When polishing by the polishing machine, the grinding surface of the sample and the polishing disk should be parallel and evenly lightly pressed on the polishing disk, and care should be taken to prevent the sample from flying out and generating new grinding marks due to excessive pressure.

At the same time, the sample should also rotate and move back and forth along the radius direction of the turntable to avoid local abrasion of the polishing fabric too fast. In the polishing process, the micro powder suspension should be added continuously to keep the polishing fabric in a certain humidity.

If the humidity is too high, it will weaken the grinding mark effect of polishing, which will make the hard phase in the sample appear convex, nonmetallic inclusions in steel and graphite phase in cast iron produce "tailing" phenomenon. When the humidity is too low, the friction heat will increase the temperature of the sample, reduce the lubrication effect, make the grinding surface lose its luster, and even appear black spots, and light alloy will damage the surface.

Of course, in order to achieve the purpose of rough polishing, we require the rotating speed of the turntable to be low, not exceeding 600 r/min; The polishing time should be longer than the time required to remove scratches, because the deformed layer should also be removed. After rough polishing, the grinding surface is smooth, but dull, and there are uniform and meticulous grinding marks observed under the microscope, which need to be eliminated by fine polishing.