If you “Refer” to it, shouldn’t it be calibrated?
You'd be hard pressed to find a well-stocked toolbox that didn't have a torque wrench. This useful tool is a go-to for the DIY handyman and the professional machinist alike. They're constantly used by auto mechanics or machinery repair professionals. Anytime you need to adjust the nuts and bolts in a hard-to-reach place, a torque wrench is your friend.
What makes the torque wrench particularly useful is its ability to tighten to a specific torque. Torque is how we quantify rotational force. We use it when we swing a bat, or pedal a bike, or push someone on a swing. It's also used when turning a fastener, like tightening a screw with a screwdriver. A torque wrench can measure the tightness of a fastener, and the amount of force we must apply to turn the fastener against friction.
Certain nuts and bolts — like those on car wheels, or those on heavy machinery — need to be tightened to a specific tension. Over-tightening bolts such as these can cause damage, while under-tightening can be dangerous. A torque wrench makes it possible to create the right balance on every nut and bolt for optimum, safe function.
The first step when using a torque wrench is to set the wrench to the correct torque. You can find the right torque for a given job in an owner's manual or product manual. For instance, if you were to use a torque wrench to tighten the lug nuts on your car's wheels, you would look in your car's owner's manual.
There are three types of torque wrenches to choose from. The most basic type is called an adjustable or click-style torque wrench. These wrenches come in 1/2-inch, 3/8-inch and 1/4-inch models. You'll need to choose the right size wrench based on the job you're doing. You will adjust a click-style torque wrench by lining up the “O” with the right torque on the handle. There is a release that you can tighten at the bottom which will lock in the correct setting. This model indicates that you've reached the correct torque by making two clicking sounds.
The click-style torque wrench is simple and reliable. But, if you want to make your job even easier, you can go with a digital torque wrench. These will display your torque setting on a digital screen, so you can be certain you have it right. A “set” button lets you lock in the correct torque setting. Most digital torque wrenches will indicate that you've reached the correct torque by lighting up green. A red light means that the torque was outside of the tolerance zone.
There are also dial torque wrenches, which provide a high level of accuracy. These let you set the torque value on a dial and may use a light or a sound to indicate when you've reached the correct torque. However, some dial torque wrenches don't have these notification settings, so it's important to check the torque reading on the dial as you turn.
Torque wrenches are a precision tool. We use them when there is little room for error. Therefore, we need them to be accurate. We ensure the tool’s accuracy through regular calibration, which we will explore more soon. But the user needs to be accurate too.
To get the most precision from a torque wrench, you need to be careful from start to finish. You are setting the torque wrench with your own eyes, which means there's room for human error. It's important to look carefully at the scale head-on when you're setting it. Otherwise, you may go over or under buy a few numbers.
Well, you're using the torque wrench, turn it slowly and pay close attention. You don’t want to miss the moment that you reach the correct torque. Also, be sure that you're only pushing on the handle, not anywhere else on the wrench. The torque wrench is calibrated to measure force on the handle and nowhere else on the body. Applying force elsewhere could give an incorrect reading.
Finally, be aware of the conditions of your workspace. If you're applying torque to an especially hot or greasy bolt, it can affect your measurements. Make sure that things are dry and meet the required standards.
The whole point of using a torque wrench is to be accurate when we tighten a fastener. Naturally, regular calibration is a must for this tool. Even if you invest in a high-quality brand, you still need to keep up with calibration. High-end models may not need calibrated as often as lower-quality wrenches. However, it's still important to check the tool and be familiar with its performance history. Otherwise, you have no way of knowing whether it is providing repeatable and accurate reads.
The more often you use your torque wrench, the more frequently it needs to be calibrated. The International Organization of Standardization suggests calibrating after every 5,000 uses, or once a year. But, those numbers can be different depending on your use.
Speaking of use, remember how we emphasized the importance of applying force only to the handle? Well, if you've been using your torque wrench incorrectly, you may have overloaded the tool which can affect the accuracy. Take this as a sign to get your torque wrench calibrated before using it again.
The same is true if you have been storing your torque wrench incorrectly. These wrenches need to be stored at their lowest settings. If not, the tension spring inside the wrench, which is critical to measuring the torque load, can wear out.
Lastly, take into consideration the temperatures and conditions in which you use your torque wrench. Extreme temperatures, or using a torque wrench outside in precipitation, can cause internal rusting. This will require that a professional examine the wrench for accuracy.
A torque wrench is a go-to for scenarios that need exact force. There's no room for error in tires or expensive, industrial machines. Make sure that your torque wrenches are correctly calibrated on a regular schedule to ensure safe and accurate jobs.
Phil Wiseman is Chief Marketing Officer at Alliance Calibration. He earned a B.S. in Chemical Physics from Centre College. Phil is an ASQ Certified Quality Auditor and ASQ Certified Manager of Quality/Organizational Excellence.
If you “Refer” to it, shouldn’t it be calibrated?
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