2. Cobolt vs ordinary HSS. What does Cobolt provide other than bigger

Cobalt will hold an edge longer. When turning tough material like 4140
I choose Mo-Max cobalt toolbits. I remember trying a chinese import
toolbit and it would dull quickly. MO-max cobalt kepts on cutting.

I use just about any toolbit for aluminum and brass. Name brands seem
to stay sharp longer but I have never done any testing. I use whatever
is handy.


3. Stellite vs. HSS /Cobolt. Advantages, disadvantages, preferred metals
to use on, contra-indications, special problems and issues.

Can't buy Stellite, so I buy Tantung, which I believe is similar.

I tend to use Tantung for heavy roughing cuts. Tantung wants to
run 100-300sfpm and really removes the metal. I switch to a sharp
regular or cobalt HSS bit for finish cuts.

5. Any special issue, for a given metal to be cut with respect to rake,
relief, etc? for each:: HSS, Cobolt, Stellite, carbide.

I was told to grind Tantung toolbits with angles suggested for carbide
(which are less than the angles for HSS) because I was having problems
with the toolbits chipping. However I think my problem may have been
caused by using too slow of a speed and too much feed.

chuck