Re: [CAD_CAM_EDM_DRO] Re: Swiss turning conversion

Doug, thanks for the insightfull comments

> 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.

I see CNC primarily as a tool for design flexibility, for turning
calculated curves on my computer into steel tooling (tapered mandrels
for drawing musical instrument parts), rather than for mass
production. I'm sure the necessity of carbide bushings is true for
production - in my case I'm making limited quantities of tooling
rather than finished parts, so having a bushing that wears out after a
couple hours of use is not a problem. So I guess I am wondering if I
might do something with bearing bronze or even babbit - basically,
imitate classic spindle bearing technology of an earlier era. (hmm,
babbit or moglice cast in place around a sample of the feedstock that
has been coated with a thin release?) I could probably even make it
adjustable via shims or slotting.

Alternatively, anyone know what a 1/2" bore non-rotating guide bushing
goes for? and what it would take to hold it?

> 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.

Would drill rod be good enough as supplied? I believe it is usually
centerless ground. The cost of machining my parts dwarfs the material
cost, so I'm willing to pay a premium for good stock.

> 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.

Tempting, if I had the space for another machine but alas I don't even
have room for my current equipment. Arguably, I should farm the
machining of these tools out, but I would really love the freedom to
be able to make one myself if a whim to try a slightly different
design strikes on a Sunday afternoon.

Although the mention of cams does bring up a good point. What is the
best zero-backlash actuator when one only needs say 1" of travel? Is
it still a ball screw and double nut with preload? What about an acme
screw working against a large spring... or a cast moglice nut? Or can
one drive the cross slide from some sort of cam?

Chris

--
Christopher C. Stratton, stratton@...
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