Re: [ATM] Open Question Concerning Pitch Laps

[Bryan Stiles <bryan.stiles@gmail.com>]

Ok. So here's where I am with this. I'm gonna continue fine grinding
(500 grit) for a bit to get back to a good surface (I had a small
scratch). After 500 then on to 12 micron.

Then I'm gonna make a new lap (in case the old one has indeed been
crusted). Once I get the new lap made and cooled to room temperature,
I'll start polishing.

Now once I start polishing, when I get to the point where the friction
has fallen off, I'll stop, cold press (with weight) and begin again.
If I'm understanding everything you've said, I'll stop and press
everytime the friction falls off. Slow steady 1/3 COC MOT.

I'll try hard to get back to a smooth spherical shape. 

I do have one procedural question though. Let's say that I have been
polishing with good contact and the lap starts to slide more easily,
so I need to press. Would you recommend that I cover the mirror with
Cerium Oxide and press or allow the lap to dry out and press?

 Another thing I had a question about. I've read everywhere to
decenter the center facet of the lap and I've tried to do this with
the two laps I've made. My understanding is that failure to do this
will cause "zoning" of the mirror. My question is, what exactly is
zoning? Could this be a contributer to the central hole in my mirror
since my lap was getting close to violating this cardinal rule?

I'm embarrassed to ask such simple questions but I just don't know?


Thanks Again, Bryan
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