cutting spiral onto a rod

I need to cut a spiral onto a silver rod.
The sides of the cut can be at 90 degrees/and/or inclined. I envisage
this to be done by a lathe (milling machine?).
Diameter of rod could be 10-15mm,
spacing between edge of the next groove ca 3mm,
groove width & depth ca 2mm (ideally there should be some scope for
visual considerations).
Non electric system would be acceptable (or very slow speed lathe),
machine size should not be more than 1m, weight under 50kg.
Cost should not be more than $1000-1500, but this assumes that it can
be used for other applications, eg cutting tool steel etc.

I once owned a wood lathe (used it a couple of times only) & have used
a larger metal lathe under supervision for spinning.
Metal lathe users sites are so full of intalk that it is difficult for
a novice to decipher the essential info.
Any suggestions?

The machine you need is a screw cutting lathe. The essential difference
between this and a wood turning lathe, which you have used, is that the head
stock (the revolving bit that holds the work piece) is connected by a series
of gears to a threaded lead scew that pulls the top slide which in turn
holds the cutter along the work. The rate of travel is determined the
arrangement of the gears. With simple lathes you have to set up the gear
train yourself, but many, more sophisticated, have a gearbox.
A good machine tool supplier should be able to advise on the various lathes
available.
Thats the easy part. Learning to cut a thread(spiral) is another matter,
particularly one with straight sides. However once you have mastered it, it
is a relatively simple operation.
I would suggest that you find a book on amateur lathe work, they invariably
have a section on screw cutting. I taught myself with * The Amateurs Lathe*
by L.H. Sparey, First published in 1948 and still in print (at least in the
UK).
Of course, unless you are going to get a lot of use out of the machine, it
would be a lot cheaper to pay a machinist to cut the thread for you. Not so
satisfying tho'.
I hope this may be of some help.
Regards
Ben Smith


"norwick" wrote in message
...
I need to cut a spiral onto a silver rod.
The sides of the cut can be at 90 degrees/and/or inclined. I envisage
this to be done by a lathe (milling machine?).
Diameter of rod could be 10-15mm,
spacing between edge of the next groove ca 3mm,
groove width & depth ca 2mm (ideally there should be some scope for
visual considerations).
Non electric system would be acceptable (or very slow speed lathe),
machine size should not be more than 1m, weight under 50kg.
Cost should not be more than $1000-1500, but this assumes that it can
be used for other applications, eg cutting tool steel etc.

I once owned a wood lathe (used it a couple of times only) & have used
a larger metal lathe under supervision for spinning.
Metal lathe users sites are so full of intalk that it is difficult for
a novice to decipher the essential info.
Any suggestions?

Andrew, Abrasha, and Peter; let me tell you a story.

Back in the days when I was still "gainfully employed' I worked at a
"National Laboratory" in California in the Electronics Engineering
Department. One of the jobs I held there was to supervise a group of
people who's job was to "support" other Professional's computer systems.
This support included integrating computers into laboratory experiments
as well as office systems. In those days VMS and UNIX were big players
as well as Macs and early IBM-PCs, Windows was just emerging as I
retired.

One of the hardest jobs I had was to get each new support person to
understand that their job was to help the "customer" to get his job done
with the available computer system NOT to tell them that it would be
better done with what ever system the support person felt was the best.

The concept that there is almost nothing that can't be done with any
computer system (granting it may well be easier with one system) is not
touched on much in schools. All my people started with their own
personal favorite, to get them to understand that the other systems all
had a place and each had things that were better and worse than the
others was not something they were comfortable with at first.

While I could almost always get the idea across to my people, I found my
"customers" many times to be the most intolerant of the concept. To
stereotype some of the "customers" (always a dangerous thing to do) I
found the worst to be the programers, followed closely by physicist. The
most open to the concept were chemists. I guess you could make the
argument that the more you think you know about a computers system the
less tolerant you tend to be of other opinions ;).

