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.

Harold and Susan Vordos wrote:
"Boris Beizer" wrote in message
ink.net...
1. On a hunch, or perhaps it was something someone said earlier, I
checked
those stellite bits and found that they are not magnetic. So back
to the
bit bin and pulled out all the non-magnetic bits. It included:

a. All the stellite bits and blanks.
b. Some called "Tantung G."
c. Some called 525.