One of the most important tools you will use for engine repairs is the torque wrench. It will also be one of the most expensive tools you purchase. This special type of wrench allows you to properly tighten critical fasteners so that they will not come loose during engine operation. The two most common types of this tool are the “beam” type and the “click” type. Here is a description of the different types and their advantages and disadvantages.
Beam type torque wrenches are the least expensive, but can be very accurate. The beam wrench works by the beam bending in as torque is applied. This type is very simple, reliable, and accurate, and there is not much that can go wrong with it when used properly. When tightening a bolt, make sure to only apply force in the center of the handle. This allows the beam to bend in the manner it was designed to show the correct torque. Don’t over torque the wrench or the beam may bend permanently. Do not drop the wrench because rough handling can bend the pointer arm or pointer. If the pointer is bent, it can be bent back to the center without affecting accuracy. If the beam is bent it cannot be bent back.
Plus . . . Rugged and pretty easy to use. Can be used in both directions, helpful for measuring "breakaway" torque when disassembling a fastener.
Minus . . . You have to watch the dial as you tighten the bolt or nut. Takes a bit if getting used to.
Probably the most common type of torque wrench seen is the “click” type. The click type has a dial that you turn to set the torque. As you tighten the fastener, when you reach the correct torque the wrench “releases” slightly, making a clicking sound at the same time. Click type torque wrenches should not be used to loosen fasteners. It is also a good idea to turn them down to the lowest setting when you put them back in your tool box. This prevents the internal spring from weakening and affecting the torque reading.
Plus . . . Very easy to use. No need to watch anything while you tighten a bolt or nut.
Minus . . . . A little more delicate. You absolutely should turn the wrench back to “zero” after use or it can lose its accuracy.
The newest type of wrench is the electronic digital torque wrench that has electronic sensors to measure the torque. They typically have a digital readout and also will “beep” when the correct torque is reached. Some of these wrenches also have the capability of measuring the degrees of rotation of the wrench, which is needed when tightening fasteners on many late model vehicles.
Plus . . . very accurate. Does away with needing a separate angle gauge for newer engines that use the “torque plus angle” method of tightening.
Minus . . . needs a battery or maybe two. Probably delicate compared to the other styles.
The dial type is a variation of the beam type but uses an actual gauge type dial to show the torque applied. It is not seen very often.
Plus . . can also be used in both directions to measure "breakaway" torque when disassembling a fastener.
Minus . . requires watching the dial as you use the wrench.
Torque wrenches are most accurate in the center part of their range. You may need several different ones to properly torque all of the fasteners in the average engine. For instance, a ½” drive torque wrench that measures torque from 20 to 250 lb ft will not be very accurate at very low settings. It would be best to have a smaller wrench that covers the range from 15 to 80 lb ft and then a second one that goes from 50 to 200 lb ft or so. I actually have four different ones in my tool box.
Torque wrenches are precision tools. Treat them gently. Never use a torque wrench to loosen bolts except when using a beam or dial type to measure breakaway torque. Always turn the torque setting back to "zero" or less on adjustable, click type wrenches. This will release the pressure on the internal spring and will keep the wrench accurate for a longer time. If you use a torque wrench on a daily basis or very often, it should be at least checked for calibration on a regular basis. If you question the calibration of your torque wrench, compare it to another one. This will give you some idea if it is badly out of calibration.
Take care of your torque wrench and it should last a lifetime.