I’m polishing a synthetic spinel and the table is starting to show pits. At first everything seemed to go well with my BA5T lap with 100k diamond and then the facet edges started to show chips. I moved to the Darkside and stayed using aluminum oxide and got the chipped edges removed. Then I started to see small pits which I slowly tried to work out. Then I got a groove (not scratch) which I am now trying to work out.
What else can I do? I’m working on a competition stone and would like sharp meetpoints. Should I use another lap? What else can I try/do?
What you may be seeing is the dreaded orange peel which spinel happens to be prone for that. For one thing I never use a 1200 lap on this stuff but rather go directly from my 600 sintered to something higher like 3000. For some reason that seems to avoid the problem. If you do encounter orange peel you have to back up in grit size. For example encountering it at 1200 you have to go to 600 and recut or waste a lot of time. Pits resulting from bubbles is unlikely in sync spinel. Keep at it. Spinel cuts beautiful stones a good seller for me.