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

Hi Tyson

Tubing, square or otherwise, has much higher torsional stiffness
for a given weight than I bar or channel.

Cold rolled or drawn materials are usually very accurate and clean, but have
large residual hoop stresses due to the forming process.

Hot formed structural shapes have much lower stresses due to the high
forming
temperatures, but usually have a heavy mill scale from oxidation. This can
be
easily removed with hydrochloric acid.

I use hot formed ASTM A 513 welded flash in low carbon tubing and ASTM A36
hot rolled solids for minimum deflection during machining or welding.

The 513 has some residual hoop stress but the effects are minimal with 2
force
menbers.

Les



Leslie M.Watts
L M Watts Furniture
Tiger Georgia

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-----Original Message-----
From: Tyson S. [mailto:timbercutter@...]
Sent: Monday, October 25, 2004 8:42 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel
vs aluminum



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 <leswatts@...> 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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