Because each person uses a different turntable and grinder when using a polishing machine.
Use a thicker polishing disc such as a wool disc, and it is easy to wear through the polished piece by increasing the rotational speed, so the rotational speed is generally set at 800 to 1200/min. Similarly, if a coarser abrasive is used, the RPM will need to be turned down a bit.
In some cases, in order to improve the polishing quality, it needs to be carried out in steps, rough polishing and fine polishing, and the rotation speed of these two stages is different.
Rough polishing requires a lower rotation speed of the turntable, preferably not more than 600r/min; the polishing time should be longer than the time required to remove the scratches, because the deformation layer is also removed. After rough polishing, the grinding surface is smooth but dull, and there are even and fine wear marks observed under the microscope, which need to be eliminated by fine polishing.
During fine polishing, the speed of the turntable can be appropriately increased, and the polishing time is appropriate to discard the damaged layer of rough polishing.