Re: [CAD_CAM_EDM_DRO] Re: BYO CNC Lathe ?

Hi all:
I think a do-it -yourself lathe with linear ways is an eminently doable
project, provided the linear ways are hefty crossed roller ways mounted onto
something solid.
Have a look at the Omniturn website; there is a photo of a stripped machine,
and it's pretty simple.
A far better choice however, is to sabotage something like a Hardinge
chucker.
You get a decent base and a nice accurate spindle from which you can build
a quality machine.
They're pretty cheap these days on E bay.
Cheers

Marcus

----- Original Message -----
From: "dave_ace_me" <davemucha@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, March 15, 2002 5:18 AM
Subject: [CAD_CAM_EDM_DRO] Re: BYO CNC Lathe ?


> There is a lot to be said in favor of mass. There is also distance
> involved with the torque calculation. a wider spread will yield
> higher torque. I think the boxy, squareish bed of the lathes is
> there for torque and strength. But they design those units for any
> work, not a product specific design.
>
> There is a link regarding a CNC lathe, linear shafting, about 1.5
> inch dia I think, spread about 18 inches apart. very well made
> unit. but I am sure the mass of the table is there to HOLD that 18
> inch spread, or vibration and the harmonics will surely make
> themselves known.
>
> This week, I took a 0.01" deep cut on a 2" solid cold rolled steel
> bar 22 inches long. If I took 0.015" the vibration took over.
> 9"x20" South Bend lathe, chuck and a live center to hold it.
>
> Dave
>
>
>
>
> --- In CAD_CAM_EDM_DRO@y..., "bswim_99" <bswim_99@y...> 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. If you're making a 6" long
> > cut, that pressure is going to build as you cut until you disengage
> > the cutter from the part.
> > 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
>
>
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