The dynamometric wrench is an essential tool that allows to perform controlled bolting on screws, nuts, pins and bolts, at the correct torque value: this means that it is able to put a bolt in traction with calibrated force that stays under a specific threshold, in order to hold two parts together without damaging the threaded part of the bolt.
It is an essential tool the you need to perform a correct and safe controlled bolting, to guarantee the impeccable operation of the system you are working on. This is why, for example, it is used in mechanical workshops, to work on cars and motorcycles tires and to allow the vehicle to travel in complete safety.
HOW TO CHOOSE A TORQUE WRENCH
In order to answer to this question, we just have to follow two fundamental steps:
- First, you should verify that the tool holds a DIN EN ISO 6789 certification, standards that guarantee the reliability and safety.
- Then, keeping in mind what you want to use it for, you should decide wether you should opt for a mechanical or a electronic torque wrench.
Generally, all models of this wrench have a ratchet head or a control panel that allows the coupling of the socket wrenches. On most models there is the option to adjust the torque through the main scale and the nonius, in order to always exert the correct torque on the screws. Lets now look at the two main types of torque wrenches.
It’s a pretty inexpensive and very sturdy model: the absence of electronic parts allows for less damage risk in case of accidental landfall. However, it’s not possible to save the data of every tightening which means you have to apply the torque each time: this makes it easier to risk over tightening.
The mechanical torque wrench is also known as click torque wrench: the name is due to the click that the wrench makes when it reaches the preset torque value, at this point it also softly vibrates due to the disengaging of the internal mechanisms. After the click, the rearming of the wrench happens automatically as soon as the force on the application spot stops.
Also known as digital torque wrench, this tool is more expensive but offers greater advantages. It is equipped with torque sensor, which always grants the correct tightening thanks to data displayed on its screen: you can save the gathered data and use them again for similar tightenings, with no errors. The more up-to-date versions can also be connected to a computer via USB, to save all useful data in the software database.
HOW TO USE A DYNAMOMETRIC WRENCH
First, you need to understand what the default unit of your wrench is. Usually they are produced in N · m unit (Newton meter) which is adopted by the International Metric System, or in Ft · Lbs unit (foot pound force) or in · Lbs (inch pound force) for instruments from the Anglo-Saxon Countries.
Then, you need to know the torque value needed to perform the tightening of the component: if you don’t know it, you can easily find unified charts, outlining the average values of reference according to the material of the component on which you are working. At this point, all is left to do is set the value needed to start the tightening job.
Once the job is done, it’s crucial to remember to reset the scale to the minimum, in order to avoid the decalibration of the spring located inside the spring. However, after a certain number of uses, you will still need to recalibrate: the ISO 6789 standard recommends recalibration every year or after 5000 tightening cycles.
When you purchase a torque wrench, remember to only choose products with appropriate certificate, and only choose the best brands: even if you buy it for personal use, to work on your bike for example, it’s crucial that you choose a reliable tools that will assure a correct tightening of screws and bolts.