My total experience with lathes is a one hour survey class in collage 45
years ago so I will not even pretend to have an opinion of the job under
discussion. But you might want to substitute "lathe" for "computer" the
above story and see if the analogy fits.

Richard Friesen wrote:


My total experience with lathes is a one hour survey class in collage 45
years ago so I will not even pretend to have an opinion of the job under
discussion. But you might want to substitute "lathe" for "computer" the
above story and see if the analogy fits.



Not even close! Small lathes cannot do what large lathes can do, and
vice versa. Besides, there really is no such thing as a generic lathe.
A watchmakers lathe can do certain jobs exceptionally well, but it
cannot machine the shaft for an ocean liner. And a 24" swing lathe,
cannot machine a ladies watch gear.

And the same is true for computers also, but I really do not want to get
into that discussion. It's been a long and tiring day, and I'm not up
for it.

So to make a long story short, I can do things on my PC, that I cannot
do on my Mac, and vice versa. In general you may be right, when it
comes to numbers crunching, data base computing, word processing, image
editing, some video editing etc. But for certain very specialized tasks
you are simply wrong. Sure, every computer given enough computing
power, has the same potential to perform any task, as long as the needed
software is available for any given OS.

If you retired when Windows was "just emerging", you haven't been around
for a while. It sounds like your knowledge of computing needs a little
polishing

Abrasha
http://www.abrasha.com

norwick wrote:
I need to cut a spiral onto a silver rod.
The sides of the cut can be at 90 degrees/and/or inclined. I envisage
this to be done by a lathe (milling machine?).
Diameter of rod could be 10-15mm,

If you want a single groove (like a screw), you can do this on any lathe with a
lead screw (a screw cutting lathe). However, this will only cut grooves with a
very small angle. (Close to 90 degrees to the length axis of the rod, just like
a machine screw). I can easily do this on my lathe for regular screw profiles.
If you want custom profiles, you need to make a special cutting tool, which
makes it more difficult.

If you need grooves cut at a 90 degree angle to the length axis of the rod, side
by side, then I can easily do this for you. You supply the rod, and a blue
print and I can do it for you.

If you want multiple grooves (2 or more), you need a screw cutting lathe with
the ability to cut multiple start threads. This requires more complicated
equipment, like a CNC lathe.

Another way that grooves are cut, but with angles more like the helical groove
in a twist drill (http://www.unionbutterfield.com/tech...menclature.asp),
is on a milling machine with the help of a universal dividing head
(http://www.hhip.com/products/product...uctID=800-5815). This is
called helix or spiral cutting. The table of the mill needs to have a motor
feed, and the dividing head needs to be coupled to the longitudinal feed (x
axis) of the mill, so that the rod to be grooved, rotates at a predetermined
number of degrees per set movement along the length axis of the rod. Sounds
more complicated than it is, but you do need the equipment and know how to use
it. I cannot do this with my mill and my dividing head.

In order to mill a helix there are three essential requirements:
1. The table must be set at the correct angle.
2. The index head must rotate the work in proper ratio to the table movement.
3. The work must be fed by the table forward to the cutter.

When these three conditions are met, the cutter will mill a helical groove whose
pitch or "steepness" depends upon the selected ratio between the index head
and table movement.

Here is a good article which shows rather sophisticated grooves. A CNC setup is
used here. http://www.mmsonline.com/articles/100204.html

Since silver is a pain in the ass to machine, you may be better off in getting
the rod, and find yourself a machinist who can do the grooving to your liking
for you. If you supply the rod, I'm willing to cut you a groove on my lathe if
that is what you want.

spacing between edge of the next groove ca 3mm,
groove width & depth ca 2mm


(ideally there should be some scope for
visual considerations).

What does that mean?

Non electric system would be acceptable (or very slow speed lathe),
machine size should not be more than 1m

What does that mean?


, weight under 50kg.

