Bending tubing

Jewelry Discussion
41 
Is there any concern about having some Cerrobend, Woods metal
residue remain in the tube after boiling & cleaning it out? I would
worry that if I didn't remove every speck that it would ruin the
gold tubing when I went to solder and assemble after bending?

Damned right there is a MAJOR concern. I use cerrobend mainly for
fixturing and holding the outside of pieces and am paranoid about
subsequent heating. Silicone mold release, poster paint, and very
careful visual inspection. I haven’t tried it yet but I suspect that
HCl might be useful too.

Still I use the stuff, too handy a tool to ignore (even good for
holding carving wax)

jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand

42

Kay,

of course you are correct. The Nylon monofilament does melt and run
out, however the burn out refers to continuing to heat the tubing to
dull red to ensure that no residue remains inside. Also be aware that
nylon and other plastics can emit noxious fumes when burning. The
quantity emitted from a few inches of fishing line however is
apparently negligible. But be aware nontheless.

John

43

Sorry if I did not make it clear, yes only into the ends about 15
mm. The copper wire saves the ends from collapsing, therefore less
wastage. I used to make loads of loads of ear rings fairly tight with
mainly 9ct with a wall thickness about 0.5 mm. Best to test a bit of
your material first. Though I am coming to the conclusion that
technology has overtaken me and probably go for some of the filler
options. I like the whippersnipper line idea. I am going to post a
technique I learnt in London from an old production jeweller. On my
Ganoksin blog: ‘On Your Metal’ soon which you will not believe, as I
did not till I made the tool and tried the technique.

David
Visit my website:
jewellerydavidcruickshank.com.au

44 
What if you formed a coil of the proper size using solid wire, then
using it as a mold, filled it with something that forms into a firm
material, something like Jett Sett. Then after removing the solid
wire you would have a shaped mandrel to use in forming the hollow
tubing, in the manner of tube benders for autos or conduit. Having
a shaped surface may assist in keeping any kinking/collapsing to a
minimum.

I’ve tried that approach once, and while it had the potential of
working, it was particularly sensitive to having everything just
right, or you couldn’t remove the coil from the plastic. If you
wanted a one off it would have been fine, but the original rod would
most likely need to be bent out of the mold (if you didn’t form the
spiral perfectly), and then the mold either cut or melted out
leaving no master.

However for a one off it may be an exceptionally fast way to do it.

Jason

45

Mike,

Is there any concern about having some Cerrobend, Woods metal
residue remain in the tube after boiling & cleaning it out?

Too right. In everything I have made (a lot for a hobbyist, not a
lot for a professional), the only commissions I have come a cropper
on have involved tubing which needed to be bent (check out

http://www.collarsandcuffs.co.uk/Webimages/cstick1.JPG

for an example - I spent UKP UKP sending these to be bent
professionally, which resulted in them being broken, me being
charged anyway and then spending three days soldering them back
together). Not tried the ice but will one day. Back to cerrobend,
tried using this on some 3mm id silver tubing a few years ago. Got
them bent OK, but it really liked the silver and was impossible to
get it all off (I took the usual precautions of greasing them up
before pouring in the alloy, so to do this right you would need to be
really, really careful). It was instructive watching them turn into
Swiss cheese when I tried to get them hot enough to solder
afterwards. I imagine gold would be similar.

Good luck.
CP
Collarsandcuffs.co.uk

46

I often use sterling tubing which is 4mm OD and 3mm ID. If I need to
bend it, I solder a small piece of sheet onto one end to seal it,
and then after pickling and thorough drying, fill it with aluminium
oxide powder (sandblasting medium which is really fine and pours well
if very dry). It needs to be tapped from time to time, to allow it to
reach the bottom of the tube, so that you can carry on filling with
the aid of a tiny funnel. I put tape over the open end and proceed
to bend. It empties out quite easily afterwards too. If soldering the
tubing into a circle, I leave the small piece of sheet in place,
soldering the open end onto it, and just file it flush afterwards
(not forgetting to drill a hole somewhere so that it doesn’t
explode!).

I guess ice might be an even simpler method.

Helen
UK

Note From Ganoksin Staff:
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47

I just saw a show on TV where they put soapy water in a tube and then
froze it, so they could bend the tube. Then they let the water melt
out… They were bending tubes for musical instruments.

laurie kern
http://lauriejanekern.ganoksin.com

48

Yes Jason, I see what you mean. Thanks for the comment. To work
properly you’d need one that has the diameter of the windings in a
consistent cylinder along the axis so it could be easily screwed
off, a difficult prospect if handmade with more than a few windings.
If making a number of items though, perhaps it would be cost
effective to have it machined from something slippery like high
density polymer.

