Steve Smith wrote:

I sent this once before, but it doesn't seem to have made it to the
newsgroup.
---------------------
There are lots of threading inserts, and the several catalog pages I've
looked at to try to understand them don't do a very good job. The
turning inserts make a lot more sense than the threading ones.

So first, can anyone point me to a reasonable explanation of how the
inserts are numbered (threading, not turning)?
Are threading insert brands compatible with each other? For instance,
can I expect to use company A's insert in company B's holder?

And in the too convenient to be true department, can I use a triangular
threading insert to cut internal threads with my insert boring bars?

I could make threading insert holders, but don't know the angles and
such, how much it varies from insert type to insert type, etc.

Thanks,
Steve

Using a standard 60 degree cutting insert you run into the problem of
relief for the helix angle. In other words, the bottom of the insert
will drag on one side of the thread. You could grind relief in the
insert and check it on a already threaded bolt. I would go with a
standard threading insert. laydown inserts are nice because they form
the full thread shape but you need a different insert for each pitch.
Single point tools seem to work better for manual threading. You can buy
an E type brazed tool for very cheap prices but make sure you check it
with a fishtale gauge. I had some I bought once that were ground wrong.
They were kennametal from MSC. I went to the store and all the ones in
the box were screwed up. Single point inserts are nice because if you
break the insert you just put in another and you are already in
position. You got to watch that the point does not get broken off. The
thread will look nice but the root will not be completely cleaned out
and you will over cut the thread if you are using a thread gauge to
check the fit. If your lathe has a thread stop it makes it a pleasure
to cut threads. If not it becomes a little more of a challange. There
are a lot of good sites on the web on threading... search "double depth
threads."


John