The Optimal Speed
If the RPM of the machine is too low, the cut-off wheel and grinding disc tend to “jump”, and the disc edges wear down unevenly. Particularly with thin material cross-sections, such as cutting in or wire, this causes the grit to be separated from the bond and the disc wear speed is above average.
Polymak cut-off wheels and grinding discs are high-performance products and were developed such that best disc performance (measured according to the stock removal volume to disc wear ratio) is achieved in the range right below the maximum peripheral speed. Keep the machine running at a consistently high RPM and, if needed, select a more powerful machine.
The maximum RPM and peripheral speed are printed on the label of each disc. For your own safety, please be sure not to exceed the recommended speeds when grinding.
The Correct Grinding Pressure
An important requirement for a satisfactory cutting result is the correct grinding pressure. A common mistake is to reduce the grinding pressure to preserve the disc and extend the cutting life of the wheel. If this is done, the material overheats (turns blue); the cut-off wheel becomes clogged and “burns up”. This is why the grinding pressure should always be set such that the cutting time is as short as possible. This is particularly true for heat sensitive material with large material cross-sections
The Proper Hardness
For cut-off wheels
Generally, the rule of thumb when selecting the correct cut-off wheel is: the harder the material, the sifter the abrasive bond.
The reason: the service life of a cut-off wheel is dependent on whether the cutting surface of the workpiece hardens or not. Overheating results in the disc “glazing” and the cutting properties are negatively affected. In this case, the hardness of the bond should be decreased and a softer cutting-off wheel should be used.
For grinding discs
The rule of thumb also applies to grind discs: the harder the material, the softer the grinding disc bond. In addition, the application plays a decisive role. Corner grinding and the grinding of burrs and sharp edges can cause grit to be removed from the bond. We suggest the selection of a hard bond. On the other hand, when working on surfaces or small weld seams a disc that is too hard would become dull and would no longer be effective. It would have a good service life, but would also have a low stock removal rate and high work costs. A medium or soft disc bond would be best for finish grinding.