How Does a Torque Wrench Work

By Richard S. Clark | Last Updated: September 9, 2022

A torque wrench is a unique tool used in auto mechanics and construction tasks. After calibrating the device, you can easily determine the rotational force or torque. The torque is needed so you will know how much effort is required to tighten a nut or bolt. Putting too much pressure and excessively tightening the nuts or bolts can damage the thread.

Knowing the right force to apply, can fasten a bolt with less effort as compared to standard wrenches. Some think that the tool is not required, but most new mechanics tend to overtighten everything. Overtightening might affect the functionality of the equipment and can damage the bolts and threads.

How Do Torque Wrenches Work?

When it comes to tightening nuts or bolts, the best tool to use is a torque wrench. One reason is that you can calibrate it to apply the needed amount of pressure. The torque amount will depend on the amount of force you need to use on the handle and the tool’s total length. In calculating the torque, multiply the force by the length of the wrench.

For example, your tool’s length is one-foot long, and you need 40 pounds of force on the handle, which means you will need 40-ft lbs of torque to tighten the nuts. If in case your torque wrench is 2-feet long, you need to apply 40-lbs of force. The bigger torque wrench will increase the leveraging effect to multiple the torque. In this case, it means that you need to use 80 ft-lbs of torque.

The above computation will determine how much load is applied to a fastener using a calibrated torque wrench. A scale on the wrench will display how much load you are applying. The scale is read at inch-pounds, foot-pounds, or Newton-meters.

Torque Wrench Maintenance

The torque wrench needs to maintain its accuracy. Checking the tool periodically for defective parts or wear is a must. A well-structured maintenance program will boost the tool’s performance and lessens untimely downtime. Thus, you can save time and money.

1. Monitor Number of Cycles

If you are using the tool every day, it will surely wear faster and go out of calibration. Its accuracy is reduced and will be less helpful in tightening the bolts. Taking note of the number of cycles per day you used the torque wrench is the most accurate way to determine the best interval for maintenance.

It is recommended that the tool should be used no longer than 100,000 cycles. Also, when notice accumulated dry or old grease, unstable or loose parts, or components that display signs of excessive wear.

2. Check the Wrench Ratchet

Inspect the wrench ratchet regularly for any wear. Cleaning and lubricating it can help it last longer. The ratchet screws should be tight enough and spin smoothly when turned.

3. Examine the Wrench Handle Regularly

Make sure the wrench handle is free of corrosion and should not wiggle when used. If you failed to check, lubricate, replace worn components, and adjust can result in premature failure.

4. Store Wrench Properly

Keep your tool protected from chemicals, dust, grime, and other hazards by putting it in the right place when not in use. Make sure the storage area is dry and clean. Before storing it, do not forget to clean the wrench’s external parts using a clean, dry cloth.

5. Clean the External and Internal Parts

Cleaning fluid or other chemical solvents may corrode the torque wrench internal parts of the tool that can cause premature failure. If needed, you can dismantle the device following the manufacturer’s instructions, or you can bring it to a reliable technician.

6. Return to Minimal Scale Value After Use

The majority of torque wrenches are designed with an internal spring mechanism. An adjustable wrench must pass a linear capability test. It is a must that you turn it back to a minimum scale value after use. This will help maintain the linearity of the spring and wrench calibration.

Before storing the wrench, make sure that it is at the minimum setting. A calibrated torque wrench uses a spring with an identified linear range. It has been proven that if you leave the wrench calibrated at one setting, it greatly affects the spring linearity. Resulting in inaccurate use in other settings.

It seldom happens, but linearity can be affected, which results in errors. It’s because of this why it is recommended to return it to its minimum setting before storing. If your wrench has only one set, you can consider presetting it. It has no scale and is set by a torque tester—no need to adjust it to a minimum and remain at one torque setting.

It’s a must to ensure that the torque wrench is in good condition, so it should be maintained and treated well.

Types of Torque Wrenches

How the torque wrench work will also depend on the type of wrenches you have. Digital electronic, click adjustable, beam style, and dial gauge are the four basic torque wrenches. The cheapest among the four is the beam style at $30 or less.

Professional technicians commonly use an adjustable click torque wrench because of its accuracy. If you prefer the one that is easy to read, buy the dial gauge and the digital electronic, but you need a bigger budget as it cost more than others.

Beam

The beam torque wrench requires proper handling as overloading it and bending the shaft or unintentionally bend the beam indicator can make this tool useless. You need to buy one if the shaft bends.

If the beam indicator bends and the reading is not zero when not in use, you can bend the indicator so it will return to zero.

If you are using this type of wrench to tighten a fastener, you need to check at the scale’s pointer. Make sure it is straight, or else it will not read the indicator properly. If you view the pointer at a different angle, you might find it slightly lower or higher than the actual reading.

Click Adjustable

The click adjustable torque wrench has an internal spring and an adjustable handle. Turning the handle changes the torque value. As you tighten the fastener, it will produce a clicking sound, and if you hit the preset torque value, it will slip a bit. It is designed this way to prevent using too much torque.

The main advantage of this type is that you can feel the torque to know when to stop. Unlike others, you need to check the gauge or scale from time to time.

After using, do not forget to set it back to zero. This will relieve the pressure on the internal spring and continue to provide accurate readings.

Digital Electronic and Dial Gauge

If you are looking for easy-to-read and accurate torque wrenches, invest in digital electronic or dial gauge wrenches. As you know by now, these two are the most expensive types of wrenches. The price may range from several hundred dollars to thousands. These tools require careful handling, as dropping them may affect their accuracy.

Other Types of Torque Wrenches

Slipper

This type of torque wrenches has a roller and cam. The cam is connected to the driving head while the roller pushes the cam to lock it in position. Force is applied provided by a spring. The wrench will slip and release the torque applied to the bolt. This type of wrench will not overtighten the fastener.

No Hub Torque Wrench

Plumbers use this type of torque wrench in tightening the clamping bands on pipe couplings without a hub. It is a T-handled wrench with a one-way clutch and ratchet combination. The tool is preset to a fixed torque enough to secure the coupling.

Deflecting Beam

The deflecting beam torque wrench applies the principle of adding torque to a deflecting beam rather than a coil spring. It helps extend the accuracy of the tool longer that is safe even on maximum loading. The tool provides accurate reading and produces a clicking sound if it reached the tightness required. It also displays when the needed torque is achieved.

Conclusion

A torque wrench is a must-have tool, particularly for car owners. Tightening nuts or bolts is not an easy job, but thanks to this tool, no need to call an expert to deal with the loosen nuts and bolts. How to use the device and its function will depend on the type of wrench you are using. Some wrenches are easy to use and do not require an expert to use them. Others have complicated functions that you can learn from experts. If you think you cannot handle the task even if you have the tool, you can call a professional to help you.

Resource:

40 Different Types of Wrenches and Their Uses

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