The torque wrench aids you knowing the exact torque applied to the fasteners. So that you can come to a conclusion that it is perfectly torqued. You may over tight or under tight a fastener when you use the normal wrench. So torque wrench is a common tool for a mechanic to carry in the tool box. When it comes to automobile, most of the components fastened are listed in the manual with designed torque range. Unfortunately, the range falls in a very short deviations. So the torque applied falls short, the fastener gets unscrewed and fall off during the travel. This stops on the roadways to call for help and force you learn how to use torque wrench. Excess torque compress the bolted parts and subject that to bending and crack. To avoid these, you are forced to have a torque wrench for your needs. Automobile manufacturing companies specify the torque value for every critical fasteners in the unit of foot pounds in the owner’s manual.
What is torque?
Torque is nothing but the twisting force around the fastener. Suppose you use one foot long wrench and apply a force of 5 pounds, now you applied a twisting force or torque 50 ft- lb. If you use 2 foot long wrench and apply 5 pounds, the applied torque is 100 ft-lb. so the applied torque is about the length of the wrench and applied muscle force.
Suppose you are using the beam type torque wrench to tighten the fasteners, the centre beam starts to bend when you apply force. The pointe attached to beam tells you the torque you are approaching and stop over tightening when you reach desired torque point. The very important thing in using the beam type torque wrench is that you have to keep your eye above the pointer so vertical. If you incline your eye contact, you may apply over torque. So reading the measurement may be subjected to manual error. Careful measurement ensures the safety level. The big advantage is the easy calibrations. Simply you adjust the pointer to zero then it is calibrated and ready to use. Go here: http://www.torquewrenchcenter.com for more information.
The click type torque wrenches are easy to read the measurement. You get audible click sound when you reached the correct torque level. Every time it has to be brought to zero, to begin the measurement. Calibration has to be done for critical parts and it is mandatory to learn how to use torque wrench for measurement. When you use the torque wrench for tightening the fasteners in engine head, oil tank and other oily surface, the bolt and nut threaded surface is wet. So they offer more slip. You have to reduce the torque level by 15 to 20 percent. If you are giving attention to this advice, the fastener gets over tight. It is dangerous too. Some lubricating oil offers frictional reduction up to 50 percent. So torque setting also to be reduced for the level to avoid failure of fasteners. If there are some dust over the thread force, this increases the friction. So torque has to be adjusted or clean the surface with brush. The manual clearly dictates the torque to be applied for wet and dry surfaces. So enough attention is required to read the manuals.