Dependence of geometrical parameters change of M6 thread on T torque

While operating various constructions and machines, the increase in loosening of threaded joints was observed. In the process of framing parts, when the torque is controlled, the bolts come loose after 200 hours of engine running. Thus, connections become inefficient, the stress decreases in one place and increases in another and this results in breakdowns. The paper investigates the dependence of M6x100 thread geometrical parameters of 8.8 grade bolts on the torque. The obtained data suggests that the torque influences thread geometrical parameters. When there is a friction in the M6x10 thread of 8.8 grade bolts, thread profile angle α increases from 0,1…2,1 % and thread pitch P increases from 0,26 to 34 µm. When there is a friction in the thread and bearing surface of a nut, thread profile angle increases from 0,1…1,7 % and thread pitch in-creases from 0,25 to 31 µm. A combined method should be used for bolt tightening when both torque and elongation of a bolt are controlledVytauto Didžiojo universitetasŽemės ūkio akademij