Not all sizes and
wall thicknesses of tube come seamless from a factory or refiner. Especially
when working in gold it is not cost effective or timely to order in a specific
tube size, material, or wall thickness. There are many times when you need
a piece of tubing, you don't have it, and you can't wait a day or so to
order it in or run across town and buy it. In general, it is possible to
make the length of tubing you require for an object in about fifteen minutes.
When compared with the time required to go across town to buy the tube,
or order it in, as well as paying more than the cost of the material for
the privilege of buying ready-made tubing, it is clear that making your
own is a cost-effective, rapid way of obtaining it. When you need very thick
walls it is particularly important to be able to make your own tubing.
To make tubing you have to define your needs: what wall thickness what
outside diameter what inside diameter what material type you need. Did
you plan for the material and structural requirements when in use in your
Some goldsmiths keep a few sizes (generally larger ones) of gold tube
in the shop and then rapidly draw it down to the sizes they need when
a job comes up. This saves having to buy a large selection of sizes to
have on hand.
You will also need some tools for drawing. Drawplates in larger sizes
are essential. They should be steel and are rather expensive. For very
occasional use a wooden draw plate, or brass, delrin or nylon may be used.
Best is a proper steel one. While one can draw tubing by hand, in the
larger sizes and thicker walls it is really pleasant to have a draw bench.
Because, for all intents and purposes, the wall thickness of a tube
does not change during drawing, unless you're down in the very small sizes,
you start out with the wall thickness on you want to end up with. Only
when a tube has been drawn very small (for example, with an inside diameter
of less than 0.5 mm) does the wall thickness appear to change and begin
to thicken while drawing the tube.
Let us assume then that I wanted a wall thickness of one millimeter
on a tube with an outside diameter of 3 mm. I would first determine the
circumference of a 3 mm diameter tube. C (circumference) =P x D (diameter)
so we would multiply 3.14 times 3 to obtain 9.42 mm (P=pi=3.14 more or
less). This represents the minimum width of the blank required to make
the tube. The sheet used would be 1 mm thick.
C = P x D
C = 3.14 x 3
C = 9.42 mm width of blank.
In order to have a nice round tube and get a reasonable length with
a tightly drawn seam we start bigger than this so I might choose a blank
width of 12 mm or more. We have to plan for some material for a tang to
draw the tube with and so we will make the length of our blank at least
as long as the final desired length of the tube, plus the tang length
(if not longer). The end of the tube to be drawn is cut at a broad taper,
and the sides of the strip that we are going to be using to make the tube
It is pretty much the same amount of work to draw a short tube as a
long tube so you might as well make it quite a bit longer than you need,
so that when you draw the tube, you get more than you need, and so develop
a stockpile of tubing in various sizes and wall thickness in the process
of doing the work you were doing anyway. Often with tube making it is
worthwhile making a much longer tube than you need, and cutting off 2
inches. (5 cm) from the back every few holes as you draw it down. In this
way you end up with a great selection of tubing in graduated sizes. This
is particularly worthwhile with thick-walled tubing. An important principle:
always make more than you need-it is the same amount of work and you will
need some more tubing at a later date.
actual tube width we will start with
Sometimes, particularly with precious metals such as gold, one doesn't
feel like utilizing material for the tang, which will just end up as scrap,
so one can take a small piece of brass or even silver wire, and solder
it onto the end of the rectangular blank from which one makes the tube.
This will serve as a tang to draw with. For gold and similar costly materials
it can be a good idea to avoid some wastage by soldering on a wire of
a less expensive material instead of making a taper to draw the tube with.
When all is said and done, and the tube is finished, you unsolder that
small wire tang, and this way you didn't have to use up some of your gold
in a tang for drawing. If I do this I will taper roll the wire and tube
beginning to blend them into each other. Roll the end in slightly, back
it out and put it in again at 90o to the first direction, then go to the
next smallest hole and do the same thing only not as far in on the wire.
