After you've tightened your fastener, use a torque audit wrench to slowly apply force in the tightening direction until you notice the first movement in the fastener. The reading is a reliable indication of the originally-applied torque. This is the most trusted measure of torque after tightening.
Movement Method
Once the bolt is tightened, the bolt and workpiece/product are marked off with a torque measuring tool. Then, additional force is applied in the direction of tightening until bolt movement is seen. The torque reading at that moment is the residual torque initially applied to the bolted joint.
Torque/Tension Rules of Thumb
35% overcomes thread friction. 55% overcomes under head friction. 10% created clamp or tension.
Right Hand Rule for Torque
To use the right hand rule in torque problems, take your right hand and point it in the direction of the position vector (r or d), then turn your fingers in the direction of the force and your thumb will point toward the direction of the torque.
However, if the tension is too low, the nut could vibrate or work loose. If the tension is too high (overstretched), the bolt could break. Every bolt has a correct optimum torque/tension figure for each fastening application.
Check the Turning Direction
Hold the socket in one hand and use your other hand to move the ratchet handle left and right. It will only move in one direction. To loosen a nut or bolt, the socket handle should turn counterclockwise. To tighten a nut or bolt, the socket should turn clockwise.
Mark the tightened fastener and surrounding application. In the tightening direction, begin to slowly apply force to the tool until the first movement in the fastener is noted. The reading recorded is a good indication of the original torque applied to the joint. This is the best way to determine residual torque.
If you know the motor efficiency and the shaft speed, you can use a power meter to make an estimation of torque. This is an indirect way of measuring torque. A better and more accurate way to measure torque is using a direct method, using reaction torque sensors or rotary torque sensors.
Verify Torque is a smart device that revolutionises torque traceability. It is a Bluetooth® torque wrench adapter that attaches to your existing tools, digitally capturing your torque data via a dedicated reporting app for compliance and traceability, that is securely stored in the cloud.
Hand Tightening and Feel
This technique involves using your hands and a wrench to tighten the bolt until it feels snug. Then, use an additional quarter turn (90 degrees) to achieve the appropriate torque. This method requires experience and practice to avoid over-tightening.
After tightening the bolt, mark the bolt surface and that of the product or workpiece. Then loosen the bolt. Re-tighten it until the markings re-align. The torque needed to return the bolt to its original position is the torque value of the bolt.
Ruining the Fastener
If the screw is so tight that the tools mentioned above cannot move it, applying them may cause the screw head to strip out or snap off, which compromises the integrity of the attachment and renders the fastener useless.
Find the torque measurements printed on the wrench's main shaft, just above the handle. These measurements are typically in increments of 10 or 20 pound-force-feet (lb·ft) or newton-meters (N·m). The vertical marks on the top dial of the handle increase by 1 lb·ft or 0.14 N·m increments.
The wrench has a clutch mechanism that makes a clicking noise and slips when the maximum level is reached to prevent exceeding the preset torque level.
What are the risks not using a torque wrench? Too loose: Have you ever paid attention to all those wheels you can see by the roadside? If you don't bring enough torque when tightening a bolt, there is a risk for the bolt or nut to spontaneously unscrew down the road.
Loosen the bolt using a torque wrench and read the torque when the bolt starts moving. Tighten the bolt further to determine the applied torque. Read the torque when the bolt starts moving again. Mark the position of the tightened bolt, loosen it and read the torque when retightening it up to the marked position.