From: "Frank Ward" 
To: "Jean-Guy Moreau" 
Cc: 
Reply-To: "Frank Ward" 


Jean-Guy, You asked...

>how you reduce a high edge zone, and/or lack
of polish on edge with your machine ?<

I've seen your posts on the list for years, sir, but I don't remember your
level of experience. Forgive me if I go to basics. I don't mean to insult,
but there are others who might get benefit from a "general"
response.

You express two challenges. First reducing a high edge zone and secondly a
lack of polish on the edge.

They don't go together. Only when your surface is totally polished out is
it ready to figure. The series as I try to follow it is:
hogging,grinding,smoothing,polishing,figuring, testing,coating,viewing.

However, if you want my method for reducing a high edge zone... I assume
you mean a hyperbolic surface where the last Foucault tests show higher
numbers than you want (which describes this surface). I put the work
surface on the rotating disk (25 rpm) and after preparing the tool, place
it on top. I hold the tool in my hands, not attached to the overarm, and
make my strokes thru the center of the work surface without a lot of
overhang. The pressure from my fingers attempts to "lift" the
tool as it returns over the edge again to avoid turning it and pushes down
when it is "going up the hill". Every six or eight strokes I go
out to the sides a little to keep the surface blended. When I do this I am
using the normal parabolizing stroke but in reverse. That will lower all
the numbers so I am very careful to use it sparingly.

But Do you know the numbers you want? For me that is the important thing. I
use Fig45 for that phase of my work. It takes awhile to flip between F3 and
F4 but I can get a hypothetical surface of 150th wave RMS. Those are the
numbers I work toward. In that way I always know what part of the surface
needs work. Sometimes I'll leave an area of the surface that is perfect
just for the privilege of getting all the numbers lined up .010 off. That
way I can finish with a full sized lap which gives a smoother finish
without the roughness or lines that a small tool can cause when we work on
just one area. Keep smiling. Figuring a mirror is like having sex. When it
stops being exciting we need to stop doing it.

Best wishes,

Frank Ward
Atlanta,GA

-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of
Jean-Guy Moreau
Sent: Thursday, August 21, 2003 8:23 AM To: Frank Ward; Jerry B. Hillman
Cc: ATM{at}Shore.net
Subject: Re: ATM figuring question



Frank, how you reduce a high edge zone, and/or lack of polish on edge with
your machine ?

size and shape of lap, kind of stroke, length ?

Thanks,

Jean-Guy

> If your outer three zones are going up, then flip the mirror
> on its back and after a long cold press use the tool on top.
> Then do back and forth strokes across the center with only an
> inch or two overhang at the end of each stroke. I
> use a machine so it's hard to translate, but what you want is
> to keep the tool in contact with the edge, you do that by allowing
> very little overhang. The more the overhang the more time the
> tool is not in contact at the edge. With the heel of your hand
> pressing down try to "push glass up the hill" and over the edge
> as I like to think of it.
>
> That action will lower the edge numbers, hopeful without lowering
> the middle and 707% zone too much too.
>

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