Continue in this way until you have a smooth tapered point.
Tubing, too, can be step rolled to get a taper on the end for drawing
it. You make the tube without any taper to the blank. Then you taper the
end with the wire rolling mill as described above. This gives you a solid
tang to draw with but the tang material becomes scrap at the end of drawing.
One can solder the tapered end for more strength while drawing.
I like to shape my tubing blanks into wood-that is, that I will take
a stump and I will use a forging peen, or the peen of my bench hammer,
and make a groove or dent into the endgrain of the wood, then shape the
tube into that to obtain a half round cross-section. I don't like to use
commercial tube-shaping swage blocks, which are steel blocks with half
round grooves in them, because I find that they tend to damage the sheet
metal of the tube quite a bit during the making. So, again, for me, it's
a wooden shape of some type that I form into. The blank is tapped into
the groove using the hammer, and rolled sideways while tapping onto it,
back and forth, so that the sides of the groove form the metal around
the hammer at the same time as the hammer is pushing the tubing blank
into the groove. First of all, we shape it into a "U"-shaped cross-section.
It is at this point that we can "true up" the two sides of the blank they
are now in the same plane and so we can file down the length of the blank,
evening up both of them simultaneously.
When you hammer and shape, don't make small dents or nicks you want
the shaping to be as smooth and un-bumpy as possible. After you have reached
the "U"-shaped position, you then begin hammering at about forty-five
degrees to the edge of the trough. You hammer gently while rolling the
blank back and forth until the cross-section of the tube becomes somewhat
pear-shaped, perhaps even a little bit teardrop-shaped. At this point,
we can tap it so that it is more or less round, and we can begin drawing
it through the drawplate.
It's perfectly possible to draw tubes under about five or six millimeters
in diameter by hand, but for over this size, or for tubes with a very
heavy wall thickness, such as a two millimeter wall (which is something
that one does sometimes) it is preferable to use a draw bench of some
type. We draw the tube through the drawplate until it is smooth and round.
At this point, I stop, and I will inject a watery flux solution inside
the tube until I see flux run out the bottom of the tube to make sure
that the interior seam is protected, then I flux the outside of the tube,
and anneal the entire thing. This releases any stresses built into it
from making it, and the gap, the seam, will open slightly. Rinse it off
with hot water to dissolve and remove flux residues-do not pickle it (we
don't want a pickled finish inside our seam because solder does not like
to flow onto pickled surfaces)-and then draw it through the last hole
that it went through in the drawplate, just to tighten it up. At this
point, the seam is tight-as tight as it's going to get-and you have just
removed all stresses by doing the annealing procedure. Then re-flux the
interior of the tube with a syringe as before, flux the outside as well
and solder it, if it's going to be a soldered tube. When drawing it down
further, to find the correct hole to draw it through next, take the back
of the tube and try and push it into the hole you think is right. When
the tube will not go in then the correct hole to use is the next one down,
the next smallest hole.
After soldering, any spilled solder is cleaned up, the tubing is pickled,
and then it is drawn further until you have reached the outside diameter
that you require. One of the things you have to watch out for in making
your own tubing is having overlaps of the seam, so when you're closing
it up with the hammer, before you even begin to draw, make sure that everything
is nice, clean, that the seam consists of even butt joints, and that you
have no overlaps occurring.
Another thing that can sometimes occur, is that during drawing the tubing
twists, so that your seam is not a straight line down the length of the
tube, but in fact twists or spirals around the tube, which is not a happy
situation. The way that you fix this is, while you are drawing it, you
place a jackknife, held carefully, clamped securely with pliers, in front
of the drawplate, and insert the jackknife into the seam of the tube at
the same time as the tube is drawn. This will automatically straighten
up the seam into a single, even, parallel line.
