"Jim Wilkins" wrote in message
...
On Nov 13, 9:07 pm, "Michael Koblic" wrote:
"Jim Wilkins" wrote in message
[...]

Now here is a question: For a job like that could one get away doing say a
9" plate at 300 rpm if the feed was *really* slow? One of the reason I am
going through this rigmarole is to get the speeds down to 40-80 which the
books tell me would be more appropriate.
Michael Koblic,

That depends on the plate and tool bit materials. The speed limit is
where the tool point heats up enough to soften and you probably won't
see it. For example you can soften and dull the teeth of a cheap
hacksaw blade by sawing tool steel too quickly. 700 FPM at the outer
edge should be OK for aluminum but it's -way- too fast for steel, I
run 80 - 100 FPM, and 50 or less for cheap half-fast-steel Enco end
mills and lathe bits.

***That's what I thought...BTW how does carbide behave in this situation? I
bought a boxful of carbide inserts which were a part of a lot of small
metalworking items in an auction as well as some holders to go with them.

Look at the lathe in Fig 92 of Holtzapffel. The drive engages the
outer rim of the faceplate rather than a pulley on the spindle, so one
part does double duty. A plastic kiddy bicycle wheel might work. The
reversed tapered pulleys, which could be wooden, let you change the
speed through a 7:1 range while the lathe is running so you could run
40 RPM at the edge and 280 in the center. The lever that slides the
cone pulley belt, called a Shipper, could be connected to the slide
rest with a cord to make the speed change automatic

***I did and was suitably impressed. In fact a friction drive of some kind
was something I did consider (and have not totally rejected). At this point
I am mind of aiming for a three-story type of arrangement: Two pillow blocks
with a 9" pully in between, belt through a slot down to the middle level
where additional transmission (yet to be determined) will change the speeds
and a belt from there down to the basement with a motor on a hinge plate
driving it all. But I am not married to it.

I am independently pursuing another arrangement partly based on some of the
ideas you have imparted. But all is on hold as I have been playing withe
mill for the last three days. I have also three dials to finish for the
Christmas shopping rush and a router table (I seem to do more woodwork than
metalwork these days and if I am going to be making wooden pulleys ti will
be even more. BTW, how do you attach the wooden pulleys to the shafts? I was
thinking a split collar with a hose clamp...)

The slide rest is fastened to simple non-precise ways and aligned
parallel or perpendicular to the spindle axis with a test bar or by
measuring the cut. You could try an X-Y table or vise.

***I knew I should have bought that sliding cross vise in the auction the
other day...It has been bugging me ever since.

These are some of the ideas I hoped you would get from the book. The
hard part is hiring enough Egyptians to pile up all those stone blocks
for the base. (It's a 25' x 40' lathe by James Nasmyth)

***The book is a gold mine - thanks for recommending it. Just the
work-holding ideas are worth the price.

--
Michael Koblic,
Campbell River, BC