1. Pre-tightening of the fastener threaded connection 1. Threaded connection: Loose connection-it is not tightened during assembly and is only subjected to force when it is subjected to external load. Tight connection-it needs to be tightened when assembling, that is, it has been pre-stressed during load-bearing, pre-tightening force F'. 2

. The purpose of preloading is to maintain normal operation. For example, the cylinder bolt connection has tightness requirements, air leakage prevention, a large contact area, work by friction, and increased rigidity. Increase rigidity: increase connection rigidity, tightness and improve anti-loosening ability. Pre-tightening force F': Pre-axial force (tension). Pre-tightening: If the tightening force F'is too large, the static load of the screw will increase and its strength will be reduced.

Too loose: the tightening force F'is too small and the work is unreliable. 3.For example: Tightening torque of wrench: T=FtL, nut when tightening: T=T1+T2, T--tightening torque; T1--thread friction resistance torque; T2--friction between the annular surface of the nut end and the connected part Moment. Because the bolts with too small diameter are easy to be broken when they are tightened, they should not be smaller than M10~M14 for important connections.

Control of pre-tightening tapping screw suppliers measuring torque wrench-measure the pre-tightening torque, as shown in the figure below; fixed torque wrench-when reaching a fixed tightening torque T, the spring will automatically slip under pressure, as shown in the figure below; measuring pre-tightening The extension of the front and rear bolts-higher accuracy. 2. Anti-loosening of the threaded connection of fasteners 1. In actual work, the external load has vibration, change, high-temperature creep of the material, etc., which will cause the friction to be reduced.

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