How a Torque Wrench Works

We live in an amazing world and time, wouldn’t you agree? With cars that drive themselves to delivery by drone, civilization has advanced in so many ways that you can’t keep count. 

However, there are still a few things that should or need to be done by hand, such as using a torque wrench. 

Whether it’s tightening the lug nuts that secure the tire and rim on your car or replacing the head bolts due to a blown head gasket, a torque wrench is a necessity for any weekend mechanic and for professional mechanics as well. 

If you are wondering whether you really need a torque wrench or if you just want to understand how this tool works, this article should fill in everything you want or need to know about torque wrenches. 

How Does a Torque Wrench Work?

A torque wrench is designed to let you know exactly how much “pressure” or torque is being applied to a fastener. While this amount will vary depending on the length of the handle and the amount of force you use, a torque wrench will detect how much torque (which is measured in feet per pound) you are applying and show the number of foot-pounds on a dial or meter. 

Different Types of Torque Wrenches

Torque wrenches come in different sizes and designs. The four main types of torque wrenches include: 

  • Slip Style– This torque wrench works by losing its grip after reaching the set number of foot-pounds you have indicated that you want. While this type of torque wrench prevents you from overtightening a fastener, you can’t see how much torque you have already applied. 
  • Digital Style– As the name implies, digital torque wrenches have an electronic digital readout to let you know how much torque you have already applied and when you have reached the desired amount. Most digital torque wrenches today use a beeping tone, a buzzer, or a flashing light to alert you that you have reached the desired foot-pounds. These tend to be the most expensive models, but many people find this tool highly desirable. 
  • Click Style– The click style is perhaps the most common type of torque wrench you will see. Once you have reached your desired level of torque, the tool gives off a very audible click sound. Since these are relatively inexpensive and very easy to use, it’s no wonder that this style is often used by both home mechanics and professionals alike. 
  • Beam or Dial Style– The beam or dial type of torque wrench was once the perennial favorite. On the top of the torque wrench itself is a long beam, which ends in a pointer on a dial. Like reading a scale in the supermarket, the pointer will indicate how many foot-pounds have been applied. This type of torque wrench requires attention, however, since it will not notify you with a click or a beep. Some people may find this style difficult to read. 

There are larger styles of torque wrenches, but these are often used for other applications, such as plumbing, and you won’t find them in most homes or mechanic repair shops

Torque Wrench Sizes

As with ratchets and sockets, torque wrenches come in different sizes AKA drives. 

  • 3/8-Inch Drive: For most people, this is the smallest torque wrench you will purchase. This is the most common drive size for automotive work. 
  • ½-Inch Drive: If you have a larger vehicle, such as a ¾ ton truck, the ½ inch drive is commonly used by both home mechanics and professional mechanics as well. This size lug wrench works well for lug nuts or the suspension. 
  • ¾ and 1Inch Drive: You probably won’t need a torque wrench this large, but these are common in mechanics shops where they work on construction vehicles or large semi-trucks, such as Mack trucks. 

FAQ Regarding Torque Wrenches

  1. Can torque wrenches be used to loosen bolts?

A: Yes, they can, but it really isn’t recommended. The counterclockwise turning of the wrench can upset its calibration. However, if you are stuck and have no other option, of course, the torque wrench will loosen a bolt or nut. 

  1. Do I Really Need a Torque Wrench? 

A: Before the invention of the torque wrench in 1918, of course, mechanics, plumbers, and others got by without one, but chances are that some items were damaged in the process or they simply came off. 

If you think that you did just fine, changing your tire by the side of the road using a lug wrench, it’s true that you might have tightened it sufficiently to prevent the wheel from falling off, but you also could have stripped the threads, but if you have a torque wrench, why not use it and do things correctly? If a torque wrench didn’t make a difference, the manufacturer would not have bothered to put specifications in the repair manual. 

  1. Do Torque Wrenches Need to be Recalibrated?

A: Yes. Nearly all torque wrenches will need to be recalibrated approximately once each year, or about every 5,000 uses. Since you most likely are not keeping track of how often you use your torque wrench, once a year is a good rule of thumb. How you calibrate a torque wrench will depend on the type you purchase or own. Check with the owner’s manual for instructions. 

The Bottom Line

Torque wrenches are quite important for accuracy when doing automotive work, plumbing jobs, or other types of mechanical work. Even back yard mechanics can benefit tremendously from a good working torque wrench. 

Once you know that you can tighten the nuts and bolts on your vehicle with precise accuracy, you will never again settle for a plain old lug wrench ever again. 


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