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Hardware screw nut (knowledge of automobile special screws)
- 2019-01-16-

                    Many car repairmen have dubbed themselves "screwed screws." Why is that?


BecauseAuto Special ScrewsIs the most used parts in the car, the bolts have different shapes, the numbers on the bolts are different. What do these mean? Today, brothers and sisters come to everyone to talk about the knowledge of car bolts!

Thread Categories

The winding direction of the thread is divided into left and right swivel threads, and most of the thread direction is right-handed thread, and a few special parts use the left spin thread.


The number of threads can be divided into single-threaded, dual-threaded, and three-wire processes, where single lines are used for coupling and other threads are used for transmission.

The shape of the thread is divided into triangular threads, rectangular threads, trapezoidal threads and jagged threads. Among them, triangular threads have good self-locking, high thread strength, usually used for connections, and are the most widely used threads.

According to the stadium, it is divided into two categories: coarse teeth and fine teeth. A coarse thread is a basic thread. The thread of the thin line is high, but the strength of the thread is lower than the strength of the coarse thread. It is commonly used in thin-walled fittings, shaft components and precision. Adjustment mechanism. When the screw diameter is greater than 70 mm, only fine threads can be used. There are several common threaded connectors for bolts, nuts and washers

Threaded self-locking and anti-loosening devices

Theoretically, all car-specific screws are self-locking and do not loosen under static loads. However, under alternating loads, alternating shocks, and vibration loads,

The coupling may lose its self-locking effect and loosen, so in order for the connection to be reliable, a locking device must be used. Typically, these two types are anti-loosening by friction and mechanical means.

The threaded connection is fixed on the top nut. Spring washer, self-locking nut, high strength self-locking bolt, fastening glue on thread, opening pin, stop washer, series wire, slotted nut, stop washer, etc.

Fastening method and fastening principle of automobile special screws

1, before connecting bolts, to ensure that bolts and nuts have pitch, tooth type, rotation direction and other parameters;

2, tighten before thoroughly clean the bolt hole sludge, carbon accumulation, coolant or oil and other debris and liquids, check whether the thread is intact, bolts are elongated, 3, tighten the bolts, please follow the torque specified in the instruction manual tightening. If not specified, the fastening torque is determined according to the bolt diameter;

4. When removing the cylinder head bolt, it must be carried out after the engine has been completely cooled. When disassembling, follow the principle of "loosening from both sides smoothly to the middle diagonal direction" to prevent the warping deformation of the cylinder head;

5. When the same part is fixed with multiple bolts, it shall be tightened gradually in a certain order according to the shape of the connecting parts and the distribution of the bolts (generally tightening 2~3 times). If there is a positioning pin, it should be close to the positioning pin. Bolt start;

6, tighten the square or round nut, they must be symmetrical;

7, tighten the rectangular nut, from the middle began to gradually and symmetrically spread to both sides.

When repairing a car, various screws need to be removed. If the operation is not standard, it is easy to cause deformation or even damage to the parts. Each screw on the car is accurately calculated.

Its material, strength, fastening torque, deformation and other strict control. In the car factory,Auto Special ScrewsDisassembly is very standard and there is no need to go to the repair shop.

Many maintenance personnel do not use torque wrenches, simply tighten the bolts with their hands, or replace the high-strength bolts with ordinary bolts. So some people say that the car is not bad, but fixed.