"Ignoramus13376" wrote in message
...
On 2013-06-06, Existential Angst wrote:
"rangerssuck" wrote in message
...
On Tuesday, June 4, 2013 11:21:20 PM UTC-4, DoN. Nichols wrote:

You'll probably also get a rather poor finish at such low speeds
with such small workpieces.

OK, I understand why 500rpm is too low to cut properly on small
diameters,
but is it possible to increase the speed of this particular lathe? Is
there something about the drive or bearings that makes it impossible?

Proly could just change the motor speed (assuming the motor is not
already
3600 rpm), and/or the drive pulleys. I'm sure the bearings could handle
it,
altho it is generally true that the faster the rpm, the faster the wear.
Many lathes come with two-speed motors.

This lathe is 70 year old by design and age.

Can you increase the "motor speed" of a 70 year old grandfaher? What will
happen to the grandpa in the long run? we all know

I already conceded that wear is proportional to stress, rpm. 80 mph is more
wear/tear on a vehicle than 50 mph....
And????

You can give grandpa a heart transplant, and swap out the motor, for a
higher rpm motor. Or the pulleys.
Not saying you should do it, just saying it can be done, and you'd have yer
cake and be able to eat it too.
You've already stated that you refuse to retain two lathes. This would be a
good solution, if you really like this lathe other than the rpm.

If you were doing lots of 1,000+ rpm work, I'd say keep both lathes, as
others have suggested.
If not, you have to make a choice. Swapping the motor, pulleys is just
another option.
--
EA



i

On 2013-06-06, Existential Angst wrote:
"rangerssuck" wrote in message
...
On Tuesday, June 4, 2013 11:21:20 PM UTC-4, DoN. Nichols wrote:

You'll probably also get a rather poor finish at such low speeds
with such small workpieces.

OK, I understand why 500rpm is too low to cut properly on small diameters,
but is it possible to increase the speed of this particular lathe? Is
there something about the drive or bearings that makes it impossible?

Proly could just change the motor speed (assuming the motor is not already
3600 rpm), and/or the drive pulleys. I'm sure the bearings could handle it,
altho it is generally true that the faster the rpm, the faster the wear.
Many lathes come with two-speed motors.

Note that there is a maximum speed rating for each chuck -- and
the larger the chuck, the lower that speed rating. At higher speeds,
centrifugal stresses can cause the chuck to turn into a collection of
Shrapnel flying in different directions.

Now -- if you have collets for the large lathe, you could
probably get away with speeding it up. But then you need to worry about
other workers not knowing about the speed limitations of the chucks,
and/or being too lazy to pull the chuck off and replace it with a much
smaller one, or a collet prior to running some high-speed cutting.

Maybe a smaller motor and spindle held in the big chuck could
give you high speed when you need it.

Enjoy,
DoN.

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Don' please elaborate on "smaller motor and spindle held in big chuck". Sounds interesting.
Ivan Vegvary.

On 2013-06-07, Ivan Vegvary wrote:

Don' please elaborate on "smaller motor and spindle held in big chuck". Sounds interesting.
Ivan Vegvary.

Well ... lots of possible ways to do it. One would be a spindle
which passes though the main spindle and is held in the large chuck.
That one would be driven by an outboard motor which couples in through
the back of the spindle.

Another would be a spindle (and bearings) held in the big chuck
with a pulley on the workpiece side of the big chuck, and with a belt
going to a motor behind the bed -- and likely behind the headstock as
well.

In any case, you want to lock the spindle by engaging both back
gears and direct drive (unless this is purely gears inside the
headstock, in which case I would look for some form of spindle lock on
the headstock. And interlock it so nobody can power up the main
spindle, because that would beat the motor and the bed to death.

Without seeing the lathe, I don't know what would work best --
and it would also be dependent on what parts you could find. For a
really small setup, something like the spindle cartridge from a Unimat
SL-1000 (goes for insane prices these days, because they are collector's
items). For that, you would have to make a drive tube which threads
onto the outside end of the Unmat spindle cartridge in place of the
pulley and nut, and extends outside the far end of the main spindle.
Install a bearing on the outboard end of the drive tube which is a nice
fit inside the outboard end of the big spindle. This would then let you
use some small three and four jaw chucks, and with creative work and the
WW (watchmaker's) spindle for the Unimat, even really tiny collets.

I wonder whether you could take the spindle cartridge out of a
Taig lathe -- a little bigger than a Unimat SL-1000, and a lot more
affordable, since it hasn't become a "Collector's Item".

What you would lose would be any existing power feeds on the
lathe, and have to come up with some other way to do those, too.

Maybe mount a small cross-slide and compound on the big one, to
give you finer feeds.

Just some speculation. :-)

Enjoy,
DoN.

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