Re: [ATM] Aluminium or stainless steel?

[Richard <cnc@cncservo.co.uk>]

Hi Gary,

Saturday, May 7, 2005, 6:57:01 AM, you wrote:

GM> As part of a mount I am making I need to determine whether to use (from
GM> materials already at hand) a 50mm stainless steel shaft, or a piece of
GM> aluminium tube 85mm in diameter with walls either 5mm or 10mm thick.

GM> I need to be able to support a load of around 15kg at a distance of 500mm
GM> from the nearest bearing. One end is supported and the other end is free.

Stiffest is the thick walled ally, next the thin walled ally,
worst is the stainless. I've assumed E=70GPa for the 6068 ally
and 180GPa for 304 stainless, but modulus of elasticity varies a
lot for stainless, from 110GPa up to 240GPa, depending on type.

Deflections :

50mm stainless : 0.113mm
85/5mm  ally   : 0.088mm
85/10mm ally   : 0.053mm

All three have small internal stress, but I can't comment on
suitability without knowing what deflection etc you are happy
with. Personally I'd want to do the sums on the bearing...

-- 

Best regards,
 Richard



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