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!

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