Pit Sizes

Bob Luffel (bobl@gr.hp.com)
Wed, 8 Mar 95 13:13:06 MST

I am grinding a 10" f/6.3 mirror out of russian Sitall - I finished up (I hope) with 20 micron last night. There still remain numerous randomly distributed pits of approximately 25 microns in diameter that refuse to disappear. I presume that these are being caused by the 20 micron grit(or, rather,perhaps some larger grains included in the 20 micron). Can anyone tell me if pits of this size are normal at this point? I don't want to proceed to the next grit, otherwise. I seem to remember a past post to this group that listed the expected pit sizes for different grits (for aluminum oxide, I seem to recall a value of slightly larger than the grit size).

Bob