December 16, 2023
Locking - fasteners include: bolts, studs, screws, nuts, washers, pins. Locking or seizure often occurs on fasteners made of stainless steel, aluminum alloy and titanium alloy. These metal alloys themselves have anti-corrosion properties. When the surface is damaged, a thin oxide layer will be produced on the metal surface to prevent Further corrosion. When stainless steel fasteners are locked, the pressure and heat generated between the threads will destroy the oxide layer, causing blockage or shearing between the metal threads, resulting in adhesion. When this phenomenon continues to occur, the stainless steel fastener will be completely locked and cannot be removed or locked again. Usually this series of blocking, shearing, sticking and locking actions occurs in just a few seconds. Therefore, only by correctly understanding and using this type of fastener can we prevent this phenomenon.
1. Choose the product correctly
a. Before use, confirm whether the mechanical properties of the product can meet the usage requirements, such as the tensile strength of the screws and the guaranteed load of the nuts. The length of the screw should be selected appropriately so that 1-2 pitches of the nut are exposed after tightening.
b. Before use, check whether the threads are rough and whether there are iron filings or dirt between the threads. These things often cause locking.
c. The fasteners can be lubricated before use. It is recommended to use butter, molybdenum disulfide, mica, graphite or talcum powder for lubrication. Generally, wax impregnation is used for lubrication and anti-locking.
2. Pay attention to the usage method when using
a. The screw-in speed and force should be appropriate, not too fast or too large. Use a torque wrench or socket wrench as much as possible, and avoid using adjustable wrenches or electric wrenches. Excessive speed will cause the temperature to rise rapidly and cause locking.
b. In the direction of force application, the nut must be screwed in perpendicular to the axis of the screw.
c. Using washers can effectively prevent the problem of over-tightening.