RE: [ATM] Figuring nightmare I need your help

["Darran Summerfield" <darran.summerfield@ntlworld.com>]

Brent, 

I'm relatively new to this but my recent experiences might offer
something. I've been trying to get my 10 inch mirror to a sphere using a
full sized lap (it was too flat with a turned edge). I was having little
success with getting the figure to budge, after many hours of trying I'd
achieved very little, until I tried heavy pressure. With the tool on top
and a 12 lb weight an hour or so of polishing has significantly moved
the figure in the direction I wanted it to go. However, it has
introduced some roughness that I'll have to smooth out.

Darran
Boston Spa, West Yorkshire, UK


-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf
Of Brent Russell
Sent: 01 October 2004 16:40
To: atm@atmlist.net
Subject: [ATM] Figuring nightmare I need your help

Hi folks,
I received no replies to my last message posted to the list. So I try
again
I am trying to figure a 12.5" plate glass mirror. Figure is mooth and
edge is good. I am using a 10" a 6" and a 3" tool.
The mirror is about 2.5 to 3 waves over corrected and I cannot no matter
how hard I try get the edge zones to flatten out. I am desperate here. I
am nearly at the point of re fine grinding. No matter what I do the edge
zones will just not respond to anything I do
I have tried 25 times round with the 3" on the high spot no change I
have tried chordal strokes with 6" tool just inside the high spot no
change I have tried 20 minutes with the 10" tool using a chordal stroke
with about 1.5" overhang - no change to the edge zone
HELP PLEASE :-0
Do I make a full sized lap
Do I re fine grind
Do I try different strokes

Regards,
Brent

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