On 2019-06-29, John B wrote:
On Sat, 29 Jun 2019 19:18:24 -0400, Ed Huntress
wrote:

[ ... ]

Hi John. HSS indexible inserts are available. Even Amazon has some.
I've seen them offered with or without a chip groove and, IIRC, with a
moderate amount of relief or no relief.

Useful.

Granted, those variants were things I saw years ago, but I think
you'll find that a few different types are offered, and some look
exactly like typical carbide inserts.

Probably true as I've been totally out of the trade since 1972 and
when I left we were still using HSS. In fact, thinking back, I can
remember only one time we used a carbide tool to turn something and it
was a hard valve insert in some sort of special valve and the HSS just
wouldn't make a compete cut. (Damn! that was nearly 50 years ago :-(

Yes, there are materials where carbide is the better choice.

But I think if I were to buy a hobby lathe today I'd still go for HSS
if for no other reason than it lets you grind all sort of special bits
for various projects. Back in the day a machinist would probably have
ten or a dozen tool bits in his tool box that he had ground for some
sort of special project over the rears.

There are tradeoffs. HSS for specialized tools/purposes.

Carbide inserts and a quick-change toolpost for repeated
operations. The inserts can be rotated to give two, three, four, or up
to six different cutting corners, depending -- and each time you do
this, you don't have to re-calibrate the dial to the new length of the
bit -- that is what "indexable" means. Especially useful with CNC and
automatic tool changers, but useful enough with a lathe with a
quick-change toolpost, and remembering the zero point for the tools
where the diameter of the turned workpiece is important. And the
inserts are made sufficiently precise so the zero is maintained when you
finally wear out all the points on the insert and replace it with a new
one. :-)

I use carbide inserts most of the time -- but still grind
special tools at need -- including ones to cut ACME threads a bit too
big for the insert tools which my lathe can handle.

And, if there was a bench grinder in the shop you never had to worry
about dull tools :-)

Agreed -- but you did have to re-zero the dials after each
re-sharpening. :-)

Enjoy,
DoN.

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