The industries produce numerous items with the help of different machines, and each of the machines here needs maintenance regularly. There are a few tiny devices that help the operator to fix these machines during maintenance activities as well as in routine operations. The bolts are small devices that hold various parts of the machines, and here it will be shown the means to manage or control preload with respect to the threaded fastener. Below are given few of the ways to know precisely the changes that take place while tightening the bolts and fixing them accurately.
Angle Controlled Tightening
This method can also be called as (turn of the nut method) which came into utilization concerning manual assembly in the year 1940’s shortly after the Second World War because the tightening angle was put to use. In this technique are brought in use the power wrenches wherein fastening of the bolt is done in accordance to prearranged angle in advance to the elastic range by which there occurs a small alteration in the preload due to the tolerance happening to yield stress in portion. By this way comes about bolt tightening. This system of tightening has some limitations associated with it which can be attributed to the unavoidability of exact determination by experiments and fastener gets failed with application of few times
Yield Controlled Tightening
This method of bolt tightening was put forth by SPS organization and is well-known as Joint Control Method under its proprietary name. By using this process, exact preloads are obtained by causing a reduction in the influence of friction also its extent. It is said that this way of tightening came into existence by a workman whose experience and sense about bolt fastening owing to the wrench which made him to make out the yield point by means of rational exactness of the fastener. With the utilization of electronic equivalent, furnished with torque calculation for bolt tightening, pertaining to this means there is provided a control system which can be said to be sensitive when talking of torque gradient that pertains to the bolt which is to be fastened. Due to its use, there is detection caused to the variation of incline in relation to the gradient indicates the yield point has been obtained and all the tightening process comes to a halt. All this process comes into being by utilizing sensors to determine torque and angle as the bolt is being tightened. The control system determines the torque, and the angle of rotation, values which are permitted can be employed to sense fasteners as are not by their specifications.
In this method can be seen a small degree of spread concerning preload due to the friction. The fastener experiences the act of tension and torsion and also the yield point can be sensed by this technique. Here the torsional stress can be said to be relative to the thread friction in which due to lower direct stress is marked lower preload with a given yield.