Re: [ATM] draper

["Bob May" <rmay@nethere.com>]

Don't ovrfthink what is going on!
The thing here is that where the tool is grinding is where the
glass is eaten away.  The smaller tool is the one to use for
hogging as this will produce the highest forces for the weight on
the tool. Make the tool cross in the center and start with just
going near the edge and get the center down a little bit.  After
you get to about 30 percent of the depth, lengthen the stroke and
go over the edge by a little bit to even out the whole surface.
You will quickly find that lovely point where you make a
spherical surfcace with the hogging toool and you can then go
from there.  Once you have finished the hogging, you can then do
a full sized tool and go down therrough the grits.  Remember that
whatever is on top will tend to become concabe so you will want
to go to the ROC desired in hogging and watch the ROC as you go
down through the grits.  It will probably lenghen a bit so be
prepared.
A machine, of any type, is nothing more than a labor saving
device to get rid of having to push the mirror and tool all oer
the place.  Use it accordingly and things will be alright!
I'll also note that for rough grining, spin that thing up and
watch the glass go away.  You can't hurt the glass at that point.
The only time that you really need to go slow is for figuring and
polishing with pitch as the pitch will warm up and cause all
kinds of interesting things to happen.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net


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