What is it for and how to choose the best torque wrench for your garage
Have you ever overtightened something and stripped the threads or broken the bolt while servicing the vehicle? Or, you tightened something only to loosen it soon after? If so, you probably didn’t apply the right amount of torque. Here’s everything you need to know about torque wrenches and how to use them.
What is a torque wrench and how does it work?
Car and Driver tells us that “torque is a twisting force”. Foot-pounds (ft-lb or lb-ft) and inch-pounds (in-lb) are the most commonly used units for measuring torque in the United States. It is measured by the force (pounds) applied to a lever (measured in inches or feet) used to turn a fastener. A torque wrench measures torque and relays this information to the user via a needle and scale, an audible or tactile click, or on a digital readout.
What are the most common types?
According to Car and Driver, the most common are “beam or deflection, dial indicator, clicker and digital” styles. Deflection type torque wrenches are durable and inexpensive but often difficult to read accurately and exhibit the ability to apply too much torque.
Digital styles are easy to use but are more delicate and use replaceable or rechargeable batteries that might be dead when you need them most. Clicker styles are durable, precise, and provide positive feedback when applying the set torque value, even if you cannot see the scale. However, adjusting the torque value by turning the handle requires grip strength and good eyesight.
How to use a torque wrench
The Home Depot provides detailed instructions for using each type of torque wrench. Generally, the first step is to determine the amount of torque to apply. This information is available in service manuals or online. Next, you will need to select a torque wrench that allows the required value to fall between 20% and 80% of its range for best results. Then, using the appropriate socket, apply gentle, even pressure to the torque wrench handle until the desired torque is achieved.
What is the difference between a torque wrench and a ratchet?
The difference between a torque wrench and a ratchet is in their intended uses. A ratchet can quickly tighten and loosen bolts and nuts when assembling or disassembling all things bolted together. A ratchet does not measure torque, and its internal components withstand more abuse. On the other hand, torque wrenches accurately apply torque when tightening nuts and bolts and are not intended for loosening bolted connections or quickly tightening fasteners.
How to choose the best option
BobVila.com recommends considering the following factors when choosing the best option:
- Accuracy – Medium keys have an accuracy range of plus or minus 4%. A smaller range indicates a higher quality tool but is not always necessary.
- Drive Size – A torque wrench works with standard sockets with drive sizes such as quarter-inch, three-eighths-inch, half-inch, three-quarters-inch, or larger. Having a quarter-inch drive and a half-inch drive in your toolbox will accomplish most DIY mechanical tasks.
- Range – Smaller ones have lower torque ranges, often measured in inch-pounds. They are handy for small fasteners in tricky assemblies. A half-inch drive should be between 20 lb-ft and 150 lb-ft, making them useful for torque up to 120 lb-ft. Higher torque values require larger torque wrenches.
- Scale readability – Different types have different scale styles. Before buying a new one, make sure you can read the scale quickly and easily. Applying the wrong torque value because of a misread scale renders its use useless.
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