[ATM] Question on my lap for 8" F6

[Scotto1234 at aol.com (Scotto1234@aol.com)]

I have been trying to figure an 8" F6, and I am having nothing but trouble.  
I have an oblate spheroid, and no matter what I do, it only gets progressively 
worse.  I have been contemplating what might be the cause of it.  The only 
thing I can think of is that I made a tile tool to grind, and therefore had a 
flat blank instead of a spherical one to make my lap from.  What this means is 
the facets in the center of the lap are thicker than the ones at the edge.  
Will this cause the ones at the outer edge to be more rigid and thus push the 
mirror more towards an oblate?  Has anyone used a flat blank for their lap with 
success?  I don't know what else it could be.  I even worked MOT and did the 
stroke for hogging out the center of the mirror when grinding (center of the 
mirror at the edge of the lap with short tangent strokes) I would have expected 
this to deepen the center.  I did it for 15 minutes and it just made the oblate 
shape more extreme.