On Oct 30, 3:37 pm, Jon Elson wrote:
Dom wrote:
This is driving me crazy. I've tried everything I can think of.

-Centre height OK.
-Blade not overextended.
-Insert OK
-Coolant on
-Reduced speed, increased feed
-Adjusted backlash on cross slide to minimum
-Saddle clamped
-Happens with different materials, and diameters

But I can't eliminate the vibration. It is really heavy, and is
causing clamping screws and the like to loosen.

It's making me feel like a complete idiot. I should be able to solve
this problem, but what's causing it?

Any suggestions, or should I just go and slash my wrists now?! g

Cheers, Dom.

Well, I used to have a light lathe (Atlas 10", then a Craftsman 12") and
had a lot of the same problems. Making things more rigid helped, up to
a point. Making sure the cutting tip is as close to being over the
compound swivel helps a lot, too. If you have a "lantern" type
toolpost, that cn become quite flexible.

Reducing speed may be counterproductive. You definitely want to keep
the feed steady, but sometimes speeding up and keeping the cut moderate
to prevent overloading the motor is helpful.

Now that I have a 3500-Lb 15" Sheldon, I don't have these problems at
all, using essentially the same techniques. So, it has to be rigidity
of the machine. If flexibility of the lathes's spindle or bed is the
limit, then nothing you can do outside changing the whole lathe will fix
it. I have seen pictures of "gooseneck" tool holders that were designed
to flex AWAY from the cut, preventing the chatter from building to
enormous amplitude. Other than surfing eBay, I have no idea where to
get such a thing today.

Jon

I watched my 10X24 Jet lathe walk on the floor since 1976. Then last
year I bolted it too a 2 inch thick steel plate, now it will cutoff
without chatter. I was told to also make a very heavy stand with 4
inch square tubes, and bolt to the floor. Have not done this but will
in the future. currently it is on a HF sheet metal stand intended for
a 12X36 lathe. Not bolted down, but leveled.

I also have a 5000 lb. 18X40 lathe, and it will break tooling before
it ever chatters. Let me tell you, the D size quick change was never
intended to work with this beast, I've several times now have seen the
fine adjust screw bend, and the tooling slide down on the dove tail.
You really have to over tighten the wedge clamp, especially when
making gouging cuts into the end of a solid round. I was trying to
make a large (4 inch) piston at the time, gouging out where the crank
would be. Not making killer cuts.

Ignator