Re: [CAD_CAM_EDM_DRO] Re: real granite machines!

My thoughts on using granite for slides are these:
1. On the top slide, you will be needing T slots or some other method for
attaching the workpieces. these slots(if used) should be accurate so as to
allow using keys and other fixturing components for accuracy in mounting the
workpieces. They should also be strong enough so as not to have to worry
about part of the keyslot breaking out due to using too much force on the
nut when tightening. The keyslots should also resist wear. I believe this
pretty much rulse out granite and aluminum (unless a good wear resistant
aluminum alloy is used).
2. The crosslide may be weak (depends on actual design) due holes (or
clearance slots) necessary in order to allow the ball screw nut to travel
back and forth thru it.
3. It will be more difficult to add all the ways, bearings and other
mounted parts and get everything set up truly square and parallel as
required to obtain an accurate machine.

Smoke

-----Original Message-----
From: Joe Vicars <jvicars@...>
To: CAD_CAM_EDM_DRO@egroups.com <CAD_CAM_EDM_DRO@egroups.com>
Date: Thursday, November 30, 2000 8:12 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: real granite machines!

>How about making a big steel box and filling it with concrete?
>
>dave engvall wrote:
>
>> Jon Elson wrote:
>>
>> > I think a granite slab would make a great slide for a machine. Bolting

and

>> > gluing several slabs together would be a lot easier than making

monolithic

>> > complex shapes.
>>
>> Granite has compressive strengths of about 19 Ksi whereas it is easy to

cast the desired shapes in concrete you will loose some

>> strength.
>> Using some of the newer techniques it is possible to get concrete with

compressive strengths in the 12 Ksi range. Embedding steel

>> in this and providing decent anchors should not be too difficult.
>> Likewise one could drill holes in granite and mount components using a

filled epoxy to set anchors and maybe come out OK.

>> The local tombstone company would seem to be a better source than the lab

grade stuff. I have seen 4' x 4' by 1' pieces for a

>> couple thou. (Boeing).
>> I find the idea of a small masonry based gantry intriguing but hate to

think of the energy necessary to accelerate the mass

>> involved.
>>
>> My thinking goes more along the line of an L shape with cast iron ways,

etc anchored in masses of concrete. Has anyone tried this?

>>
>> Dave
>>
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>
>
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