ATM Greetings

[Aplanatic@aol.com]

Dear Fellow Grinders,

I've briefly rejoined this list to thank you for recent emails regarding my broken web pages.  I've received a number of emails from ATM list members with suggestions and offers of help, etc.  Thanks!

After being alerted that the web pages no longer exist, I've assessed the damage and have contacted my ISP.  It appears that quite a lot of stuff is gone and my ISP doesn't have a remedy (or much of a clue, in MHO).  I am not really interested in trying to reconstruct the material, but if someone would like to upload old/saved information to anywhere they see fit, well, that's fine with me, and I'd appreciate it.  Thanks in advance.

Other news:  Our little group of telescope makers finally received the big cellular blank that we've been waiting for (three and a half years).  As you may recall, we're building a 42"-aperture corrected DK broken-focus Cassegrain.  The blank is about 6.5" thick and weighs 285 pounds.  It was spun cast to our final radius of curvature (well, almost, but that's another story).  

We had to grind down the first 2.5 mm with 60-grit to remove a layer of bubbles and surface oxidation.  If you're wondering, it took about 50 man-hours to accomplish this, mostly with two people grinding simultaneously using 18" tools.  Yes, there's more than enough room on the blank for two tools.  It's kinda like synchronized swimming.  :>)

We're on 120 grit now, and have about 25 man-hours of grinding with it.  The 60-grit monster SiC particles leave huge subsurface fractures that take a long time to remove.  I expect that another 20 hours will be needed to get rid of the pits.  After that it should be smooth sailing down the grit scale and on to polishing.

If you're interested I'll drum up some pictures of the blank and upload them to a web site (ha ha).  Presumably, they'll stay up long enough for you to take a look.

Happy grinding,
Dave Rowe