I sent this once before, but it doesn't seem to have made it to the
newsgroup.
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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