Re: ATM chasing spheres $%$^&*(%^&$%^!!!!!

[Cary Chleborad <bennu@ns.net>]

Tom Krajci wrote:

> How long are you grinding before you look at the graphite pattern to
> determine you've got this raised ring?  The reason I ask this is
> because I used to test how well the tool and blank are in contact
> during rougher grits (although I did it by rubbing them together when
> dry. . .you see a different color/pattern where contact is being
> made)  And this is what I found:  I never got 100% full contact
> between tool and blank at 80, 120, and 220 grit (I stopped testing at
> that point).
> 
I must have chased my tail around in circle for about 5 hours on 120
grit.

> Did that matter?  No.  So far I've polished out 13 mirrors I
> ground with a machine - not a single problem due to bad tool/mirror
> contact.  (And I was making these mirrors in sets of four with a
> single aluminum tool. . .there's gotta be more tool/mirror
> contact problems built in with this approach and I still had no
> problems.  I'm currently grinding a set of five mirrors against one
> aluminum tool and I bet I won't have any contact problems.)

O.K. I've taken your advice and not worried about it.  I've already
ground down to 600 grit and I should be able to polish out the mirror
tomorrow (saturday). We'll seen how things go!

Also, this is a two time first for me....#1 it's the first time I've
ground a mirror on a machine and #2 it's the first time thatI've used an
aluminum tool.  I can't believe how fast you can grind out a grit size
compared to working a mirror by hand.  My qustion is, is it the machine
action or the aluminum tool, or both that make it grind so dang fast?

> 
> Also, how much weight are you using on the pin?  I use up to 30 lbs
> for the silicon carbite grits to speed grinding and I've had no
> problems. . .only an amazingly short grinding time.

Since the arm is manually controlled, I manually apply pressure during
the roughing out stages, maybe up to 50 pounds or more( I lean on the
lever arm), then I switched to 5 pounds at 120 and 220 and from then on,
just the weight of the tool and arm.
> 
> Hope this helps,
> Tom Krajci


thanks for your help...

-Cary Chleborad