Defects of the tool do not hurt the mirror. So bevel the tool around the chipped area only to prevent further chips of glass from coming off. -- Clear skies, Mel Bartels Programmer/Analyst, amateur astronomer Eugene, Oregon, USA homepage: http://www.efn.org/~mbartels mailto:mbartels@efn.org atm, atm-digest list-owner Motorize A Dob: http://zebu.uoregon.edu/~mbartels/altaz/altaz.html