The basic rule of thumb says that the more you are using a tool, the quicker it will wear or go out of calibration. Optimizing tool usage can reduce wear, but won’t make it last forever. Also, in the tools required for precision work and measurement, calibration is also a decisive factor that needs to be taken in consideration in maintenance applications. A good example that fits the latter category is the torque wrench.
What is a torque wrench?
Just like regular wrenches, a torque wrench is used to fasten and tighten a nut or a bolt. However, unlike its classic version, the torque wrench allows the user to precisely set the amount of torque used while tightening. This is particularly useful its precision assemblies such as engine gasket or lug nuts. A preset torque level allows for proper tension and uniform load on all the parts that are connected with the screw and nut system.
There is more than one type of torque wrenches; depending on their mechanisms. You may own a slipper type, which will stop tightening the nut or bolt once the present amount of torque is achieved or a beam torque wrench type, which elastically bends according to the amount of force used.
Deflecting beam and click type torque wrenches employ more advanced and efficient torque measuring or limiting mechanisms, but are also more expensive. Even more recent torque wrenches come with electronic displays that show precisely the amount of torque used, down to the last Nm.
Maintaining torque wrenches
On average, torque wrenches are built to work properly for up to 100,000 cycles, then requiring maintenance and recalibration. Fortunately, there aren’t too many mobile parts in a torque wrench, thus the maintenance process shouldn’t take too long or be too expensive.
First of all, the handle of a torque wrench should be inspected for cracks or other defects that may have been developed during usage. A thorough clean to remove chemicals and grip-reducing lubricants is highly recommended.
The ratchet should be treated with increased attention as it represents the biggest mobile component of the mechanism. Ensuring that old or dry grease is removed and new, temperature resistant one is added is a must. Also, the ratchet should move freely when rotated, while also ensuring that screws are tightened properly.
Calibrating torque wrenches
As mentioned in the first paragraphs, torque wrenches are usually made using a spindle and spring in order to measure the amount of torque applied to the nut or bolt. Leaving the wrench calibrated at a specific setting will eventually affect the linearity of measurements. Thus, it is highly important to reset the torque setting to its default value when the job is completed, then store the wrench into an adequate case, to be protected from chemicals and possible mechanical shocks.
Torque wrenches can be checked for accuracy by using a torque tester. Regular accuracy checks will ensure the amount of torque shown or limited by the wrench is close enough to the actual force applied by the user, and thus resulting in a properly tightened system.
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