RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum

There is a company here called Uni-strut in Wayne, Michigan that sells tel-spar tubing, tubing sized so that it telescopes. Its about as accurate as it gets for tubing. They have it with holes and without. Steel from other sources is getting like lumber in that its best to go to the supply house and pick it out. The characteristics of tubing vary from mill to mill. Of course, standard procedure with a fabricated weldment such as the brackets and framing like those that are used in a homebuilt CNC would be fabbed and then machined. Making the accuracy of the steel irrelevant. With this in mind, I think mills have dropped their standards to save costs. I know alot of us dont have access to a 10' boring mill so we have to make do. In the past and in a pinch, I have pre-machined the components of very large weldments prior to welding. With good results. If one takes time to set everything up and clamp solidly then stitch weld to keep the warpage minute, the results are satisfactory.

Ron

"Tyson S." <timbercutter@...> wrote:

So does anyone know of a type of steel that can be purchased that is
straight and clean. I know cold roll flat bar is really good stuff, but
what about square tube?

--- Leslie Watts wrote:

>
> Hi Hal
>
> I won't quarrel with your figures...they seem about right.
>
> The issue is the definition of specific stiffness...
>
> Steel has about three times the modulus of aluminum, but it is also
> three
> times the density!
>
> Specific stiffness is the ratio of those two parameters, so they are
> about
> the same.
>
> This is true for most alloys, hardened or unhardened.
>
> One way to think of it is an identically dimensioned bar of different
> materials.
>
> The material with the highest specific stiffness will ring with the
> highest
> note when struck.
>
> FYI the highest specific stiffness of the common metals is beryllium.
>
> OK? :)
>
> Les

=====
Check out my APRS digipeater:
http://map.findu.com/FIELDR



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