What is torque?
Torque is a turning or twisting force used to create tension on a fastener. Turning a nut on a bolt, for instance, moves the nut down the bolt’s threads. As the nut reaches the surface separating it from the head of the bolt, any additional torque applied squeezes the surface between the nut and the bolt’s head, creating tension.
How do you measure torque?
Torque is measured by multiplying the amount of force applied by the distance between the point where the force is created and the point where it is applied. For example, if you apply 10 lbs. of force with a 2-foot torque wrench, you’re applying 20 lbf.ft of torque to your fastener.
How much torque do I need to apply?
It depends on your application. Large nuts and bolts sometimes require hundreds of lbf.ft of torque to hold properly. Certain small fasteners require amounts of torque measured in ozf.in. The manufacturer of the fasteners you’re using should provide information on appropriate torque values. However, the actual amount will vary depending on the nature of your application and your substrate. If no information is available, the only way to find out is to develop your own set of torque values based on controlled trials.
What happens if you don’t apply the correct torque?
Two things can happen:
- If you don’t apply enough torque, your fastener can back out. This will increase pressure on other fasteners or allow your assembly to come apart under stress. It also creates a potential hazard, as the loose fastener can damage the surrounding area.
- If you apply too much torque, you risk warping, deforming, or otherwise weakening your fastener. A weakened fastener is more likely to shear or break under stress, increasing pressure on other fasteners and potentially causing assembly failure. The broken fastener, once loose, can damage nearby objects.
How do you make sure you apply the right amount of torque?
The best way to be sure you’re applying the right amount of torque is to use a torque sensitive tool to apply force, then to test your fastener afterward. Torque tools will either inform their operator when the appropriate torque is reached so they can stop applying force, or they mechanically prevent too much torque from being applied. Even with the best tools, mistakes can still occasionally occur. It’s therefore important to test the torque applied to your fasteners for quality assurance. Testing can be done with a torque tester, torque sensor, electronic wrench, or dial measuring tool. Alternatively, automated applications often employ built-in screw counters or control systems for quality assurance.
What’s the best torque tool for my application?
Again, it varies depending on your application. First, figure out your needs. The right tool for your assembly depends on the amount of torque you need, your margin for error, the speed of your assembly, and any special needs like clean room certification or electrostatic discharge protection. Then, select the tool that best fulfills your requirements.
Generally speaking, hand tools are slower but reliable and inexpensive. Electric tools are fast and versatile but cost more. Pneumatic tools deliver more torque and are less expensive than electric tools, but they require extra equipment, such as air compressors and hose lays.
To help narrow down your options, try our torque tool selector or ask one of our torque experts.
Can the same tool be used to deliver different amounts of torque?
Yes. Each torque tool has a specified range of torque values it can deliver. Some tools are easily adjustable from the outside. Others must be adjusted internally and may require extra equipment, such as a torque tester.
How do I know if my tools are in calibration?
Regular testing is the best way to know if your torque tools are properly calibrated. This can be accomplished by using a torque tester in-house, or by shipping your tools to a certified service center.
How often do torque tools need to be calibrated?
As a baseline, calibration should be tested every six months or 100,000 cycles, whichever comes first. For more critical applications, calibration should be checked weekly or even daily. If a tool is found to be out of calibration, it should be removed from service until it is recalibrated. It should also be flagged and, in the future, should be tested twice as often as normal.
The tools I use deliver high amounts of torque and put stress on my operator’s wrists. Is there a way to reduce this impact and protect my workers?
Torque reaction is a common problem when using tools which deliver high amounts of torque. Air tools, in particular, often deliver enough torque to cause injuries to operators over time. Torque arms are used to counteract this reaction. These arms hold the tool in suspension, taking the weight off the operator’s arms, and absorb the torque reaction, preventing operator injury.
Can torque tools be automated?
Yes. Torque tools are commonly automated to increase speed and reliability. In order to ensure that quality standards are maintained, automated wrenches and screwdrivers are often coupled with screw counters or DC control units. These quality assurance tools track omissions, cross-threading, unfinished rundowns, and other performance data. Doing so makes sure that standards are met even in the absence of direct human oversight.
What’s the difference between air tools and pulse tools?
All pulse tools are air tools; not all air tools are pulse tools. Both use compressed air to apply force to fasteners. Air tools apply a continuous amount of force until the right torque has been applied. Pulse tools apply torque in a series of rapid bursts until the correct torque level is attained. Air tools are more accurate, but they create more torque reaction. Pulse tools are slightly less accurate, but they deliver less torque reaction, allowing them to apply more overall torque.
I’m making delicate electronics. Is there a way to prevent damage to my components from electrostatic discharge coming from a torque tool?
Yes. Certain torque tools are specifically designed to prevent electrostatic discharge from damaging electronic components. These tools are essential in assemblies where ESD is a common issue.
My torque wrench is broken. What do I do?
The simple answer is that you need to take your torque wrench out of service until you can repair or replace it. Using a broken or damaged tool can harm your operator, your product, or your other equipment. After all, if you’re using torque tools, you’re using them for a reason. The safety and reliability of your products depends on the torque applied to their fasteners.
To fix the problem, send the defective tool to a certified service center for repair. The standards the service center must meet can be found in the regulations applicable to your product or industry. For example, if you work in the automotive industry, your torque tools must be repaired under the standards referenced in the U.S. Department of Transportation code of regulations.
How do I eliminate electrostatic discharge?
The best way to prevent electrostatic discharge is by stopping potential from building in the first place. While it’s not possible to entirely neutralize every source of electrical charge in a working manufacturing plant, you can reduce the potential by following a few best practices:
- Keep electronic equipment away from blowing air, as it increases electric accumulation. As such, any electronics assembly should be separated from fans and HVAC systems, and electronics should not be cleaned with compressed air.
- Keep electronics away from plastics and other synthetic materials which accumulate electric charges.
- Install a grounding system designed for low voltage dissipation.
- Treat floors, especially carpets and rugs, with anti-static compounds. Remove carpets and rugs where possible.
In addition to following these guidelines, consider investing in equipment which is helpful for reducing electrostatic discharge.
How do I safely use and maintain a pneumatic screwdriver?
After you have located your tool and your workstation, follow these steps to get ready for usage:
- Select a bit.
- Select your level of torque.
- Attach the air hose.
- Select forward or reverse motion, if this is an option on your tool.
- Securely holding the tool, place your bit on the fastener.
- Activate your tool by squeezing the lever or trigger, or by pushing your tool against the fastener.
How much do torque wrench calibration services cost?
There are two ways to calibrate your torque tools:
- Send your tools to a certified service center
- Invest in equipment and training to establish an in-house service center
The advantages of sending your tools to a service center include a lower initial cost and guaranteed quality. The disadvantages are longer turnaround times and a higher cost of service per tool.
If you establish your own service center, on the other hand, you can enjoy rapid turnaround times and a lower cost of repair per tool. However, the initial investment is higher and it adds complexity to your operation. Also, unless your operation has a large number of tools, your in-house service center will suffer from excess, unused capacity, a cost with no benefit.
Did we answer your question? If there’s anything else you’d like to know about torque tools, just ask one of our torque experts. To see our catalog of products, download our brochure.