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On Jun 14, 2:18 am, "Michael Koblic" wrote:

Make sure your cutting tool/insert is aligned on centerline.

Does this apply to all boring bars? I found one (carbide insert) with a
negative rake. This puzzled me and some research on the net suggested that
it should be used below the center. Is this wrong?


Michael Koblic
Campbell River, BC

When you are turning a outside diameter in the lathe , you want the
tool on the centerline of the part or very slightly below centerline.
The reason is that if the tool digs in, it is deflected down which
moves it away from the cut. If it is above center, when it digs in ,
it is deflected down and into the cut. Which makes it dig in more.

When boring everything is exactly reversed. The tool should be on
centerline or slightly above centerline. If it is below centerline,
if it digs in, it will move down and dig in more. I prefer slightly
above centerline. Because boring bars are more flexible than tool
used for outside turning. So they are very likely to deflect and if
above centerline they will not dig in more. That is true whether the
rake is positive or negative.

Dan
While that's of some concern, the biggest one is that boring requires
considerable relief, especially on small holes, where the radius of the part
is quite small. Running below center often yields dragging of the tool on
the front relief, which isn't acceptable.

Harold