On 2008-12-21, Michael Koblic wrote:
DoN. Nichols wrote:
[ ... ]
Hmm ... I thought that it ran slower than that with the
multi-step pulley which came with mine. I do know that the top speed
is quite scary. :-)
But a different AC motor -- at half the speed -- should do fine.
And this is where the total cost begins to equal or exceed the mini :-)
Well ... the motor on mine is an inexpensive motor, and you
should be able to pick up a used motor with half the speed for not too
much. The main thing is that you want one with the same diameter shaft,
since you can't bore the motor pulley out to a larger size with the
lathe without a motor. :-)
There is a limit as to how much horsepower you can pump through
that ultra-skinny belt, so there is no point in going for expensive
motors.
Let's see -- you're in Canada, aren't you? In that case, you
may have 50 Hz power instead of the 60 Hz in the USA. That means that
the motor speeds will drop by a similar ratio.
Now -- the fastest induction motor on 60 Hz will run somewhat
slower than 3600 RPM (probably 3500 or 3550 depending on slip) from 60
Hz. That same motor would be 3000 (2900 or 2950) on 50 Hz. For
convenience let's work with the synchronous speed, even though it will
run somewhat slower. Anyway this is for a 2-pole motor.
A 4-pole motor would be 1500 RPM, and a 6-pole motor would be
1000 RPM. I've seen 900 RPM on 60 Hz (presumably 8-pole), which would
be 750 RPM on 50 Hz.
Now -- that would be with the middle set of steps on the pulleys
(equal diameter in and out). I would think that the pulley could get
the spindle down to 200 RPM or so with that motor. (Maybe I should
actually measure the speeds on my lathe?
You produced a shoulder as well as a thread with hand tools?
I cheated. The shoulder was there already.
:-)
The problem with a die is that it is easy to start one out of
line and then very difficult to get the thread back in line.
Tell me about it! I routinely chuck my gnomons (even those without a
shoulder) in my drill press, hold the die in the drill press vise and thread
that way. So far so good...
O.K. That helps -- as does a sliding die holder on the lathe.
But for the larger diameters, you would have to start the die under
power, and then switch out of the lathe to manual operations.
And -- if the diameter is an unusual one, dies to cut that
thread can be quite expensive.
But if you have a lathe can you not turn the diameter to something usual?
If something usual will indeed be strong enough. There are
times when you want a larger diameter for strength, but an uncommonly
fine thread to engage in fairly thin material for the female thread.
I
did this in the drill press with a file. Fortunately it only needed a small
amount to take off.
O.K. Beware of the side pressure of the file popping the drill
press's chuck off of the spindle and leaving it (and your workpiece)
skittering around the room.
Yes -- a die can be quicker -- if you can grip the workpiece
firmly enough. But lathe cut threads can be a nicer appearance than
most die cut threads.
Gripping strongly has not been a problem. Chewing up the piece by doing so
was.
That is where a collet helps -- assuming a cylindrical surface
for the collet to grip. Tapers make life more difficult.
Right now it is 3.5 degrees C in my "workshop" and I do not really want to
be there :-).
I can understand that. About 38.2 D -- kind of nippy, though
better than -40. :-)
I was supposed to get my woodworking stuff in order (I seem to
be doing more of that than I thought I would have to) which included making
a router table and extending the work bench. I made the router table before
the weather hit. I got as far as the planning stage with the bench. Still,
an opportunity to do some homework. I have also developed a line of clamp
knobs from bottle tops, 1/4"-20 bolts and epoxy. They are ugly but cheap and
can be made in the warmth of the heated house.
Warmth is *really* needed if you want the epoxy to cure in a
semi-reasonable time. :-)
I wonder what there is in the gagage that is going to freeze...
And 3.5 C? Nothing likely. But get colder and ...
Anti-freeze*? :-) Glues? The epoxy itself? Oil should have no
problems, though grease can get thick enough to do no lubrication for a
while. :-)
Good Luck,
DoN.
* Yes -- anti-freeze will freeze at a higher temperature than the
optimum mix of anti-freeze and water.
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