"DoN. Nichols" wrote in message
...
In article . net,
Boris Beizer wrote:
"Scott" wrote in message
roups.com...
The tools marked "525" are Blackalloy. It is a similar tool to the
others mentioned. Its advantage is its interrupted cut strength. Great
for hex stock in stainless. Its weakness is temperature shock. In
other words flood cool and keep it cool or grind hot and DON'T DIP IT.
Temperature shock will cause flaking on the cutting edge. Overheating
will not anneal it. In fact it can be brazed like carbide when it gets
to short or to make form tools. The starting cutting speeds are double
those of cobalt. It used to be made in NYC, NY. They had cards with
geometry and cutting speeds. It is most often abused by DIPPING IN
WATER when sharpening.


Well that's a very useful and important piece of information. I would
certainly have made that mistake. Now that you mention it, how about
Stellite and Tantung G . Do we treat them like HSS (and dip as we go) or
as
525 or what?

Based on information posted in the past three years or so on
this newsgroup, dipping HSS is not a good idea, either. I would not dip
it.

It is carbon steel which needs the dipping to prevent
overheating and tempering -- *before* it turns blue from the grinding
heat. :-)

HSS cannot take that kind of thermal shock and still maintain its toughness.
It's fairly tough but not that tough. You really shouldn't "dip" any kind of
hard steel.

As for Stellite and related superalloy cutting tools, they have a few
niches, but in general they don't fair well on the cost/performance scale.
They aren't hard enough to compete with carbide in hard materials and they
can't approach their cutting speeds. On modern machine tools, they're of
little use today.

However, someone mentioned something about non-rigid machine tools, and
that's probably a place where they do quite well, since they're fairly
tough.

--
Ed Huntress