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Why do Fasteners Have "Reverse Deduction"?

Jun. 29, 2020

As a Railway Fastening System Manufacturer, share with you.

In daily life, many small friends will find that when they loosen the screws, the more they tighten, the more they try to find that some screws are turned counterclockwise. Why is this happening? The reason is that the screws have positive and negative threads The points of silk can also be called positive buckle and reverse buckle.

Hex Bolt

Hex Bolt

Left and right thread comparison

Positive buckle is common, tighten clockwise and loosen counterclockwise, while the application of reverse buckle is less, and the tightening method is opposite to positive buckle. Reverse screws are generally made according to needs and requirements, usually to prevent reverse. According to the direction of rotation, it is less likely to cause torque attenuation and more reliable than the right-hand screw.

Rectangular countersunk screw

The scientific name of the reverse buckle is "left-handed screw". As the name implies, it is the reverse of the normal fastener screw, also called "reverse wire". The normal fastener screw is tightened clockwise, and the reverse buckle is to be tightened. It is counterclockwise, and when it is loosened, it is clockwise. Then why are there "reverse" fasteners? What mechanical equipment are generally used for "reverse" fasteners? Let me talk about "reverse" Buckle" fasteners.

Reverse fasteners are usually used in rotating mechanical equipment, such as fan blades, impellers in motors, vertical mills, bicycle pedals, air conditioner fan impellers, etc. There are also "left-hand screws" rarely used for safety, such as flammable gas tank pressure relief valves.

Bicycle left pedal

Taking the vertical mill as an example, when the mill is started, the spindle rotates clockwise, and at the same time drives the grinding wheel and lock nut to rotate.The grinding wheel and lock nut will give the spindle a counterclockwise rotation force due to inertia.The grinding wheel has a larger diameter Therefore, the inertial force is also large. The inertial force of the grinding wheel is transmitted to the nut through friction. The nut will become tighter under the dual action of its own inertial force and the inertial force of the grinding wheel. If the left spindle is a positive buckle, the grinding wheel will loosen itself due to inertial force.

Vertical mill

Dangerous tanks such as gas tanks are also counter-buckles, in order to prevent unintentional persons from opening and causing danger. We must also develop a habit. When the screw cannot be opened according to the habit, and even tightened, the screw switch should not be opened casually, and the operation should be carried out after understanding the situation.

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