How to Operate a Torque Wrench

One of the must-have tools for the do-it-yourself auto mechanic is a torque wrench. A torque wrench is similar in appearance to a normal socket wrench except that is has a dial mechanism used to adjust the amount of force, or torque, delivered to the nut or bolt. A torque wrench is used to accurately tighten a nut or bolt that requires a specific amount of torque. It is easy to torque a variety of nuts and bolts to an exact degree of tightness by following a few simple torque wrench operating procedures.

Things You'll Need

• Safety goggles
• Clean rag

Instructions

1. Determine the specific amount of torque required to fasten a nut or bolt, based on the manufacturer's specifications. If you are unsure, check the manual for the vehicle or the device you are working on to find the recommended torque value or range of values.

2. Put on eye protection. Clean the threads of the bolt or assembly that will be tightened, and check to make sure they are in good condition. Dirty or damaged threads will give false torque readings.

3. Select the desired socket (SAE or metric) and make sure that it is the correct size socket for the type and style of bolt being tightened. Press the socket firmly onto the drive anvil of the torque wrench. This is the square-shaped protrusion sticking out of the head of the torque wrench at a 90-degree angle.

4. Adjust your torque wrench by turning the knurled metal handle grip located at the base of the torque wrench handle until the "0" graduation mark imprinted on the base of the handle aligns with the bevel edge marked "50" located on the shaft of the torque wrench. By twisting the handle until the "0" mark on the base aligns with the "50" mark on the shaft, you have set the torque wrench to signal when 50 pounds of torque has been attained.

5. Make further adjustments to the torque wrench in this manner (either more or less torque desired) until it is set to the desired force for the bolt you are tightening. Once the torque value is set, tighten the lock knob located next to the knurled metal handle grip so that it cannot move accidentally.

6. Set the wrench direction ratchet switch for clockwise or counterclockwise operation. The switch is visible and located beneath the head of the torque wrench. Pressing the switch to the left allows for counterclockwise torque to be delivered; to the right delivers clockwise torque.

7. Attach the socket wrench combination to the socket, making sure it fits snugly. Tighten the wrench slowly by pulling the handle of the wench in the clockwise direction. Continue to pull the handle gradually until you hear the wrench click or you feel it. Do not pull beyond that point or you will be applying excessive torque. The click indicates that the torque setting has been attained.

8. Remove the socket and torque wrench from the bolt. You are now free to torque a new bolt to the same specifications, or adjust the torque wrench to a new setting. Wipe the tool down with a soft clean rag when you are finished before storing it.

Tips & Warnings

• Torque values for smaller bolts are measured in "inch-pounds"; for example, 20-200 inch-pounds. Larger heavy-duty applications are measured in "foot-pounds"; for example, 5-80 foot-pounds. Some wrenches use metric settings, some use U.S Imperial settings. Be sure your wrench is set according to the units recommended for the bolt or the assembly you are working on.

• Bolts can snap when a high amount of torque is applied and can be dangerous. Always wear goggles to protect your eyes in the event of a snapped bolt. Tighten bolts slowly. Torque wrenches are not designed to measure rapid forces, so slow, steady pressure must be used. Going slow also allows you to hear and feel the wrench click once the specified torque has been reached.

References

• Harbor Freight Tools: Pittsburgh Torque Wrench Assembly and Operating Instructions

Resources

• Read this Article in Spanish