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Last updated on January 19th, 2021
When you need to fasten a bolt or nut or any other fastener you can use a variety of tools including a spanner, ratchet, wrench or any other appropriate tool. The challenge with most of these fastening tools is the difficulty to control the amount of torque applied on a fastener. As a result, you may end up with under tightened or overtightened nuts and bolts, which can be catastrophic. This is where a torque wrench comes in handy.
A torque wrench is a tool for tightening bolts, nuts, and other fasteners to a specific torque value. If you do not know what torque is, it is the amount of force required to cause an object to rotate about an axis. It is also known as moment or the turning effect and its units are Newton-meter (Nm) or pound-foot(lb-ft). This turning effect is what makes fasteners thread in and create a clamping force. In other words, in fasteners installation, torque is the tensile force or preload created in fasteners. This tensile force creates a clamping force that helps hold the two mating parts together without failure.
How to calculate torque
You can calculate the appropriate torque value for your specific application using the classic torque equation, T = KDP. Where T represents the target torque, K is the coefficient of friction, D is the nominal diameter of the bolt, and P is the preload or the desired tensile load on the fastener. However, much as this equation is accurate, it might not provide an optimal torque value. As such, rigorous tests are usually performed in addition to torque calculation. Tests help to account for other variables such as dynamic friction, run-down speed, and part tolerances that are not taken care of in the equation. Most manufacturers use the latter method to come up with torque specifications for their products.
How are torque wrenches classified?
You can use a torque wrench for various tasks ranging from DIY home activities to professional automotive and construction applications. Basically, where a nut, bolt, or screw is involved, the use of a torque wrench is inevitable. These precision fastening tools are available in various shapes, designs, and sizes. However, their major difference is in their torque rating, reading mechanism, and operation mechanism. The size of a torque wrench is primarily determined by its application. Torque wrenches for light-duty applications have a small form factor while heavy-duty application torque wrenches are big and have high torque ratings. As far as the operating mechanism is concerned, some torque wrenches require manual ratcheting while others like the new Milwaukee digital torque wrench have a motor for turning fasteners automatically. Concerning the setting of torque value, torque wrenches can be classified as either digital electronic, dial gauge, click adjustable, or bream type.
How to use a manual torque wrench
The operation of most torque wrenches involves two steps. First, you set the torque value, then you tighten down the fastener. If you are using the most common torque wrench, the click adjustable torque wrench, you will first adjust the handle in order to set the appropriate torque value. To do this, loosen the lock nut on the top side and rotate the handle to the right torque spec. Once you set the value, tighten down the locknut to prevent the torque specification from changing while you work. Then, attach the appropriate socket to the drive and begin turning the nut, bolt, screw or whatever you want to fasten. Turn in a clockwise direction until you hear a clicking sound. Other torque wrenches will indicate when the predetermined torque is reached by either lighting (for the electronic digital ones), or a sound for other types, or both. Once you are done, return the torque setting to zero and store the wrench in a safe place. Remember, periodic calibration of the torque wrench is recommended so the torque wrench remains accurate.
How to use a digital torque wrench
Digital torque wrenches are easy to set. All you need to do is input the torque value, attach the appropriate wrench socket then ratchet to tighten. In contrast, automatic torque wrenches are the easiest to use since no manual turning is needed. All you do is set the foot-pounds attach the socket, and press the trigger. The battery will turn the head to tighten down the fasteners until the appropriate torque value is reached. The downside however of a battery powered torque wrench is the price. These smart torque wrenches are often more expensive than the manual ones.
Is a torque wrench important?
One of the most common questions I get from people is whether a torque wrench is really important. Most people who ask this question argue that tools such as the hand and power ratchets, impact guns, and impact drivers can tighten down nuts and bolts just as a torque wrench. As such, they feel like buying a torque wrench is a waste of money. Others think that a torque wrench can replace these other tools. But that is not true. Each tool has its own dedicated use and should be used for what it is built for.
Since this article is about the importance of a torque wrench, I have done thorough research as always and come up with these 6 important reasons why torque wrench is important. You will also understand why you should never trade it off with other fastening tools. Otherwise, you may void the warranty coverage of a product, put your life in danger, or damage a product if you do not tighten fasteners to the specifications in the repair or owner’s manual. The following are the reasons why a torque wrench is important:
6 Reasons Why a Torque Wrench is Necessary
- Prevents voiding warranty cover
Most manufacturers such as automotive manufacturers specify the torque needed to tighten threaded fasteners. Failure to develop a sufficient initial preload in the fasteners may void the warranty or insurance cover. In most warranty policies for automotive, loose fasteners are clearly stipulated as one of the reasons why warranty would be voided. It is therefore important that users keep their end on the warranty by ensuring that nuts, bolts, and fasteners are tightened to specification.
- To prevent damage
Screws, nuts, bolts, and other fasteners should not be overtightened. Doing so may cause damage to the threaded hole or the product being affixed. For example, when changing rims in automotive, a torque wrench prevents overtightening the nuts thereby protecting the rims from damage. Overtightening lug nuts could also result in warped rotors of your car. Similarly, when hooking up jumpers between your RV batteries or microgrid battery bank, a torque wrench ensures that the cable lugs are not overtightened as this could lead to damaged or broken battery terminals. Also, loose electrical connections may cause sparking that may damage the terminals or even cause a fire.
- To avert safety hazards
Loose fasteners are catastrophic, especially on moving parts. This is why manufacturers provide torque specifications to installers and assemblers. For instance, if a moving part is loosely attached, it vibrates and sometimes can come off posing serious danger. In April 2015, for instance, an American Air Force reconnaissance airplane caught fire and almost killed 27 airmen onboard simply due to a loose nut that connects the oxygen tubing. The accident caused $62.4 million in damage. Clearly, a failure to torque fasteners to specifications can cause serious safety hazards, damages, potential litigations, and sometimes death.
- Torque wrenches are versatile
You can use a torque wrench in a variety of applications ranging from small tasks at home, changing rims in the garage to fastening bolts and nuts in the construction industry. Torque wrenches also don’t cause damage since only the required, predetermined torque is applied. This means that light materials such as aluminum and others will not get dented during fastening. This fastening tool also prevents threads of fasteners from stripping out and bolt heads from snapping due to overtightening.
When you are tightening down nuts and bolts with a torque wrench, it means that you are applying only the required torque. Most of these torque wrenches have a very small margin of error and hence accuracy is guaranteed. Thus, by developing the correct preload in fasteners, safety is guaranteed. Safety, in this case, concerns the product and its users. For instance, when you apply the correct amount of torque on the lug nuts of your car wheels, you not only protect the rotors from warping but also yourself from the potential danger of a failed wheel.
- Ensures balanced rotation
A torque wrench ensures that rotating components rotate in a balanced way in relation to the axis e.g. flywheels and drive shafts. Also, torque wrenches are important in the sense that rotating components with center-locking nuts such as wheel bearing and pulleys are not over-tightened.