Re: ATM bulls eye on faucault test

["Bob May" <bobmay@nethere.com>]

                                    DON'T WORRY! ! !
                                            All is fine!
Believe it or not, that is a normal appearing surface and the only thing
that you have to be sure of is that the edge isn't turning down with a much
longer radius than the other zones.
What is happening is that the pads aren't smoothly curved on the tool like a
pitch lap is so you will be getting all kinds of zones.  If you want to cut
them back, change the length of your stroke and they will blend together.
The usage of the pads is to get the surface quickly polished out and pitch
should be used to smooth (usually about 15 min.) and then figure the mirror.
You are probably using a very regular stroke to get so many zones so you
might want to change the stroke length so that they blend.  Please note that
the stroke can be of a fairly long length as the pads aren't going to move
hardly at all but don't go too far or you can indeed get the center to a
different radius than the outside as you did when rough grinding.  You can
also change from MOT to TOT without the large change in FL that comes with
it on pitch.  The pads are rigid in their position and this is the problem
that is causing the rings.  Don't bother to try to bang down offending areas
as that will just cause frustration at the failure.  It's the way pads work.
Bob May
http://nav.to/bobmay
bobmay@nethere.com