Keep spray water during the repair to coil the glass and strengthen the diamond lapping film. The grinding should be steady and efficient, in a away of repeating with the following grinding covers 1/2 to 2/3 of the former grinding.Move the angle grinder clock-wisely will make the glass flat and avoid deforms. Do not keep grinding on one spot which will result serious deforms.Keep the grinding plate operating against the glass surface regularly. It will produce new scratches on the glass and make the job difficult if it is operating irregularly.Before you stop working, keep the grinding plate from the glass and turn it off. Grinding rules to follow: the next grinding area must cover the last grinding area completely or it will affect the polishing and produce new scratches.