I am doing a project where I need to turn an eccentric on a shaft.
Being a little idle and not wishing to set up a 4 jaw chuck I wondered if anyone had a written a wizard?

Clive

Never seen one but i'd be interested too. Wouldn't milling on a 4th axis be better for that?

The tool cuts concentricaly about the lathe center, so you need to shift the work.
Thus no wizards.
RICH

I am doing a project where I need to turn an eccentric on a shaft.

You would need a hell of a fast X axis on your lathe for doing that I would think.
Hood

You say that it would have to be very fast in X but is it not similar to the way a copy lathe worked also they made rifle stocks at springfield armoury in Massachusetts by a similar method in the 1800s (not using CNC though, not even an early version).
I am sure that some smart person could do the maths.
Is it also not the same sort of control you get when cutting threads?

Clive

PS. I am not being contentious just interested.

In one revolution of the material your x axis will have to move to the min and max dia of your eccentric so unless you had a fairly slow RPM I would think the X would need to be rather rapid, especially on acceleration. But maybe I am just thinking about this the wrong way.
Hood

Granted that the revs would be slower than normal  but the acceleration would be gradual and the changeover point would be at the point with the slowest movement.
Just thought of the downside,  backlash or would the compensation take it out

If this is for cutting metal especially if using carbide then I would think you would need to keep the revs up so that you get the surface speed required for a good cut.

For comp to work I think you would have to look at it another way, ie have the spindle set as an axis and for that your spindle would need to be a servo or stepper.

Hood

have a look at this vid.

slow going, needs accurate control

http://www.youtube.com/watch?v=CVpeChtENEY&feature=related

JB

Even if you work out the X axis speed issue, producing the gcode to cut the eccentric would be something far not obvious.

Daniel