Electronic angle control wrench for turn-of-nut tightening
Currently Torque Method is widely adopted for tightening high-tensile bolts. This is the method to induce targeted tension into the bolt based on the principle that the torque added to the nut is almost directly proportional to the tension induced via the parameter of torque coefficient, K-value.
Torque Method is one of the most dependable methods for tightening nut, however, this method can not be escaped from following points;
- Torque coefficient (K-value) is variable depending on surface treatment & aging condition of bolts/nut/washer, dust and temperature.
- Tightening equipment needs to be calibrated before operation.
- After tightening inspection is necessary by manual torque wrenches to confirm tightened torque.
On the other hand, Turn-of-Nut Method is capable to solve such drawbacks associated with Torque Method and is one of the excellent alternative tightening methods widely selected in advanced countries.
The Principle of Turn-of-Nut Method
Turn-of-Nut Method is based in the thought that the amount of tension induced in the bolt can be presumed by the degree of elongation of the bolt. The diagram shows the general relation between the bolt tension and the nut rotation angle when the high tensile bolt is tightened. At the initial stage, the diagram is curving due to loose fit of connection materials and etc, however, in the later stage shows a liner relation within the elastic range. As nut rotation is proceeded, the bolt goes into plastic range. At this stage, the increase of nut rotation angle quantum does not affect the increase of the bolt tension.
Benefit of using Turn-of-Nut Method is Simple Operation!!
1 . Required tension can be induced by giving determined rotation angle to the nut.
2. Since there is no influence on vulnerable torque coefficient (K-value), strict torque control is not necessary.
3. Tightened torque inspection by manual torque wrenches can be deleted.
4. Due to high tension induced, fatigue life of connections or slip resistance can be dramatically improved.