Re: turning center retrofit for home shop?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:

> I looked very seriously at a couple of CNC turning centers which had
> abominably out of date controls before buying a big manual lathe
> project. One of the reasons behind my decision was that most turning
> centers, especially the ones that came up on eBay, had very short

beds. I don't believe I EVER saw one with more than 24" of Z travel,
and most were in the 10 - 12" range. Now, MOST of my turning would
fit those machines, but every once in a while I have something longer
to turn, and I really didn't want that limitation.

>
> I assume you know that EMC has a problem with lathe turning.
>
> Jon

I've got 5 turning centers and can handle up to 36" between centers,
but about 90% of the work I do can easily be handled with 8" or less
of Z travel. Given the difficulties and expense of putting a ball
leadscrew in a good sized lathe, here's a wacky idea I've been kicking
around for adding to a neat little programmable turret lathe I have
that doesn't have contouring capabilities. I'll explain it as if it
was going onto an engine lathe.

Since the entire compound is easily removable from most engine lathes,
just build or adapt an X-Z slide assembly in place of the compound and
CNC this part as opposed to the entire machine. The original
functionality of the lathe would be retained in its entirety, and for
short chuck work the carriage and cross slide could be locked into
position and everything would be done with the X-Z slide. For work
longer than the controlled Z travel, the regular lathe functions could
be used, and in the case of features requiring contouring somewhere
along the shaft, the carriage could once again be locked down and
these features turned via CNC. In my experience, 6 to 8 inches of Z
travel in the slide assembly would cover about any feature commonly
found in turning work that isn't readily do-able via manual turning.

Further thoughts about this idea, including those of why it might not
work, are welcome.