Tim, you can check the rigidity of the compound/top slide to see if it is
firmly supporting a cutoff/parting/grooving tool with overhang, particularly
since the compound is located near the edge of the cross slide on a Smithy.

By placing a length of stock or a bar-shaped tool about 12 inches long in
the toolholder (or turret), and applying light to moderate vertical finger
pressure at the end of the bar, any movement that is seen in the compound
would be an indication that the cutting tool has vertical movement onder the
load of cutting.
Besides the cutting tool being able to dip down while cutting, any sideways
twist will very likely break a small cutting tool of that size.

If you're compound is set parallel to the spindle axis, you may want to try
resetting it to be perpendicular to the spindle axis, or somewhere
in-between.

I realize that supporting such a short/small part with the tailstock center
on a Smithy is probably not possible. Attempting to use the extension for
the tailstock ram will probably not be worthwhile, as the overhang is too
great for the area of the base of the tailstock.

I agree with the suggestions of placing the cylinder on an expanding arbor,
this would be a great improvement over trying to chuck a hollow part.

If you have a big endmill holder (and a drawbar) that fits the spindle taper
MT4, it should be a good substitute for using a chuck.
By turning a snug-fitting stem to put in the big endmill holder, a stub (the
diameter that would hold your cylinder) could be turned for it to mount on.
If you wanted to go further, you could drill the stub, tap for a 1/8" pipe
plug or set screw, then slit the stub so it would expand inside your
cylindrical part.
Otherwise an end screw and a washer would probably suffice (with the motor
running in the forward direction).

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Tim Wescott" wrote in message
...
On Sat, 27 Dec 2008 08:55:14 +0000, Harold and Susan Vordos wrote:

That is likely a function of surface speed. The tool should have held up
for the amount of cutting involved. Try slowing down ever so slightly.
If the chips came off anything but a pale yellow or silver metal color,
you ran too fast.

As you increase rake, the tool will tend to peel the metal instead of
push it off. That lowers cutting pressure and often results in a cooler
cut----although with the reduced mass at the point of cut, the result of
the angle of rake, the tool may heat just as quickly as it did
previously. Pressure will be lower, however, and that's a good thing.

Cooling is important, but not nearly as important as lubrication. It's
virtually impossible to part dry---although a few metals will cooperate.
Leaded steels and brass tend to part dry fairly well, as does 2024
aluminum, but you're never sorry for adding lubrication. If it doesn't
do anything else, it helps chip evacuation, although there's far more
involved. You limit or eliminate chip welding, and cut cutting pressure
in ways that are hard to believe. You need not flood the cut----an
acid brush (don't use a paint brush---it doesn't hold a supply of oil
the way an acid brush does) held in the groove while cutting will make a
remarkable improvement, plus the reduced friction will yield less heat.
Overall, you'll see an improvement you can't believe. Give it a go.
You'll be pleasantly surprised. If you don't have any of the 1,1,1,
trichloroethane, try sulfur based cutting oil. It stinks, but it does a
decent job.

One more consideration. The material you're using can make a huge
difference. If you're using mild steel (C1018 up through any of the 1020
materials, hot or cold rolled), you can expect grief. You might
consider making the cylinder out of Stressproof (1144). It machines
beautifully, especially with HSS. It also has great properties.

Be certain to have relief properly ground.

It would have been interesting to hear about the lathe you're using.
Did you make mention and I missed it?

Small machines are not the best scenario for parting, although with a
narrow tool you should achieve excellent results. If you find you're
having trouble, use a narrower tool, plunge the centerline of each
groove, then, using a long travel indicator, step over and face each
side. With a sharp tool you should be able to do so without problems,
assuming the fins are reasonably thick.

How about a report on the project when you're finished? I'd be
interested in hearing the outcome. Sounds like a good one to pursue.

Harold

Sorry -- it's a Smithy "3" in one (actually 2 + excuse in one, but the
excuse is the milling section; the lathe seems to be pretty good). Other
than the compound, which seems to have some taper in the dovetail, I can
get good control of the rigidity by snugging down the jib screws.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html