Re: [CAD_CAM_EDM_DRO] Depth of piece

Roland Jollivet wrote:

> Hi
>
> Can anyone tell me how a cnc machine references length in a collet chuck?
> Example. If I have a number of 1/4in x 1in rods, and I want to round the one
> end. The final, total length must be exact.
> Manually, I would face both ends, measure it, chuck it, and reference to the
> protruding end, then round it
>
> In a collet chuck, the piece is pulled in with the chuck, so a back stop
> can't be used?
>

Specifically for 5C, but probably other collets as well, there are back
stop devices. They thread into the back of the collet and have an
adjustable and lockable rod to stop the work. Since the rod is attached
to the collet itself, it won't bind or force the work. As long as the
work is of consistent diameter, you will get excellent repeatability,
and if the back side of your workpiece is turned smooth, you should get
a repeatable length to a few .0001" at the worst.

> So how would a cnc lathe using a collet chuck(and front loading) round a 100
> pieces? What is the procedure?
>
> I think that maybe the answer is that a CNC machine with collet chuck feeds
> the work out, so it would;
> - turn the end round
> - part off
>

Yup, that's the bar feeder way to do it. it is hard to get rid of the
little pip on the end when you part off, and you may have to make a
relieving cut first before the final parting off cut. A thin
parting-off tool usually doesn't give a great surface finish, it wanders
a bit.

Jon