socket wrenches, other wrenches cannot be equipped with force rods to prevent damage to the wrench or threaded connections.
