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

Posted by Leslie Watts
on 2004-10-25 17:29:33 UTC
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

Leslie M.Watts
L M Watts Furniture
Tiger Georgia

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http://www.lmwatts.com
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-----Original Message-----
From: Hal Eckhart [mailto:hal@...]
Sent: Monday, October 25, 2004 8:19 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel
vs aluminum



On 10/25/04 6:23 PM, Leslie Watts wrote:

>Aluminum and steel are virtually identical in specific stiffness.

I don't think that's true. The modulus of elasticity for steel is
29,700,000 psi and it's 10,000,000 psi for aluminum (this will vary
based on type and temper, but it's the best info I can find). For
example, a 2" square steel tube with a 1/8" wall would deflect 0.11"
with 100# load in the middle of an 8' run. For aluminum, it would
deflect 0.33".

This info is from the cheesy calculator I hacked together at
<http://metalgeek.com/static/deflection.php>.

If you want to quarrel with my conclusions, I've posted my sources
there. I am NOT an expert on this, although I do bend a lot of metal.
And my limited testing seems to support the accuracy of the calculator.
But I'm certainly open to other ideas.

And one note about 8020. I've used it, although I wouldn't recommend it
for framing (for a hobbyist). Unless you're going to be reconfiguring
it later, it's awfully pricy. However, they do sell a slick little
sliding dohickey for it that seems like it would work fine for a plasma
Y axis.

Hal Eckhart - Casa Forge - Minneapolis MN - <http://www.casaforge.com>


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Discussion Thread

Marcus and Eva 2004-10-24 10:56:52 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts Robert Campbell 2004-10-24 11:15:23 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts Tyson S. 2004-10-24 12:01:22 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts Robert Campbell 2004-10-24 12:41:33 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts Chuck Rice 2004-10-24 23:05:54 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts Bob Muse 2004-10-24 23:15:33 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts turbulatordude 2004-10-24 23:16:16 UTC Re: sourcing motion control parts turbulatordude 2004-10-24 23:37:26 UTC Re: sourcing motion control parts aerowright 2004-10-25 07:23:21 UTC Re: sourcing motion control parts Stephen Wille Padnos 2004-10-25 07:45:04 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts R Rogers 2004-10-25 07:48:13 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts turbulatordude 2004-10-25 09:58:45 UTC Re: sourcing motion control parts - steel vs aluminum MateuszGoÿffffb3ÿffffb9bek 2004-10-25 14:07:40 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum Leslie Watts 2004-10-25 15:24:22 UTC RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum Hal Eckhart 2004-10-25 17:18:57 UTC RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum Tyson S. 2004-10-25 17:28:19 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum Leslie Watts 2004-10-25 17:29:33 UTC RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum MateuszGo�ffffb3�ffffb9bek 2004-10-25 17:36:38 UTC RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum Tyson S. 2004-10-25 17:42:19 UTC RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum Hal Eckhart 2004-10-25 17:51:19 UTC RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum Leslie Watts 2004-10-25 18:02:22 UTC RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum Leslie Watts 2004-10-25 18:42:52 UTC RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum turbulatordude 2004-10-25 19:26:00 UTC Re: sourcing - steel vs aluminum - straightness R Rogers 2004-10-26 06:43:36 UTC RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum Robert Lyman 2004-10-26 07:41:28 UTC RE: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum Patrick J 2004-10-26 08:12:23 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum R Rogers 2004-10-26 08:41:37 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum Patrick J 2004-10-26 08:59:40 UTC Re: [CAD_CAM_EDM_DRO] Re: sourcing motion control parts - steel vs aluminum turbulatordude 2004-10-26 09:18:49 UTC Re: sourcing - steel vs aluminum - stree relieving Robert Lyman 2004-10-26 10:24:20 UTC Re: - stree relieving turbulatordude 2004-10-26 10:41:58 UTC Re: - strees relieving R Rogers 2004-10-26 10:56:42 UTC Re: [CAD_CAM_EDM_DRO] Re: - stree relieving Robert Lyman 2004-10-26 11:09:06 UTC Re: [CAD_CAM_EDM_DRO] Re: - grinding. Leslie Watts 2004-10-26 11:37:03 UTC RE: [CAD_CAM_EDM_DRO] Re: - grinding.