On Wed, 26 Jan 2005 17:29:47 -0600, "John L. Weatherly"
wrote:

Tom Gardner wrote:

Could that end have been welded before?

It was chattering near and on the weld that I laid. I would have thought
that it was the weld but the chatter started about an inch before. My
money is on harmonics. I wonder what steel these things are made from.
Seemed a bit harder than regular mild steel.
Having turned lots of long shafts over the years as a lathe man
chatter sometimes responds to increased tool pressure and sometimes to
decreased too pressure. It seems odd I know. I see you have finished
the shaft so maybe this will help another day. If the shaft is stout
enough, and your setup rigid enough, using a negative rake tool can
work very well. A fairly high feed is also usually needed with the
negative rake tool. On the other hand, a limber shaft, especially if
it's a tube, can benefit from very sharp tools, and a finer feed.
However, you must be careful to grind the tool such the shaft will not
tend to ride up on the tool. One job in particular that I used to run
were tubular drive shafts for turbine engined light planes. These
shafts were made from 4340 and were heat treated to about 38 Rc. The
wall thickness was about .100 and the O.D, about 1,75 in the middle.
They were about 44 inches long. Using a sharp carbide tool with a ,004
or .005 radius on the tip and spinning about 700 rpm worked the best.
I had to use enough cutting oil to keep the shaft lubed enough that I
could wrap my hand around and gently squeeze the shaft while turning.
ERS