Jon Elson wrote:

Thanks. I think I will make a couple of holders that hold the
triange insert "backwards", with the flat side almost parallel
to the spindle axis. One just a little left, one just a little
right. With these, I could cut both left and right faces,
turn the diameter, and make steps to one side of the cutter.

Did you read the whole article and check out the pix?
http://www.metalwebnews.com/howto/toolholder/fig7.html
shows a set of three. I have never missed having any different angles
but I have a square tool post can swing at any angle to the compound
slide. This lets me set up for both turning and facing without moving
or changing the tool.

The holder needs to be a little narrower than the face of the insert.

Indeed! A sharp point 3/8" IC insert is 0.650" on the face. A TNMP321
is a little less due to the rounded point but still wider than 1/2".

Ted