On 2009-07-06, Michael Koblic wrote:

"DoN. Nichols" wrote in message
...

[...]

I cannot imagine that a lot of torque was required of Singer sewing
machines. What hapens to torque at the lowest speeds?

Enough to handle sewing through leather to make thumbstraps for
English system concertinas. (Granted, you are part of the feedback,
adjusting the pressure as needed to maintain the speed which you can
work with.

That cleared that up...:-)

A person for feedback can help a lot.

[ ... ]

I got one of them drills, too. But again, what happens to the torque at
the
low speed if using a rheostat? On mine there is a slow start feature
which I
take to be nothing more than a rheostat. I can stop the chuck by hand at
the
low speed.

At absolutely the lowest speed, yes it is easy to stall. If you
have a foot pedal, you are adjusting the pressure to maintain the speed
you want, so it is no problem.

It is standing on one leg while turning I am a bit concerned about :-)

You put it on a lower surface, and sit down so your foot is more
comfortable. :-)

And remember that you are also *first* using the maximum *belt*
speed reduction to keep the motor's speed up a bit.

The whole thing (Singer, foot pedal etc.) has a certain attraction to it. A
sort of Kalashnikov feedback. When the time comes I shall explore this
concept.

O.K.

I got a 13.6V 20A power supply - that's 1/3HP.

Just 13.6V or variable voltage all the way down to zero? If the
latter, you can use it with a 12V drill motor to get variable speed.

It is fixed but making a solid state voltage controller is no problem.

Given the current involved, you probably want to make it a
switching regulator instead of a linear one to reduce the power lost as
heat -- and the size of the heat sinks needed.

Others have put me off doing that because of the feedback issues discussed
earlier.

The larger the machine the more feedback you need -- or the
stiffer a motor to start with. In this case, you are going through
quite a bit of speed reduction, so you may be surprised at what the
motor can handle -- especially if you go with a timing belt and pulleys
for the last stage.

[ ... ]

This would mean turning the spindle shaft down to at least 3/8". I do not
think this is possible. AFAIK the spindle is 5/8" with a 5/16" ID. Some
of
the plain bore pulleys have large enough bores but maximum of 24 teeth
or
so.

Look at the hub diameter in the pulley data. You should be able
to bore it out to fit the existing spindle. I would *never* consider
turning down the spindle to fit the pulley -- always modify the least
expensive and easiest to replace part.

I somehow asumed that it was not a done thing to bore out the *finished*
pulleys as they make the plain pulleys that *are* meant to be bored to
specs.
Looking at the 57105K3

You mean 57105K33? That is acetal with an aluminum hub, which
would be too weak to handle that kind of treatment -- or the kind of
loads involved. Steel would be better (and more expensive, of course.
:-) Perhaps Acetal for the smaller end pulley, and steel for the larger
end on the lathe's spindle.

the hub is 7/8" which after boring to 5/8" ID would
leave walls 1/8" thick. You think that is all right? The 6495K733 is steel
and has a 1.5" hub.

Put more information about the pulleys. I'm going to have to go
back to McMaster Carr's web site and print out that page.

Anyway -- even if pinned, that one is acetal on aluminum. No, go
for the steel -- you get more hub to bore and to hold the setscrews.

The other issue I thought was that using the exisiting Taig step pulley on
the countershaft together with, say, 6495K713, would lead to an ID
mismatch which could not be corrected by boring alone (this one has a hub of
only 1/2"). Some sort of bushing for the Taig pulley perhaps?

Or -- start out with a shaft which fits the Taig pulley, and
turn one end down to accept the smaller pulley.

And you won't want to be stepping up speed to the spindle, so
the larger pulley will be on the spindle, thus with the largest hub
diameter too.

Or -- go for the taper-lock type hubs where you can change hubs
to fit the shaft once you have the right pulley.

Presumably you are referring to something like this: 6495K222. The cost is
getting up there.

No -- those are cylindrical bores. Look at "57095K11" -- and in
particular "57095K112" which is for a 5/8" shaft. But the problem is
one of finding the right timing pulleys to fit. These are for larger
belts ('H' (heavy) series, not 'L' or 'XL'.)

And I would not worry about boring out the larger pulley to fit.
You'll need means for measuring your bore to know when you are at the
right size -- which probably means making up a sample shaft with a step
0.010" too small, one 0.005" too small, one the right size, and one
about 0.002" too large. Stop before the too large will fit in. And be
sure to remove the setscrews before you start boring. Hold it by the
hub in the 4-jaw, and take a lot of time tuning it to on center before
you start boring.

[ ... ]

12" swing,
Increased rigidity,
The Holy Grail...

How about 18" swing or larger? :-) It all depends on what you
want to make. In this case, how large a dial do you want for your
sundials? You *could* use a gap-bed lathe for that -- but there can be
problems getting the gap insert back in precisely enough so it does not
affect accuracy of turning close to the headstock.

I do know that I occasionally find projects which would go
better with a larger lathe -- but I don't really have room for one.

Oh, about 12 feet I guess:

http://www.milesfaster.co.uk/gallery...k/sun-dial.htm

Hmm ... I'll bet that was not made on a lathe, but rather formed
up from stainless steel, and welded into shape. If it were solid enough
to turn on a lathe, the supports probably would not hold it. :-)

But one has to walk before one can run. Also one must consider the size of
the etching bath, how many gallon bottles of Ferric Chloride one would need,

The markings on that one were welded onto the stainless steel
surface, not etched into them. As the scale goes up, the production
means must change.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---