On 03/05/2011 08:28 AM, james122964 wrote:
> Glad I asked about the I beam, seems everyone experience counters my intuition because I thaught I beams were very ridged and strong. I have some square 2 inch 250 wall maybe I will try and fit that in instead.
>
> To all, I realize that I do not know what I am doing, I just have the basic skills to accomplish it. I have been making things from metal for quite some time and casting repair parts, although not on the scale needed for these machines.
>
> I really appreciate the advice and frankness.
>
> thanks
> Jim
Just as a point to ponder, consider the tube with no fill to damp
vibrations. Tap it with a hammer and see if it rings, if it does, the
finish on workpieces will be affected. Consider filling it with clean,
dry sand and tapping again, it will probably go "thunk." Better fills
(like pure lead and composites) will make it more rigid, but regular
concrete is bad, it shrinks. There are non-shrinking grouts (like
concrete, but a different formulation) which should be better, but the
corrosion of the steel is a matter of concern.
Personally, I like epoxy/granites (E/G), but they are expensive. Be
sure that ALL holes are drilled and tapped BEFORE filling the tube, and
that plugs are in place. Machinable wax plugs machines as screws are a
good idea here, either they come out, you drill them out, or you can
melt them out, but drilling and tapping composites (like E/G) is not
trivial. RIVNUT® closed end fasteners
<http://www2.boellhoff.com/web/usa/en/web.nsf/HTML/index_us.html> are
also a good choice, they do not allow the fill to leak and provide good
threaded holes.
Dave 8{)
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