You want a machine, that can handle a silver rod with a diameter of 10-15 mm,
and that can be used for cutting steel, and should weigh under 50 kg?

Dream on! Especially if you mean with "1m" 1 meter. A metal cutting lathe of
one meter in length will never in your wildest dreams weigh less than 50 kg?
Hell the motor alone will most likely weigh around 15 to 20 kg.

Cost should not be more than $1000-1500, but this assumes that it can
be used for other applications, eg cutting tool steel etc.





I once owned a wood lathe (used it a couple of times only) & have used
a larger metal lathe under supervision for spinning.
Metal lathe users sites are so full of intalk that it is difficult for
a novice to decipher the essential info.
Any suggestions?

As I suggested before, find yourself a capable machinist to do the job for you.
You are in over your head, this is no job for a novice.

Abrasha
http://www.abrasha.com

"norwick" wrote in message
...
I need to cut a spiral onto a silver rod.
The sides of the cut can be at 90 degrees/and/or inclined. I envisage
this to be done by a lathe (milling machine?).
Diameter of rod could be 10-15mm,
spacing between edge of the next groove ca 3mm,
groove width & depth ca 2mm (ideally there should be some scope for
visual considerations).
Non electric system would be acceptable (or very slow speed lathe),
machine size should not be more than 1m, weight under 50kg.
Cost should not be more than $1000-1500, but this assumes that it can
be used for other applications, eg cutting tool steel etc.

[You could do this on a miniature CNC milling machine (like the Taig mills I
sell) equipped with a rotary table, chuck, and tailstock. You'd need to
program the toolpath to advance the tool along the X (long) axis while
rotating the A axis (the rotary table) so that the grooves were properly
spaced. A ball-end tool would give you a round-bottomed groove; a regular
endmill would give a flat-bottomed groove. The weight and size of this
machine would be about what you're asking for above, but the price would be
higher - about $3k, with the accessories you'd need. These machines can be
used for many other things, but for best results with tool steel anneal it
first, and use carbide cutters.]

I once owned a wood lathe (used it a couple of times only) & have used
a larger metal lathe under supervision for spinning.
Metal lathe users sites are so full of intalk that it is difficult for
a novice to decipher the essential info.
Any suggestions?

[You might be able to find a used metal lathe with thread-cutting abilities,
but they usually are limited by their gearing to producing standard threads;
you can't just pull numbers out of the air and expect the lathe to be able
to make threads to your arbitrary specifications. They are also generally
much larger and heavier than you specify, although there are some
intermediate-sized lathes made that have threading abilities(see
http://www.mini-lathe.com/ ).]

Andrew Werby
www.computersculpture.com

Andrew Werby wrote:
"norwick" wrote in message
...

I need to cut a spiral onto a silver rod.
The sides of the cut can be at 90 degrees/and/or inclined. I envisage
this to be done by a lathe (milling machine?).
Diameter of rod could be 10-15mm,
spacing between edge of the next groove ca 3mm,
groove width & depth ca 2mm (ideally there should be some scope for
visual considerations).
Non electric system would be acceptable (or very slow speed lathe),
machine size should not be more than 1m, weight under 50kg.
Cost should not be more than $1000-1500, but this assumes that it can
be used for other applications, eg cutting tool steel etc.


[You could do this on a miniature CNC milling machine (like the Taig mills I
sell) equipped with a rotary table, chuck, and tailstock. You'd need to
program the toolpath to advance the tool along the X (long) axis while
rotating the A axis (the rotary table) so that the grooves were properly
spaced. A ball-end tool would give you a round-bottomed groove; a regular
endmill would give a flat-bottomed groove. The weight and size of this
machine would be about what you're asking for above, but the price would be
higher - about $3k, with the accessories you'd need. These machines can be
used for many other things, but for best results with tool steel anneal it
first, and use carbide cutters.]

