Re: Swiss turning conversion

Chris,

The only practical guide bushing material is a carbide liner in a
collet like affair which can be slightly adjusted for stock
diameter. These can be stationary (non-rotating) or rotating. The
bushing has to be constantly flooded with a lubricating/cutting oil.

One major downside of Swiss type machines is the stock has to have a
high precision diameter. Any looseness in the guide bushing will
show up in the workpiece. Any oversize in the stock and it'll jam
the machine.

Almost exactly what you're describing has been done in high
production wood lathes for small parts. They're called automatic
variety lathes.

Instead of trying to adapt this concept to conventional lathe, how
about a CNC conversion of a cam operated Swiss machine? As far as
lathe conversions go, it'd be fairly straight forward. Besides that,
cam operated Swiss machines are dropping in price like rocks....no
demand because nobody knows how to set them up and run them anymore.

Doug

--- In CAD_CAM_EDM_DRO@y..., stratton@m... wrote:
> A "Swiss-type" cnc lathe uses a guide bushing to support the work
at a
> constant small distance from the cutting tool, and feeds the
workpiece
> through this instead of having a moving carriage.
>
> Contrast a conventional lathe, where the distance between supports
> (head/tail stock, steady rest) and the cutting tool is constantly
> changing, leading to large and variable deflection. For turning
down
> long constant-diameter sections one can rig a follow rest to travel
a
> short distance behind the tool.
>
> But what about for long tapered sections? By putting a similar
> structure on the headstock side of the carriage, could one
temporarily
> gain the advantages of the swiss setup, even on tapered pieces?
> (for one-offs of course - no need for bar feed)
>
> What type of guide/rest would be better? Bronze fingers like on a
> steady/follow rest? Ball bearings on fingers? A cylinder of bronze
> bearing stock, bored to match the workpiece, either fixed or running
> in its own ball bearings?
>
> If the lathe does not have the ability to make the cut to finish
> dimensions in a single pass, could the rest be spaced a short
distance
> form the tool (like 3/4") and the lathe be programmed to cycle back
> and forth over a half inch or so, taking repeated passes until
finish
> depth is reached?
>
> Or is there some type of cutting insert that can be used to take
> really deep (1/8" off radius) cuts with miniscule feed on a low
power
> machine? (ie, I want to cut 1/2" drill rod down to 1/4" at the
small
> end of my taper, using a 9" south bend as the basic platform)
>
> The goal of course? To improve over moving manually advancing the
> workpiece out of the chuck an inch at a time, cutting tiny stair
> steps, and smoothing with a file.
>
> Chris
>
> --
> Christopher C. Stratton, stratton@m...
> Instrument Maker, Horn Player & Engineer
> 22 Adrian Street, Somerville, MA 02143
> http://www.mdc.net/~stratton
> NEW PHONE NUMBER: (617) 628-1062 home, 253-2606 MIT