Getting the Best Out of Your Torque Wrench
A lot depends on accurate torque wrench measurements, and your ability to use your wrench effectively depends entirely on how accurate it is. Since having accurate torque wrench measurements is so crucial, it’s important to know the best ways to improve and maximize force measurement.
Proper Factory Calibration
This is the crucial first step and if this is not right nothing else can be. Look for wrenches that are guaranteed to within +-5% accuracy or better. They should also be calibrated at different points to help guarantee accuracy in all ranges. Good torque wrenches ought to come with a factory certificate of calibration, as well.
Calibration and Materials
If you want to guarantee your torque wrench measurements, it’s wise to invest in a quality wrench. Cheaper wrenches will be made with a lot of plastic, but metal is both more durable and easier to keep calibrated.
There are specific things you can do as you use torque wrenches that will help to guarantee accurate torque wrench measurements, but before you consider those you need to cover all your bases. This means occasional recalibration based on the schedule recommended by the manufacturer, storing your torque wrench in the recommended way, and always rechecking calibration whenever it gets dropped.
Maximize Your Accuracy During Use
All the factory calibration in the world won’t help if you’re not using it right, so don’t forget these four things:
- Look carefully before you start. Double check exactly where you set the dial. Don’t assume you did it right: check.
- Pay attention to the conditions of calibration. If you’re being asked to specify an 80 ft-lb torque on a fastener that’s completely dry, you should assume you won’t get this accurately if the fastener is wet or greasy. Judge carefully whether the conditions are close enough, and don’t be afraid to put things aside until they are.
- Make sure to turn the wrench slowly and steadily. This should be a no-brainer, but a surprising number of people swing their torque wrench around and fly right past the click that indicates they’ve reached load. Don’t be this person.
- Always push only on the handle of your torque wrench. If you want accurate torque wrench measurements, then always use the handle only. The wrench is measuring force at the pivot point and that’s where it’s been calibrated. It will only show on the scale when you apply pressure on the handle.
Understand the Science
Torque is a type of rotational force, and this forces compressed whatever material you are fastening as the wrench is spun around. As the torque wrench applies this force, the materials being fastened will push back. This push back combined with the torque force creates friction, and this friction makes the fastener increasingly more difficult to turn. This turning difficulty is what the wrench is measuring. Naturally, you can only get accurate torque wrench measurements if conditions are exactly what the torque wrench is assuming. Friction will depend on temperature, materials, faster shape, and surface coatings. If these factors don’t match your specifications, you’ll get an inaccurate measurement.
Accurate torque wrench measurements are the only way to guarantee you don’t accidentally overload a fastener, which can cause it to weaken and break, or under-load it, which can cause a mechanical failure. For any measurement device, accuracy is critical. Make sure your torque wrench measurements are always accurate by getting a good one, keeping it calibrated, and using it correctly.