The motor that typically cames with the Taig does not have enough power to cut a
2 mm deep groove in a 15 mm diameter silver rod. The cutting force would stop
the spindle dead in it's track, or the rubber band (the drive belt that comes
with the Taig is no more than a big rubber band) would just slip.

Abrasha
http://www.abrasha.com

On Sun, 08 May 2005 17:37:37 -0700, in ¸õ Abrasha wrote:

The motor that typically cames with the Taig does not have enough power to cut a
2 mm deep groove in a 15 mm diameter silver rod. The cutting force would stop
the spindle dead in it's track, or the rubber band (the drive belt that comes
with the Taig is no more than a big rubber band) would just slip.

Abrasha
http://www.abrasha.com

Is that really an issue that would stop this? I don't have a Taig, but my sherline mill
can't be that different, nor is my little old unimat lathe. neither can do deep cuts in
a single rapid pass, but with a slow feed rate, and perhaps several passes as
successivly increased depth, it should be possible. I've cut things in silver deeper
and wider than that on the sherline, doing it that way. The low power machines, which
also suffer from less rigidity in the machine, simply mean you need to have a lot of
patience, doing the cuts slowly with multiple light cuts. At least, that was my
experience. Yes, it's slow enough to be quite annoying to anyone who's used full sized
machinery, but it can be done, nevertheless. I had one poject involving turning on the
Unimat, with a bracelet shape starting around 3 inches in diameter in platinum. That
was a bitch to cut too, and to keep the lathe from stalling took a tool bit with very
little radius at it's point (to make the cut dig into less metal at a time), and very
small amounts on each pass. But it eventually worked.

I'd guess the big problems would be simply generating the spiral desired without going
over budget on the machine, as well as the difficulties involved in cutting silver.
Back in graduate school, I cut pretty much this type of spiral in a slightly larger
brass rod without trouble. But it was a full size rockwell tool room lathe doing it.
It was quite capable of that sort of thread, essentially a thread with very low number
of threads per inch. Successive cuts were of course required then, too, to do it, not
so much because the tool didn't have power enough, but because a deeper cut put too much
stress on the workpiece, bending it. I'd guess one big problem with such a groove would
be too much power and too aggressive a cut, which might easily bend the silver too
easily.

I was also sorta wondering whether the need in this case might really require the
precision and accuracy of a machine cut groove. With care, one can also simply lay out
the spiral on the rod and do it with files, etc. Takes some skill and patience, to be
sure. But it's possible, I'd guess, to do a job that would look quite accurate, even if
a matching nut might not actually travel well in the "threads." One way to lay it out
fairly easily would be to wrap 2 mm drafting tape around the rod

And I'm wondering if such a thing might also be acceptably fabricated, rather than cut.
A pair (or three) square wires wrapped around the rod tightly and neatly, with one then
removed, leaves a rather uniform groove where it was. Solder the others down in place,
and you've got it. On a small scale, I've seen screws done this way on somewhat
primative things, such as screw on bracelet catches, or even the screws on the neck and
inside the cap of a small bottle. (wind two wires around a rod, unscrew one from the
other, solder one in the lid and the other on the rod, and you've a matching nut and
screw. Sloppier than machine cut, but can still function. Whether such an approach
would work, of course, depends on the application and design needs, but it pretty much
eliminates the need for any machinery beyond normal jewelry tools.

Also, if this is merely decorative, it might be possible to generate such a form by
twisting a straight bar with one or more longitudinal grooves. Difficult if not
impossible to get the pitch uniform from one end to the other, as it might tend to twist
tighter in the middle, or the like. And twisting generates it's own distortions of the
rod's surface and groove geometry. But again, for some uses, this might work.
Certainly in working iron, twisting square or otherwise non round rod generates such
decorative spirals. Iron, though, which is bent hot, is much easier to control, as the
heat determines where it bends the most, giving you more control than you'd have bending
cold silver.

Peter

Like Peter said, plus, if the piece were not too large, perhaps it could
be done in wax and then cast?

