On Mon, 11 Jun 2012 14:20:39 -0700, "Bob La Londe"
wrote:



"Boris Mohar" wrote in message
.. .


http://www.youtube.com/watch?v=mRuSYQ5Npek&hd=1
Regards,
Boris Mohar


Very educational. What type of distance of travel were we looking at there?
It seemed like in all cuts it would build up a wedge of garbage on the
cutting edge and then eventually roll it under or deflect the cutter
creating a larger imperfection in the surface. For finer finishes would
that mean atleast in cnc you could use a form of peck turning? Its hard to
gage in that video, but the distance between the more substantial
imperfections seems quite short.

Regardless, very entertaining.

Thank you.
Bob La Londe

That pattern was first observed at Carnegie-Mellon Univ. in the 1950s,
and by Dr. Eugene Merchant at Cincinnati Milicron. This video is much
better than the films they made, showing close-up at high resolution
how the compression-failure/shear-failure mechanism works.

In very fine cuts, it's mostly shear. At deeper cuts, it's often
compression failure, then shear. In some materials it's mostly shear
even with deep cuts.

Some of the interesting work they did was taking spark photos of
ultra-high-speed machining (over 10,000 sfm). For that, they shot a
..30 cal. bullet across the edge of a cutting tool. The failure
mechanism for that is extrusion/shear, and cutting forces per cubic
inch of metal removal actually go down. The chips are much longer than
the path of the cutter in the material, with the chip extruding far
ahead of the cut.

--
Ed Huntress