Re: ATM Alternative grinding machine (Simplier?)

[mjc5@psu.edu]

	I suppose I shouldn't bring up my idea for grinding by 
suspending a well drilling truck on chains over the mirror 
blank........ 8^)

	But seriously, give a try of actually making a mirror by hand 
before going off on tangents about making what amounts to a 
"one-step" machine.

	The precision of even a poor mirror is amazing when considered.

	When I parabolize a mirror, I use only a couple trips around 
the mirror with the tool using thick slushy polishing compound to cut 
the polishing action down.

	Trying to achieve this surface in the grinding stage is 
simply not possible, because the grits are just too big, as Ken 
points out.

	To suggest otherwise exposes ignorance of the fundamentals. 
This is not a fault, mind you. EVERYONE here was equally ignorant at 
one point.

	So slow down a minute, lissen up and we'll have you making a 
nice mirror soon. You sound inquisitive and experimental, and those 
are good qualities in an ATMer. Hang in there!

Hope this helps

	- mike -

>Yes,
>
>The abrasive size at grinding is a million times larger than the 
>total correction of the parabola. The grit size deviation is usually 
>+/- 25% of the nominal grit size or roughly 200,000 times the 
>parabolic correction.
>
>We already use very fine diamond tools to generate a spherical 
>surface and are lucky if it's close enough to use #320 grit to get 
>to a real sphere... so there is no way you could generate a parabola 
>with rough grinding grit.
>
>Not even close to a good idea. Why don't you go through the process 
>once to make a mirror before coming up with a thousand ideas to 
>modify something you do not understand?
>
>Sorry to be so negative but you are wasting a lot of our time with 
>all these hair brained ideas.
>
>Ken Hunter

--