The Art of Application
4. From Setting to Tightening
Having a torque wrench is only half the battle. Knowing how to use it correctly is where the real magic happens. Here’s a step-by-step guide to torquing like a pro:
1. Prepare the Fastener: Make sure the threads on the bolt and nut are clean and lightly lubricated (unless otherwise specified). Clean threads allow for a more accurate torque reading. A tiny dab of the appropriate lubricant can reduce friction and ensure the fastener clamps properly at the specified torque. Never, ever use excessive amounts of lubricant. Some applications specifically require dry threads — check the manufacturer’s documentation before applying any lubricants.
2. Set the Torque Value: Use the adjustment mechanism on your torque wrench to set the desired torque value. Be sure to use the correct units of measurement (e.g., Nm, ft-lb, in-lb). A proper understanding of your torque wrench is the key to success.
3. Position the Wrench: Place the socket on the fastener and position the torque wrench so that you can apply a smooth, steady force. Avoid jerky movements or sudden bursts of power.
4. Apply the Torque: Slowly and steadily apply force to the wrench until you reach the set torque value. With a click-type wrench, you’ll hear a click and feel a slight release. With a beam-type wrench, watch the pointer as you apply force until it reaches the desired value on the scale. Digital torque wrenches typically provide an audible beep or visual cue when the target torque is reached.
5. Verify (If Necessary): For critical applications, it’s a good idea to verify the torque with a second pass. However, be careful not to over-tighten the fastener. On the second pass, the torque wrench should click as soon as pressure is applied. If additional tightening is required, something is likely wrong. Stop and re-evaluate the situation and the fasteners.
6. Recalibrate: Torque wrenches aren’t designed for loosening bolts or nuts. They should be recalibrated every year or after a specific number of uses to ensure their accuracy. Take care of your tools, and they’ll take care of you!