On Fri, 11 May 2007 01:30:31 GMT, "CW" wrote:


"Prometheus" wrote in message
.. .
On Wed, 9 May 2007 09:49:21 -0700, "Charles Friedman"
wrote:

The first is that most wood lathes (at least, the ones I see) are a
gap-bed style. To fit and use a compound slide, you sort of need ways
that are made of a solid piece. A person could always mount ways on
the gap bed, but you'd lose some swing, and it'd be tough to align
properly (IMO.)

Many, if not most, medium (14" to 24") engine lathes are gap bed.

That's likely true- I haven't seriously been shopping for them, and
most of the lathes I've used in metal turning have been CNC, with no
ways at all to speak of. What I'm most familiar with is a flat ways
with no gap.

The second is that a belt drive really isn't good for metal turning.

Most all engine lathes are belt drive. It wasn't until the CNC that direct
drive became common and is still only used on them. Manual machines use
belts. I've made hundreds of parts on lathes driven by flat leather belts,
more with the more modern rubber belt drive.

Huh- learn something new every day, I guess! I was repeating
Gingery's take on it, as I am about halfway done with making my lathe
off his plans. My goofing around with *real* manual metal lathes has
never included removing the cover over the drive components, so I had
assumed that Gingery's take was based on some fundimental truth I
wasn't previously aware of.

Kind of a relief to hear you say that, actually- I was a little
worried that the homegrown lathe wouldn't be much use until I got all
the gears on. I can afford steel and tooling bits- but aluminum and
brass for turning (especially during a fairly extensive learning and
re-learning process I'm likely to have to go through) are a little out
of my price range right now.

It's really a pretty sorry situation right now- I used to be pretty
good with manual machines, but it's been all CNC for a while now, and
I feel like a retarded kid every time I start making something on old
equipment. It took about 40 hours to get back up to speed on the knee
mill at work, and I had thought I could just jump right on it and go.
At least I'm turning out nice parts on it now- but I figure the engine
lathe is likely to be a similar situation when I get it running.

You want back gears if you're going to be turning slow, so that all
the torque isn't lost, and you need them if you expect to be able to
cut threads.

That's true. The gearing is between the spindle and feed rod/leadscrew. The
spindle is still turned by belts. If the spindle changes speed for any
reason, the feed rod or lead screw changes with it as they are geared
together. I have changed spindle speeds in the middle of a threading
operation with no loss of accuracy.

On another note- I give up. On some other thread quite a while back,
you had said that you could make a wheel on a knee mill that was as
good as one turned on a lathe without a rotary vise. I've been
racking my brain on and off over that one, and have come up with
nothing. Any chance you can give me a hint of how that is done? I
don't really need to do it, I just want to know!