On Tue, 14 Oct 2003 16:41:41 -0500, Jon Elson
wrote:



Bruce Simpson wrote:

I've done a lot of machining on stainless in recent years and found
that once I became accustomed to things such as work-hardening, using
low speeds and agressive cuts, it's not so bad.

However, yesterday I encountered the piece of stainless from hell.

It laughed at my M42 toolbits, rounding off the edges within moments
of contact -- no matter that I'd ground back the surface to remove
possible work-hardening, that I used good quality cutting lube, that I
had sharpened and honed the tool perfectly adn that my SFM and depth
of cut were what I normally use for SS.

Even carbide tooling doesn't cope well with this stuff (I've gone
through three inserts already when normally they last ages on SS).

I guess this is the price you pay for picking up bits of scrap from
time to time rather than buying a known alloy off the shelf.

I don't know what alloy this is but it's non-magnetic (austenitic?)
and, based on its awful hardness, certainly doesn't seem to be 303,
304 or 316.

Maybe it's not SS at all but that most elusive of all alloys --
impervium!


I think you are getting warm! It sounds like hard Chromed shafting. It
is nearly
impossible to machine, but can be ground nicely. It may look like SS, but
one giveaway to some pieces is the mirror ground finish.

Jonm

Got me. I did get some SS that seems to have rocks in it from a
dumpster. The other stuff seems to be fine , but makes me wonder why
they tossed 20' lengths of SS.

BTW, I stopped by that dumpster today and it was gone along with the
lazer stuff in the shop. The doors were wide open and not a machine
in sight. There is another building behind that , that the same guy
owns , but there was a cop setting right by where the dumpter sat and
I didn't want to look around to much. Wonder if the biggest machine
shop in town folded . The guy had given me a complete tour of the
place and I only saw two vertical mills the rest where CNC and cool
bolt makers that heat them up with elec. Time to find the guy , but
I'm busy.

Anyhow, lost my best dumpster diving place even though some of the
stuff should be in the dumpster.