How to choose fasteners

Fasteners include: bolts, studs, screws, nuts, washers, and pins. Locking or seizure often occurs on fasteners made of stainless steel, aluminum alloy and titanium alloy. These metal alloys have anti-corrosion properties. When the surface is damaged, a thin oxide layer is formed on the metal surface to prevent Further corrosion. When stainless steel fasteners are locked, the pressure and heat generated between the teeth will destroy this oxide layer, causing blockage or shearing between the metal threads, and then adhesion. When this phenomenon continues to occur, the stainless steel fasteners will be completely locked and can no longer be removed or continued to be locked. Usually this series of blocking, shearing, adhering, and locking actions occur in just a few seconds, so a correct understanding of the use of such fasteners can prevent this phenomenon.

1. Choose the right product

a. Before use, confirm whether the mechanical properties of the product can meet the use requirements, such as the tensile strength of the screw and the guaranteed load of the nut. The length of the screw should be selected appropriately, which shall be subject to 1-2 pitch of the exposed nut 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 talc for lubrication, and generally use wax dipping for lubrication and anti-locking.

2. Pay attention to the method of use when using

a. The speed and force of screwing in should be appropriate, not too fast or too big. Use torque wrench or socket wrench as much as possible, and avoid using adjustable wrench or electric wrench. Too fast will cause the temperature to rise rapidly and cause lockup.

b. In the direction of force, the nut must be screwed in perpendicular to the axis of the screw.

c. The use of washers can effectively prevent the problem of over-locking.