On Monday, March 16, 2015 at 1:12:58 PM UTC-4, Spehro Pefhany wrote:
Wow. And his other videos, too. Wow.
About thirty years ago I worked on the controls for a machine (a giant, hyp
er-precision photo plotter) that had a 6' x 8' slab of granite finished to
millionths, that moved on air bearings. Very expensive, very cool stuff. I
had forgotten about granite as a relatively inexpensive precision building
You... um... don't own a surface plate; right? <G>
Yeah... Granite has been around for quite a while as a "precision
surface". Even your corner gravestone grinder can face a slab off to
within a thou.
The only guy I knew in college who retired with a turbo-prop, paid-off
home, no bills, and a good pension by the time he was 40 was a maker of
blank gravestones. He did surface plates as a "fun sideline". The real
money was in tomb markers. He used to brag that his grinder could do an
8' x 12' plate to within a tenth corner-to-corner. He said that was no
trick, at all. The real trick was getting it on and off the bed!
(and yes, he had the whole volume of space around and in the grinding
zone temperature-controlled). Even the water was pre-heated or cooled to
EXACTLY the stable resting temperature of the work. He had it nailed!
On Tuesday, March 17, 2015 at 6:30:10 PM UTC-4, Lloyd E. Sponenburgh wrote:
Yes, I do own a surface plate. I was talking about actually building stuff (other than buildings and gravestones) out of granite.
As I recall it, the people making the large slab could only work on it a couple of hours a day towards the end of the process, as the friction from grinding would heat it up too much.
Good thing that gravestone guy is already retired. I hear that the gravestone business is dying. (sorry).
On Tue, 17 Mar 2015 19:38:08 -0500, the renowned "Lloyd E.
Sponenburgh" <lloydspinsidemindspring.com> wrote:
In one particular venture (past present or future, something like
that), I'm holding out hope to live on as a small part of a Harvard
Business School case study of what not to do in a tech start-up.
"it's the network..." "The Journey is the reward"
firstname.lastname@example.org Info for manufacturers: http://www.trexon.com
On Mon, 16 Mar 2015 13:15:39 -0400, Spehro Pefhany
Wow, that's very cool. It reminds me of another air-bearing,
granite-based lathe made in the '80s, from Pneumo Precision (now part
of Corning). It was built for diamond-turning optics.
BTW, I can't see what linear motors would do for it. I see that Dan
Gelbart has a bunch of interesting videos there. He appears to be one
heck of a craftsman.
Also BTW, those dynamic air bearings were used on internal toolpost
grinders back around 1910 - 1920. That's an interesting story in
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