Carl


Peter W.. Rowe, wrote:
On Sun, 08 May 2005 17:37:37 -0700, in ¸õ Abrasha wrote:


The motor that typically cames with the Taig does not have enough power to cut a
2 mm deep groove in a 15 mm diameter silver rod. The cutting force would stop
the spindle dead in it's track, or the rubber band (the drive belt that comes
with the Taig is no more than a big rubber band) would just slip.

Abrasha
http://www.abrasha.com


Is that really an issue that would stop this? I don't have a Taig, but my sherline mill
can't be that different, nor is my little old unimat lathe. neither can do deep cuts in
a single rapid pass, but with a slow feed rate, and perhaps several passes as
successivly increased depth, it should be possible. I've cut things in silver deeper
and wider than that on the sherline, doing it that way. The low power machines, which
also suffer from less rigidity in the machine, simply mean you need to have a lot of
patience, doing the cuts slowly with multiple light cuts. At least, that was my
experience. Yes, it's slow enough to be quite annoying to anyone who's used full sized
machinery, but it can be done, nevertheless. I had one poject involving turning on the
Unimat, with a bracelet shape starting around 3 inches in diameter in platinum. That
was a bitch to cut too, and to keep the lathe from stalling took a tool bit with very
little radius at it's point (to make the cut dig into less metal at a time), and very
small amounts on each pass. But it eventually worked.

I'd guess the big problems would be simply generating the spiral desired without going
over budget on the machine, as well as the difficulties involved in cutting silver.
Back in graduate school, I cut pretty much this type of spiral in a slightly larger
brass rod without trouble. But it was a full size rockwell tool room lathe doing it.
It was quite capable of that sort of thread, essentially a thread with very low number
of threads per inch. Successive cuts were of course required then, too, to do it, not
so much because the tool didn't have power enough, but because a deeper cut put too much
stress on the workpiece, bending it. I'd guess one big problem with such a groove would
be too much power and too aggressive a cut, which might easily bend the silver too
easily.

I was also sorta wondering whether the need in this case might really require the
precision and accuracy of a machine cut groove. With care, one can also simply lay out
the spiral on the rod and do it with files, etc. Takes some skill and patience, to be
sure. But it's possible, I'd guess, to do a job that would look quite accurate, even if
a matching nut might not actually travel well in the "threads." One way to lay it out
fairly easily would be to wrap 2 mm drafting tape around the rod

And I'm wondering if such a thing might also be acceptably fabricated, rather than cut.
A pair (or three) square wires wrapped around the rod tightly and neatly, with one then
removed, leaves a rather uniform groove where it was. Solder the others down in place,
and you've got it. On a small scale, I've seen screws done this way on somewhat
primative things, such as screw on bracelet catches, or even the screws on the neck and
inside the cap of a small bottle. (wind two wires around a rod, unscrew one from the
other, solder one in the lid and the other on the rod, and you've a matching nut and
screw. Sloppier than machine cut, but can still function. Whether such an approach
would work, of course, depends on the application and design needs, but it pretty much
eliminates the need for any machinery beyond normal jewelry tools.

Also, if this is merely decorative, it might be possible to generate such a form by
twisting a straight bar with one or more longitudinal grooves. Difficult if not
impossible to get the pitch uniform from one end to the other, as it might tend to twist
tighter in the middle, or the like. And twisting generates it's own distortions of the
rod's surface and groove geometry. But again, for some uses, this might work.
Certainly in working iron, twisting square or otherwise non round rod generates such
decorative spirals. Iron, though, which is bent hot, is much easier to control, as the
heat determines where it bends the most, giving you more control than you'd have bending
cold silver.

Peter


--
to reply, change ( .not) to ( .net)

Carl 1 Lucky Texan wrote:
Like Peter said, plus, if the piece were not too large, perhaps it could
be done in wax and then cast?

Carl



To cut a helix in wax you would need the exact same setup as for metal.

Abrasha
http://www.abrasha.com