ATM 1st mirror - machine use

["Tom Krajci" <krajcit@det5wg57.barksdale.af.mil>]

Thanks for all the advice so far!  I have another question.

I'm done with 320 grit on my 6 inch, f/3.67 and will proceed to finer 
grades.  I'm using a grinding machine and have 20 lbs on the arm 
to speed grinding.  As I go to finer grits should I:

1.  Reduce the weight, and to what value?

2.  Are stroke size/shapes different for machine work versus hand 
work?  (I'm using TOT, 1/4 strokes in a "W" that provides about 3/4" 
overhang at each side of the "W.")

3.  Go to hand work at a certain fine grit?

4.  Could I even polish by machine?  Maybe for the first few hours?

Thanks in advance!

PS.  As a follow up to my postings on "Mirror and tool mating 
patterns" the mating pattern has really improved as I finished 220 
and moved through 320.  The zone of contact grew from a relatively 
small zone and appears to encompass the entire surface!  It is harder 
now to see the mating area with the finer surface finish - perhaps 
this trick only works on the coarser grits.  I'll stop using the 
technique since I'm afraid of scratching, but it was interesting 
seeing this change take place.  I'll interpret it as an indication of 
good progress.  The permanent marker test, coupled with tracking 
progress of the biggest pits that I "tagged" with china marker on the 
mirror's back side gives me confidence that I'm done with each grit 
size.

Tom Krajci
B-52 Intelligence Officer
http://spur.barksdale.af.mil