Re: ATM Cutting Stainless Steel

["J&S" <jsstars@worldnet.att.net>]

Hi Art and All,

From: Aart Olsen <aolsen@prairienet.org>
>Does an abrasive disk cut stainless well?

     Yes. A high speed cut-off saw with abrasive wheel will make quick work
of stainless steel tubing and round and square stock. This is fine (IMHO)
for chopping off a piece of stock for further machining. The drawback is
that the heat generated in the zone of the cut discolors the material
(brown-purple-blue-black) and I assume also alters the alloy a bit near the
cut. This is no big deal if the area near this brutish cut is going to
machined away, or even if the part is to be painted and hidden away
somewhere.
     I have not had experience in trying to cut plate stainless with a
cut-off saw though. I've always used a bandsaw (or hacksaw) for anything
other than thinwall tubing or small diameter round and square stock. If you
give it a try, be sure to clamp your work well and wear eye protection and
ear plugs.
     I used to spend my days in a shop where part of our duties were
establishing standards and measuring the tensile strengths of various steels
(stainless mostly) and other tough alloys. This required the making of
identically sized and shaped specimens (roughly hourglass-shaped and
threaded on each end). Strain guages were attached to the specimens which
were then pulled apart in a powerful hydraulic machine while data about
stretch and fracture of each specimen was recorded. This was done at a wide
range of temperatures down to cryogenic. The blocks of metal these specimens
were cut from ranged anywhere from 4 to 18 inches thick.
     Naturally, while making the specimens, it was necessary to handle the
material such that no altering of alloy or grain structure of the metal
occurred, so we cut the raw blanks (prior to applying the lathe work) out of
the stock to be sampled using the most non-destructive method: a band saw.
     On the toughest metals (stainless, inconel, invar) we ran this saw's
blade (regular old HS steel band) at around 1 foot per second with a
constant coolant flood (petroleum-based cutting oil). The guy who spent most
of his time working on these specimens typically ran that saw about 15 or 20
hours per week. The rest of us used that saw to cut off large diameter (7
inch) stainless round stock for other projects on a regular basis. If I
remember correctly, it typically took about 15 or 20 minutes to cut through
a 7 inch piece of 304 or 316 stainless roundstock.
     The point of this long-winded story is this: in the three years I
worked in that shop, I only remember having to replace that saw's blade once
or twice. The correct speeds and feeds will insure long tool life and a
happy workpiece.

>I have a piece of stainless
>sheet, 3/16 inch thick, that I want to cut up to use for mirror cell
>triangles, and round stainless rods 3/4 inch diameter for the levers
>supporting the triangles.  I was thinking also of using the chop saw to
>cut flats on the ends of each rod, to recess the triangles slightly so
>they won't sit so high and to lower the telescope center of gravity a
>bit.  Too risky?

     Well, we all do what we want, but I'd recommend saving the stainless
for an application where you really needed it and using a lighter, easier to
work material for the mirror cell parts, like aluminum, primarily because of
the thermal mass all that stainless is going to represent. Aluminum will
cool off MUCH faster than stainless. Guaranteed!

>Can I do the flats with a grinding wheel?

     Yes. It shouldn't be a problem.
     Sorry to be so long-winded, but I thought my experience with the stuff
could help someone get a better feel for the nature of it, since it's been a
topic lately.

- Jim S.
Colorado