A torque wrench is essentially a tightening tool for shoulder screws, hex head bolts and nuts to a precise torque value to avoid over-tightening which can break the bolt or under-tighten making equipment liable to fall apart. The torque itself is a measure of the force required to rotate an object, where the axis around which the object rotates represents the pivot. Here we discuss how to use the torque wrench effectively for budding DIYers to avoid disasters.
Types of Torque Wrenches
From basic home repairs to large scale industries like automotive, construction, and maintenance. Whether it is to fasten screws and bolts or estimate the pressure applied to fasteners, wrenches are an indispensable tool in many industries.
A variety of wrenches specialized for specific skill sets are used, some of the most common ones are:
Electronic Torque Wrenches- These work by using an electric sensor to determine the twisting force applied and these readings can be saved and accessed through a computer at a later date.
Beam- This features a handle to apply force with a scale to display the level of torque applied. This inexpensive tool can also be used for tightening and loosening.
Click- A click torque wrench makes an audible click sound due to a spring-loaded lever breaking on reaching the required torque level.
Hydraulic Torque Wrenches– As the name suggests, this industrial-use torque uses hydraulic parts and hydraulic seals to reach the torque level.
Micrometer Torque Wrenches– Widely used to measure load weight in cargo transportation like in trains, ships, and planes as this directly affects the freight. Miscalculation can endanger crew and passengers’ safety.
Dial Torque Wrenches- Widely used in automotive, aerospace, and defense industries owing to their high degree of accuracy.
How Torque Wrenches Work
Torque that is applied on the fastener depends on the force applied on the handle and the length of the handle, hence torque is calculated as force x length. The handle is connected to an indicator that connects to a calibrated scale ( lb·ft/pound-foot, lb·in/pound inch, or N·m/newton meter) which will direct you when to stop twisting the bolt.
Torque Wrench Settings
Studies show that most DIYers who don’t use a torque wrench set to end up overtightening leading to broken bolts and damaged equipment. However, with the manufacturer listed setting, you will be applying just the correct amount of force and will be alerted when you reach the required torque.
Torque Wrench Use and Care Tips
Proper use will ensure long-lasting use of your torque as well as effective results when using the tool.
- Two- steps fasteners tightening—begin till you reach half the torque and then fasten until final torque.
- Dirty or rusted threads must be cleaned before tightening, Not lubricated unless recommended by the equipment manufacturer.
- Remember that the wrench is dialed back to zero (never below zero) after finishing work.
- The torque wrench is NOT a breaker bar—using it as such will destroy the torque mechanism.
- Use kid gloves when carrying it—since the accuracy can be affected by up to 30 percent by a fall which will require recalibration before using it again.
What to Look for in the Torque Wrench Set
It is important to choose the correct wrench for the type of work you are doing to make the most out of your tool. Here is what to look for individual types of wrenches.
Pro-quality clicker-style micrometer wrench set- A pro-quality wrench may strain your wallet but is worth the buy as its calibration lasts longer. They also come with a warranty and many can be repaired and recalibrated after the warranty period expires.
Bending beam torque wrench set- aka deflecting beam provides lifetime calibration if not dropped. However, since the reading needs to be taken directly above the needle, this makes it difficult to use it in close quarters or at an angle.
Economy clicker-style torque wrench sets- These work best for single tightening projects. Unfortunately, their calibration is temporary and calibration services don’t usually recalibrate them, making it a disposable, single project tool.
Bending beam, clicker style, digital and dual beam are the most common torque wrenches. Dual beam and digital wrenches tend to be expensive ranging from $200 to $400 and are preferred by professionals rather than DIYers. With correct usage tips, any of these wrenches can be used to torque nuts and bolts.
Torque Wrench Calibration
Regular calibrations are a part of the maintenance of torque wrenches to provide accurate results during use. Calibration is a procedure used to measure the accuracy of measuring tools, align and adjust the tool according to the international standards applicable. The accuracy of a tool deteriorates with time and use, hence the need for calibration thus newer wrenches provide more accurate measurements. If not recalibrated, the tool may exceed the calibration error of 5% leading to wrong measurements and product failure.
For best results, calibrations are done professionally at accredited laboratories. For recalibrations of used tools, the rule of thumb is to recalibrate every 2,500 repetitions for frequently used tools or once per year for infrequent users.
Setting a Torque Wrench
Refer to the owner’s manual or shop manual to set the torque wrench to one-half the torque specific standards. Contrary to popular belief ‘tighter is not better’. An over-tightened lug nut causes warped rotors which increase stopping distance and in other cases leads to broken wheel studs.
Use your hands to spin the lug nuts. Don’t lubricate the stud. The jack is lowered such that the tire is just in contact with the road. Each nut is tightened to half the given torque than to full torque once the vehicle is lowered completely.
Tightening Patterns
Once the proper torque is locked in then each nut is tightened in sequence.
There are two ways:
- Bolts in circular patterns, such as the lug nuts on wheels, are tightened in a starfish or criss cross pattern.
- Cylinder heads which are usually larger, oblong are tightened specific sequence, beginning near the middle then circling.
Know the Bolts
Bolt heads have markings that indicate its strength class. Refrain from using an ungraded or unmarked bolt on more highly stressed materials. SAE Grade 5/DIN 8.8 bolts can be safely used in most cases, while SAE Grade 8/DIN 10.9 bolts are higher-strength fasteners used in suspension parts and connecting rods. Unique markings are usually reserved for specialty fasteners with a specific use.
Conclusion
Knowing your torque wrench and using it correctly will help it last longer and avoid disasters like broken wheel studs and damaged equipment. Follow the user manual when in doubt and remember to recalibrate when necessary to ensure a long-lasting tool in your arsenal.