On Sun, 22 Mar 2009 17:16:03 -0400, Ed Huntress wrote:

"Errol Groff" wrote in message
...

Two of my students are building model hit and miss engines. The
drawing calls for stainless steel for the connecting rods but does not
specify what grade. The part will be made from .4375 diameter rod
stock.

Suggestions please on what grade to use keeping in mind that they have
no experience with S.S. so machinability is important. Will probably
order the stock from Mc Master Carr and they list a bewildering variety
of grades.

Thanks,

Errol Groff

It seems strange that stainless is called for at all. Is there some
reason for it, or is it some designer's random idea?

Stainless is slightly less stiff than other steels; it's not
particularly strong in the likely grades you'd use; it's subject to
stress-corrosion cracking; the austenitic (300 series) grades make truly
lousy bearing surfaces; it costs more...what in the heck is the reason
for it?

Being cynical, I would guess that the original designer called it out
"'cause it's purty when it's all shined up nice".

Or he had it on hand, or he had strange notions about SS, or he wanted to
learn how to machine it, etc.

--
http://www.wescottdesign.com