Re: [ATM] Polishing/figuring not going anywhere.

[Pete <lenses@adelphia.net>]

Hey Bob,
You tried what most and I would suggest first, open up the channels in 
the lap.
Repress it, but with pads you should have seen something change.
The only thing you didn't mention is polishing compound, take a look at 
that.
And switch lap and tool around, keep the stroke and rotation the same 
and that should move it.
Keep us posted on what finally works.
Good luck,
Pete
lenses at adelphia.net

Bob May wrote:

>Got a problem with some BK-7 glass that is getting me kind of
>tee'd off.
>The problem is that the glass isn't changing despite doing all
>different kinds of things on it.   I'm trying to match one lens
>to another and am sitting at about 35 rings and need to get down
>under 5 rings before I'm happy.  The surface is a convex surface.
>To date, I've used a small pitch tool on a MOM machine and let it
>sit at the edge.  Nothing happened at all.  Next tried a larger
>pitch tool and let that sit with a bit of overhang, not touching
>the center of the glass.  Finally I'm using a ring of fresh pads
>on a full sized tool and letting the pads work back and forth,
>leaving the center alone.  Despite 3 hours of doing this, the
>glass hasn't moved anywhere.
>Anybody got some ideas?  I'm about fresh out of them.  I had
>expected that the small lap would have shortly gotten me a worn
>down edge into the 50% zone with a ridge there.  Things didn't
>move at all!  Didn't matter whether the weight on the lap was
>light or heavy other than the heavy load on the lap eroded pitch
>off of the lap.  I'm still at the 35 ring diffeerence.
>For testing, I'm using a green light source and getting good
>rings promptly and am able to see a lot of rings without troubles
>until the rings get so close together that I can't seperate them.
>The pressing together of the centers of the two pieces of glass
>decrease the number of rings with all of the rings running into
>the center which indicates that the concave has a smaller radius
>than the convex that I'm working on.  The concave has the right
>radius for the application.
>The interesting thing is that it is really easy to see the TDE on
>the two pieces of glass.  The concave surface is going to have
>the TDE part ground down a bit so that the sharp edge of the
>glass doesn't hit the mounting point but that is something that
>will be done later.
>Bob May
>bobmay at nethere.com
>http: slash /nav.to slash bobmay
>http: slash /bobmay dot astronomy.net
>Replace the obvious words with the proper character.
>
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