When a crack runs through a peg hole, the best way to repair that is to first line up the crack and glue it. Then fit a spiral bushing for the hole. Glue the bushing in then trim off the excess bushing. Using masking tape on the outside cheeks of the peg box speeds up the process and protects the scroll. Once you have it trimmed to the thickness of the masking tape, the final adjustment is fairly easy. This was a viola where the pegs were originally lined up incorrectly. The "D" and the "G" strings rubbed on the other pegs. To correct this problem, the "A" peg was moved down 2mm and the "D" peg was moved up 2mm. First the boxwood bushings were fitted, then the outside faces were carefully made flush with the peg box. Then the new holes were drilled and the pegs were fitted. Then there was a slight amount of varnish touch up to make the boxwood a matching color to the original varnish.
Here is a violin that had a very old style friction peg, plus it had previously had geared pegs installed. The holes needed to be bushed with a spiral bushing and then some new pegs installed. A customer brought in a cello where the "D" peg was solidly glued together. It would not turn. I managed to get it out of the peg box. Since she wanted the pegs to match, I looked around and found that same style old peg. They are a mixture of metal and plastic with a bushing that's similar to the Caspari style. I installed the used page but about a week later it started to fail. I took it apart and realized that the plastic part of the peg was slipping aghenst the metal part of the peg. There are fine slots on the metal and plastic that when engagued don't slip. In this case the plastic slots were stripped out. I took the peg apart and carefully glued it back together. Here are a couple of photos. . | 
