How Does a Torque Wrench Work?
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Do you have to use a torque wrench for the first time to fasten a nut or bolt? A torque wrench is an amazing specialty tool that is used in auto repair and construction tasks. Once a torque wrench is calibrated, it can help you figure out torque or rotational force.
The rotational force or torque is required to know how much effort is needed to fasten a nut or bolt. By using a torque wrench, you will fasten a bolt with less effort and more accuracy than with standard wrenches. While you might consider not using a torque wrench, studies have shown that amateur mechanics tend to overtighten just about everything.
Overtightening can lead to reduce functionality of equipment and can lead to stripped threads and damaged bolts.
Torque Wrench
You can extend the lifespan of your equipment and prevent threads and bolts from stripping or breaking using a torque wrench. One thing you must know is that there are several types of torque wrenches on the market today. There is a “clicker” wrench that lets you know that you’ve reached the correct torque with an audible click.
How Do They Work?
A torque wrench is a tool that is calibrated and is used for a specified amount of pressure, or load, to a nut or bolt. The torque amount that needs to be applied is dependent on the amount of force that you are applying on the handle and the overall length of the torque wrench. This is because torque is the force multiplied by the length of the tool.
For instance, if you have a one-foot long torque wrench, and you apply 40 pounds of force on its handle, you are using 40 foot-pounds of torque to the fastener you’re tightening. If, however, your torque wrench is, let’s say, two feet long, you’d start applying the same 40 pounds of force, the bigger tool will raise the leveraging effect to multiply the torque, which leads to you applying 80 foot-pounds of torque.
As you can see from what we’ve said above, the torque wrench shows you how much load is being applied to a fastener using a calibrated spring mechanism or a deflection beam. A display or scale on the wrench will show you how much load you are applying. The scale can usually be calibrated to show Newton-meters, inch-pounds, or foot-pounds.
Types of Torque Wrenches
There are four basic styles of wrenches: digital electronic, dial gauge, click adjustable, and beam style. The beam style is the most inexpensive and is easy to use. They can typically be bought for $30 or less online and in many auto part stores.
Several professional technicians prefer to use an adjustable click torque wrench because they are more accurate and faster to use. The digital electronic and the dial gauge are the easiest to read, but they are also the most expensive styles.
Beam
Not much can go awry when you use a beam torque wrench, as long as you don’t overload it and the shaft bends, or inadvertently bend the beam indicator. You’ll need to exchange the wrench if the shaft is bent.
If, however, the beam indicator is bent and doesn’t read zero when the wrench has no load, all you need to do is bend the indicator so that the zero on the scale lines up with the pointer at the end.
If you’re using a beam style wrench to tighten a fastener, you have to look at the pointer on the scale straight. Otherwise, you won’t read the indicator properly. By viewing the pointer from a different angle, it might look like it’s slightly lower or higher than what the actual reading is.
Click Adjustable
Click adjustable torque wrenches are designed with an adjustable handle and internal spring. If you twist the handle, it modifies the wrench’s torque value. While tightening a fastener, the wrench will make a “click” sound and slip slightly once you’ve hit the preset torque value. This is designed to prevent you from applying too much torque. The benefit of this type of torque wrench is that you’re able to feel the torque and not by having to take the time to view the gauge or scale.
Once you’re done using an adjustable click wrench, always reset the torque setting back to zero. By doing this, you’ll relieve the pressure on the internal spring, so it doesn’t take a set and create inaccurate readings in future use.
Digital Electronic and Dial Gauge
Digital electronic and dial gauge torque wrenches feature gauges that are easy to read and are usually the most precise. Because of how accurate they are, they are also the most expensive torque wrenches; their price ranges from several hundred dollars to several thousand. These are precision tools and need to be handled carefully.
Unless you’re working on a NASCAR engine or some other professional performance engines, a digital or dial gauge torque wrench is more of a nice to have than a need.
How to Use a Torque Wrench
The first thing that you need to do is find the fastener’s torque specifications. If you don’t know what the specifications are, don’t guess. Instead, find it up in a service manual or online. Remember that any torque values that you find specified on the majority of fasteners are meant for clean, undamaged, and dry threads.
The loading that you apply to the bolt is dependent on the amount of friction that will be created by the threads when the fastener is being tightened. If you lubricate or oil the threads, it will decrease the amount of friction and raise the amount of applied load. This might overload the bolt, which increases the threat of breaking or stretching the bolt. So, with this being said, you should always check to see if a bolt should be lubricated or not.
When you are tightening a nut or bolt, start by using an ordinary socket or wrench to get the bolt or nut tightened to where it’s firm but not too tight. Then tighten it to final specifications with your torque wrench.