Need Help!- How Does?

[kawazuki]

A CNC'd lathe work out the diameter of an object its turning? This is puzzling me and I just can't fathom how if you were to start with 2" dia roughly centred stock and had to turn it down to 1" finished that the machine realises its removing a variable amount to get down to the 1"
Is the spindle axis centreline set in stone - never to be varied and thus offsets are always able to be calculated?
If this is it..........how is that located as the tool cutting point will always be at a different offset relative to the centreline? Confused???

[hoss2006]

You have to set the tool up just like you would on a mill, touch off on a surface and reset the DRO.
You can take a skim cut on the OD, measure, then move the X to the centerline and reset to zero if that's what your program uses for the origin.
Some use an origin that is above the part, say at 2.500 inches. It's up to you.
hlombard on my forum just made a lathe probing screenset that uses parts of my probing set.
you can download it there.
Hoss

[muddobber76]

Your spindle centerline is set to zero for the work cordinate/machine origin; this is relative to the turret or tool post. The machine should be set up so that the dead center of your drill/boring bar holders are on center line when you call a tool to go to X0.0. All tools will be an offset of this value. So a drill,center drill,tap,etc., will be set as X0.0. All other turning tools will be a calculated amount that deviates from center line. The cnc control will do this for you.
With the machine knowing the tools location relative to centerline, you tell it a start point(diameter), an end point (diameter), and depth of cut(decimal value) to determine how many passes you make to remove the stock.
Very simple. When you watch someone set and run a tool it will make sense.

[Switcher]

Just don't offset your X-axis, for the drill.