Re: [ATM] keep polishing or return to fine grinding?

["Mel Bartels" <mbartels@bbastrodesigns.com>]

> I'm working on my first mirror, an 8" f/6. I'm having trouble getting the
> edge to polish out, or for that matter, to polish at all (after 6 hrs). 
> The
> rest of the mirror looks great. I performed several warm and cold presses,
> but they do not seem to help. The region in question is the last 0.5".
>
> Second, I'm convinced that my lap was too hard (Gugolz #73) for working
> indoors ( 72-75 F) as it constantly slipped and grabbed no matter how many
> cold presses I did. I just ordered some Gugolz #64 to try out. I am hoping
> this was a good call.
>
> Third, should I return to 18 or 9 micron AlOx to ensure I have a good 
> shape?
> I did this once before to remove several scratches, but maybe I ruined the
> shape?


We can really only guess as we cannot look over your shoulder.  Most likely 
you are fine, and simply need to get good contact with the lap.  Less hard 
pitch would definitely help.  Even the #64 might be a tad too hard for you. 
Warm press by floating the lap in fairly warm water, then pressing against 
mirror, then dunk lap in cold water to 'freeze' the shape.  Do longish 
strokes with tool on top.  Press hard.  Optimally, one can polish out an 8 
inch in a couple of hours, so you should be able to catch your edge soon. 
If you do see lots of heavy pits near the edge, then you might have a fine 
grinding problem, but that's not the most likely situation.  You might try 
to find someone to look over your shoulder.

Mel Bartels 

_______________________________________________
ATM mailing list http://www.atmlist.net/