Re: ATM Stroke for flatening flats

[Aplanatic@aol.com]

Frank wrote:

> I am now faced with three "flats" with the following surface profile with
>  respect to one another.
>  
>   
>         *                             *
>     *       *                     *       *
>  *              *             *               *  
>                     *   *  *  

This may seem like sacrilege to some, but I have had good 
success with a local polisher made by wrapping chamois around 
a soft sponge.  I cut the sponge to the desired size, in your case 
maybe two inches square, wrap a thoroughly washed new 
animal-skin (what is it? Deer skin?) chamois around it, load it 
with plenty of creamy CeO and use light pressure on the high 
ring(s).  I also use a pattern of strokes that blend across the 
zone(s).  I have never had problems with sleeks or scratches 
from this method, but "Caveat emptor."

I have never used this technique on flats, but it works very well 
on telescope mirrors.  The sponge/chamois polisher is very 
slow acting and therefore allows a lot of control in figuring.  It 
also has very soft "edges" and will not dig trenches as a small 
pitch lap sometimes will.  Of course, one must go very slow and 
test often when using any sub-diameter tool.

The other possibility, which you alluded to, is to press in a ring 
or circle in the center and/or edge of your lap.  If you try this, 
cold press the ring/circle into the lap for only a minute or so, 
and figure with it for only one or two minutes at a time.  It can 
cause quite drastic results.  A bit too agressive for my tastes, 
but it will quickly change the surface of your flats.

Dave Rowe.