A warning: if you press down too far with the jackknife, you'll end
up with two half-tubes-I've been there, done that. For much hinge-making,
we don't, in fact, use soldered tubes, because, if you do, then when you
install the tube into your hinge, you don't know where the seam is, and
usually it's in a nice, open, wrong position, and the solder flows out
of it during the solder job, and then you're left with a visible gap or
a seam. So, if we're going to be using tubing for hinges, often we do
not solder the seam until we're actually installing the hinge knuckle
in place, and during that installation, the seam is then soldered closed
at the same time as the tube knuckle is soldered down, combining both
steps and ensuring that the tube seam faces inwards and so is hidden on
the finished piece.
Drawing thick walled tubing
Thick-walled tubing has special applications for hinge-making, and there
are some silversmiths' hinges that only work if they're constructed with
very thick-walled tubing. Certain bracelet hinges, too, require that the
walls be quite thick and strong in order to have the bracelet function,
or the catch function, as will be seen in the discussion of hinge-based
catches. There are some hints for drawing thick-walled tubing. When drawing
thick-walled tubing, it helps to have a draw bench for the extra force
that's required, and the sheet metal thickness that you start out with
is, more or less, the wall thickness of the tube that you end up with.
Definitely start with a fairly large diameter tube it is much easier to
make the tube that way and you end up with a lot more tubing. Again, for
the larger sizes, wood, Delrin and homemade steel (even unhardened) drawplates
will work. All you need are tapered holes in the plate. As always make
sure there are no overlaps at the seam.
Drawing wire inside
Sometimes a solid core is used to obtain a fixed size of hole in a drawn
tube. When the inside diameter needs to be a very exact size, goldsmiths
will draw a wire inside the tube at the same time as they're drawing the
tubing down. Usually you draw a tube with a core in it only a little bit
(through just a few holes) unless the core wire is much harder than the
tube material, as softer cores can bind really effectively into a tube
when drawn together. If you use a core, make sure that a good portion
of it projects out the end of the tube being drawn so as to allow you
to grip it and draw the core wire out again when done. A steel core wire
is best as core wires of softer materials may bind and snap off when you
are trying to withdraw them at the end. I like stainless steel the best
It can also help to lubricate the core wire with oil or graphite (a
pencil lead) prior to drawing to ease its eventual removal. A polished
wire core helps as well. The way that it would be removed at the end,
is by placing the back end of the tube against the drawplate with the
wire that's inside fitting through a hole in the drawplate, and then drawing
against the drawplate to withdraw the wire from the tube. A very good
selection of hard-drawn, high-polished, stainless steel wire in a number
of sizes is available from Small Parts Ltd. (see sources).
With a gold tube it is also possible to use a core wire of copper or
aluminum which is then etched out at the end of the drawing procedure.
This procedure is, however, time-consuming and involves dangerous acids
or caustic chemicals. Nitric acid, ferric chloride or even hydrochloric
acid are used for a copper core-depending upon which acid will not affect
the material of the tube that you drew around it: hydrochloric acid or
sodium hydroxide (lye) for an aluminum core wire. I have heard that people
who have done this got so impatient with the speed of the core removal
that they drilled a number of holes into the tube at different places
to allow the acid access and then had to plug the holes afterwards. So
in general, I don't recommend attempting to remove a wire from inside
the tube with acid. I think that if you have to resort to this approach,
there is probably something wrong in your design process and you should
be able to avoid this situation by more careful planning. Any acid use
would require proper safety equipment and chemical handling experience. If you do use a steel wire-not stainless, but ordinary steel wire-as
a core, for drawing inside, and if it by chance breaks off-and yes, I've
seen this happen-then we can remove the steel from inside by simmering
the tube, if it is a silver or gold tube, in a very concentrated solution
of alum and water. You purchase the alum at the supermarket-it's in the
pickling section-you make this concentrated solution, you simmer it, and
the iron will be eaten out. This method is also used for removing drill
bits when they break off inside a piece of jewelry.