[ATM] Help with stubborn zone on 12.5"

["Brent Russell" <brussel@bpc.org.za>]

Hi all
 
It has been some time since I was part of the list and it is good to be
back. I am currently building a 12.5 inch scope and am getting very
frustrated with my mirror. I have never had a zone quite this stubborn
before.
 
I am using a 10" channelled pitch lap as well as a 6" channelled lap to
figure. I have feathered the channels on the 6" so that it reduces the
edge of the tool reducing zones.
 
So here is my problem. The mirror is a 2.5 wave hyperbola ie
overcorrected. I can control the depth and shape of the centre
wonderfully with the 6" tool without any zones. But reducing the depth
of the edge is a MAJOR problem.
 
I have tried chordal strokes with the 10" tool and these helped somewhat
as the standard W strokes is well known to produce an overcorrected edge
with a smaller too. I have tried using the 6" tool on the top of the
edge zone (about 85% radius) and this has helped a bit but not enough.
Even after 3 lots of 4 rotations of the 6" tool the edge has only budged
a little....any ideas?
 
Do I try a small 3" tool? Other strokes any ideas would be great.
 
Thanks,
 
Brent
 
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