"Tim Wescott" wrote in message
...
On Thu, 06 Oct 2011 10:01:29 -0700, Denis G. wrote:

On Oct 6, 9:21 am, Rosie wrote:
My CNC Cincinnati Hawk 150 started to make a big noise/vibration while
Part-off. I make the machine turn counterclockwise with the tool upside
down. Somebody told me the problem could be (this is only a
possibility) the ways are worn because it's not a normal/good practice
to use the CNC that way for Part-off.

What do you think about ?
Has somebody had this problem?
What do you suggest, changing the ways is a very expensive test to do,
I have a small machine shop and I need this machine for my biggest
customer.

Thanks very much

My experience if only with manual machines, but normally the forces push
down on the tool post and down on the ways. Most lathes are designed
that way. If I understand what you are doing, the forces are pulling
up on the tool post and trying to pull the tool post up off the ways.
That may be the cause of your problems.

The only time that I've heard of using the lathe in reverse rotation is
for threading, so the tool will be moving away from the work piece (so
you don't have to stop the lathe just in time to prevent breaking
anything). And wherever it was that I read about that, the author was
also advising that you use a left-hand tool on the back side of the work,
so that the tool would still meet the downward-traveling face of the work.

--
www.wescottdesign.com


That is an old machinist's trick when they are using a machine at its upper
limit.
Most of the machines with Tee slots in the cross slide have, as an
accessory, a rear tool holder for parting off. The force is transmitted more
directly to the ways without going through the compound so there is less
opportunity for " looseness"
I don't know anthing about CNC usage but I would expect the same rules to
apply