When you get more serious about turning wrenches and working on machinery, eventually you run into items that require more finesse than “make it as tight as you can.” Some parts of an engine or other machinery deform if the proper sequence and specifications are not followed. This is where the torque wrench comes into play. These are great tools to have in your shop and this is how you use them.
Care and Storage
If your torque wrench came with a case, store it in that case. Then store the case in the tool chest or cart. A torque wrench is a precision instrument. Careless storage and handling may cause a loss of precision or even breakage. You want it to deliver consistent results and provide years of use.
It is also a good habit to unwind it and store it set at its lowest setting. Leaving tension in the wrench also leads to loss of precision.
Setting the Torque Measurement On Click Style Wrench
I have a couple of click style torque wrenches. If you look at the end near the handle, inscribed on the shaft, you see a series of numbers in two columns with some lines that point inward and then angle toward the handle. Just above those numbers, there is an inscription indicating foot pounds or Newton meters. Whichever one you see, roll the wrench over and you will likely see the other. For smaller wrenches, the measurement may be in inch pounds. The numbers for foot pounds are at intervals of 10 or 20 (for larger wrenches).
Just below the numbers on the shaft, closer to the handle, there is another series of numbers engraved around a sleeve that covers the main shaft. There is a tick mark above each number pointing along the sleeve toward the number guide on the shaft. These are numbered 0 through 9, 0 through18 for larger wrenches, or their corresponding value in Nm. These numbers represent all points in between the intervals on the shaft.
Right before the handle is the locking ring. Pull the ring toward the handle and it will spring back into a locked position when released.
To set the torque wrench, simply pull the locking ring and turn the handle with the ring against it. Rotate the handle so the numbers count up. This increases the torque measurement. For example, if I want to set the wrench to 43 ft lbs, I pull the ring and turn the handle full turns until the edge of the sleeve reaches 40 ft lbs. Then I look closely and when the tick mark above the “3” lines up with the foot pounds gauge, I release the locking ring.
The wrench is now ready to tighten the bolt to the 43 ft lbs specification.
Torqueing the Fastener
When installing the bolt, tighten by hand until the bolt is snug. If your hand won’t fit into the workspace, use whatever wrench that does fit. However, do not fully tighten the bolt. If you make it too tight, you risk over tightening the bolt before the torque wrench can be used. The torque wrench is used for the final tightening of the bolt.
To tighten the bolt to the torque spec, put the wrench in place and begin to apply steady pressure to turn the bolt. Gradually increase the pressure. When you reach the proper amount of torque, you hear a click and feel the torque wrench give way slightly. On some wrenches, this is very subtle. I know it is on my wrenches. If the wrench does not indicate, ratchet it back a few clicks and repeat. Just go slowly and really try to feel what is happening with your tools.
Once you feel the click, you are done. You tightened the bolt to spec. Just remember, attaching a part to the proper torque spec may be a multistep process. Follow the directions and sequences supplied by the manufacturer.
Drive Beam or Drive Needle Torque Wrenches
If you are using a drive beam style torque wrench there are no settings to dial in. When you see one, you may think this is what your grandfather uses. However, many people still swear by these wrenches.
At one end is the drive head where you attach your socket. From there, extends two objects. One is the pointer and the other is flexible drive beam. An indicator gauge and handle are attached to the drive beam. When torqueing your fastener, simply apply pressure to the drive beam handle. As it flexes, watch the numbers on the gauge. When you reach the proper reading, release the pressure.
You now know the basic use of a torque wrench. You are now a more attentive mechanic (shade tree or otherwise). The proper use of the wrench potentially saves you from headaches down the road. Especially if you tend to overtighten nuts and bolts, like I used to.
