From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 


Mark the disk with a magic marker or sharpie pen and do a few strokes all
over.  How's it wearing?  Also, watch air bubbles.  they get broader and
larger when they get to a zone that has less space. Typically an air bubble
will get smaller when it hits the too deep center.

The "edge strokes late in the game" are not a definite cause of
lowering the edge out of spherical.  It should bring you closer to a
sphere. Maybe shorten them a bit.

Try a wet of 400 grit or so and see where it grinds, using the slanted
light technique.  the areas out of contact will reflect far less light.

I'd guess you're ready to move on, but try a few tests to learn what's going on.

Colin



-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of J
Killea
Sent: Wednesday, April 30, 2003 10:33 PM To: atm{at}shore.net
Subject: ATM Rough ground to edge; not a sphere, what next?



I have been rough grinding an 8" blank, have a target sagitta of
.083" (f/6), yes I'm a newbie.  I
was too deep (.089") upon reaching 1/8" from the edge so I ground
to the edge using TOT cord
strokes with about 30% tool overhang and outside pressure.  So, I have
reached the edge (sag. is
now ~.082"), but due to edge strokes late in the game I have no doubt
this is not a sphere.
Probably a deep center and much longer ROC near the edge.

I would rather get more spherical with my 80-grit before going to 120,
since it should go faster
that way.  I'm leaning toward long normal strokes with whatever combo of
TOT and MOT necessary to
maintain my ROC.  However, I would appreciate any suggestions on both
stroke type and grit.

Thanks very much!

-Jay

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