Re: [CAD_CAM_EDM_DRO]doodling with ideas

Bill,

There was an article on this subject in Modern Machine Shop several
years ago. The limitations Joe mentions are the tip of the iceberg, and
are more easily overcome that the issues of geometry.
Think of turning a square. With the tool on spindle center, and one
corner right at the cutter edge, as you begin to start the next side you
will see that the tool must have a clearance angle exceeding 45 degrees!
As the cutter passes the half way point on the side of the square, it
will, just before reaching the far corner, have in effect a 45 degree
negative top rake. This ultra extreme range of conditions is more than
conventional tooling can take.
I'd say this article appeared 4-5 years ago, ball park. Back then, they
were having trouble just coordinating the cross slide to the spindle
with an acceptable level of following error. Consensus was that squares
were out of the question, but they did believe hexes could be done with
more work. However, this is the realm of production and seconds count.
There are other, faster ways to do these tasks.

There are special lathes that produce hexes by orbiting a tool around
the part in elliptical paths. These don't produce a true flat, but come
close enough for real life. Volume production only.

There is also an attachment available for vertical mills (manual type)
that will cut internal and external hexes, ellipses, and other shapes.
Used to have a brochure on it, but I do recall it's an expensive sucker.

Jon