BENSONS has started its activities in the year 2013, dealing with Trading & Manufacturing of Fasteners & Engineering Product with a vision to enterprise, which will cater to the requirement of the industries in the part of the state or country with Quality.
The proper amount of tightening (or pre-load) is important. If the fasteners are too tight they may break - either during the tightening itself or when the working load is added to the pre-load in applications such as gasketed joints. If too loose, the fastener will shake loose in vibration. Often overlooked, but equally important, is the tendency of fasteners subjected to cyclic loading to fail from fatigue if not sufficiently tightened.
In this method, the nut or bolt is turned a predetermined number of degrees after all play has been removed from the joint. How much to turn the nut or bolt cannot be calculated (because of the "rubberiness" of the joint) but must be developed by tests for each joint. It eliminates the friction factor; however, its accuracy is affected by the care of the workman in measuring the angle the nut or bolt is turned.
Preload indicating (PLI) washers utilize compression of an inner ring between two flat washers with an outer indicating washer for control. As the load increases, the inner ring, which is higher than the outer one, is squeezed down and enlarged in diameter until the outer washer binds against two flat washers. When the inner ring has been flattened to this point, the correct clamping force has been reached.
In this method, a bolt from the lot is loaded in a tensile machine with the same nut as used in the application. The distance from the nut face to the underside of the bolt head is measured, and a plot is made of bolt elongation in relation to induced load. In the application, the fastener is tightened and the bolt elongation is measured until the required preload as determined from the plot has been achieved.
