Re: [CAD_CAM_EDM_DRO] Re: BYO CNC Lathe ?

bswim_99 wrote:

> People don't realize how much torque lathes put out or the amount of
> cutting pressure generated.
> Unlike a mill where your tool gets some relief as the cutter spins, a
> lathe is always under stress of cutting.

I guess that is the case..........
I am talking about some IKO's that the rail alone stands about 1" high though, not some of the smaller 3/8" high/wide stuff. I would probably mount these to a piece of 1-1/2" thick cast aluminum
for a "bed". You have to admit, Holding a set of big IKO/THK's in your hands makes one feel pretty invincible ! But the reasons so far would indicate that the current sliding gib concept would add
lots of chatter stopping mass to a machine. I suppose transfering all of the related "lathe" action into all the ball bearings would have some unfortunate results. I will have to wait and see the
photo posted by Peter H.

If I could only afford one of those Prazi's.... they look like a nice one to retrofit. Maybe I should just save up a little longer.

thanks,

Chris L

>
> I could see stuff bending or flying apart unless you used some heavy
> cast iron for the base.
> The smaller Mazak CNC's lathes use replaceble slides for the ways.
> But they sit on a tremendous amount of cast iron. They cruise too.
> The one I ran did 1200ipm.
>
> --- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
> > Chris L wrote:
> >
> > > Ok,
> > > I've taken an interest in purchasing a small lathe to convert to
> CNC.
> > > Everything I look at though, spooks me off a bit. The Taig...To
> Small.
> > > The Sherline, To Pricey. The Imports ? Well, we picked up a Jet
> 9x20 for
> > > a quick and dirty machine and I was not very impressed. I did not
> think
> > > one should build a machine like that out of such soft metal. You
> should
> > > see how wobbled out the wrench holes are in the spindle from
> taking the
> > > chuck off ! Scary! I do not think I would ever cnc that thing.
> > >
> > > So, I began to think about building my own. (BYO)
> > > Is there any reason why I could not use some good sized THK-IKO
> style
> > > bearings for the rails ? Why do all lathes have the typical beds
> with
> > > sliding gib concepts anyhow ? Linear bearings should work, No ?
> >
> > For rigidity. The cutting forces are surprisingly large, even on
> pretty
> > small lathes. Secondly, and tendency to vibrate will set the whole
> > machine ringing like a bell, and cause horrible chatter marks in the
> > part, or even rip the part out of the chuck. There has to be an
> important
> > reason my Sheldon lathe weighs 3000 Lbs! Even the bed of that lathe
> > can be made to vibrate without a great deal of effort, and it is
> about a
> > foot square in cross section (two 2" wide vertical beams with cross-
> > struts in between) and weighs at least 1500 Lbs for a 6' length.
> >
> > The Unimat was made like this, and I have heard horrible stories
> about
> > vibrations in that machine.
> >
> > >
> > > I could even put the Tailstock on the same rails with a separate
> > > leadscrew and handwheel instead of having the tailstock made in
> the
> > > conventional way. That sounds alright.
> > >
> > > I could come up with a really neat spindle with a really large
> thru hole
> > > instead of all this too small stuff. (I knew I would someday find
> a use
> > > for front wheel drive cars... The front hub and spindle ! I could
> keep
> > > my GM lathe ALL GM !)
> > >
> > > I thought I could probably use big chunks of Billet aluminum for
> the
> > > headstock and tailstock but was worried about not getting enough
> mass.
> > > But I suppose it would still be as good as a Taig or Sherline.
> >
> > No, I suspect if you use unsupported rails, it would actually be
> worse
> > than a Sherline! With supported rails, it might be a little
> better, but you might
> > have rapid wear on the rails or bearings.
> >
> > Jon
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://www.jobshophomeshop@yahoogroups.com I consider this as a sister site to the CCED group, as many of the same memembers are there, for OT subjects, that are not allowed on the CCED list.
>
> Post messages: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> Moderator: jmelson@... timg@... [Moderator]
> URL to this page: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> bill,
> List Mom
> List Owner
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/