Mike DeBurgh, GJG
Henderson, NV

49

Following up on my sugar idea, I think salt would work too. If the
granules are to large salt is easily ground more finely.

Mike DeBurgh, GJG
Henderson, NV

50

Helen’s comment about aluminum oxide powder prompted a thought. How
about powdered superfine or baker’s sugar? I wouldn’t use powdered
confectioner’s sugar because it doesn’t flow well, but superfine
might work if it is lump free. It would also dissolve easily in water
and it’s harmless.

I’ve never tried it, but the thought came to mind and I thought I’d
share it. I’ll give it a try after I get things set up again after
this move.

Mike DeBurgh, GJG
Alliance, OH

51 
If making a number of items though, perhaps it would be cost
effective to have it machined from something slippery like high
density polymer.

I bet that would work brilliantly! You could probably machine it on
a lathe set up to cut threads with a semicircular tool instead of a
point.

As far as packing material into a tube, I accidentally found out
just having finer particles isn’t enough by itself. I tried sand, and
a fine grade of silica powder head to head once. The sand wasn’t too
good, but it beat the tar out of the fine silica. The fine silica
wouldn’t pack very well, and all the fussing, tapping and cursing I
did apparently didn’t help. I think that a finer particle is best,
but it must pack tightly as well.

I ended up getting distracted and dropped the project before I ever
found a satisfactory solution, but I think that cerrobend or an
equivalent may be the way to go for one off situations.

Jason

52

One thing you all need to bear in mind is that, if you intend to
subsequently solder the tubing, every trace of the filling must be
removed or the solder joint will fail. Also, if something like salt
is used and just a few crystals get stuck in the tubing, they could
set up corrosion which would ruin the piece months or years down the
line… Best just to stick with frozen water - let it thaw out and
it all disappears leaving no residue.

Ian

53

This is a novel way of coiling tube that an old jeweller from Hatton
Garden, then the centre of the jewellery industry in London, told me
about. I still find it hard to believe although I have used it a lot
over 35 years.

Read more…
http://davidcruickshank.ganoksin.com/blogs/2010/01/26/

54 
Helen's comment about aluminum oxide powder prompted a thought.
How about powdered superfine or baker's sugar? I wouldn't use
powdered confectioner's sugar because it doesn't flow well, but
superfine might work if it is lump free. It would also dissolve
easily in water and it's harmless.

Well, I suggested toffee a few posts back, and not in jest. Though I
suppose ‘toffee’ may be a misnomer as my recipe was just sugar
water, without flour or butter.

I had heard bad reports from people who used frozen soap/ice
mixtures to bend tubing from brass instruments - apparently you have
to work very quickly in order to avoid it melting before you have
finished bending the tubing. Other people have expressed similar
concerns in this thread, and I suspect that if it is a problem for
1cm tubing it’s even more likely to be an issue for tubing only a
few mm wide.

I tried a boiled sugar/water mixture, heating it until it became
glassy then pouring it into the tubing (it shrinks a fair amount as
it cools). My reasoning was that toffee is an interesting substance;
not quite solid, not quite liquid. If you leave a sheet of it
hanging over the edge of a table for a while, it will start to flow
like a very viscous liquid. However if you hit it with a hammer, it
will smash like a brittle substance. The ductility seemed the sort
of property that would come in useful for bending tubing, yet it is
still solid enough that it acts as a solid base.

After filling a 1cm x 0.5mm brass tube with the toffee I bent it
over a wooden former, and couldn’t really tell the difference
between using toffee and Wood’s metal. It took a few hours to
dissolve out afterwards, with the tubing in a pot of boiling water.
I could also have simply melted it out by putting the tubing back in
a saucepan and heating it to melting temperature.

I’ve also heard of people using pitch, which works but can make a
mess.

Kit

55

I have watched the video with great interest. You say that you have
always used the tube dimensions as specificated and that you have
used this procedure for a number of years. What are you making with
this dimensione of coiled tubing? chain links?

The size is not small so I am curious as to what the final product
might be. Love the procedure.

Lois

56

Here’s some feed-back on the tube bending job…it’s a little low
tech, but it worked.

I needed to bend 2.5mm inside diameter gold tubing into rings that
were 21.5mm inside diameter. I used three pieces of 12" brass tubing
for this little experiment.

I cut a 1" diameter (about 25mm) wooden dowel to a length of about
8", then turned it on a lathe to a hair under 21mm in diameter while
leaving 2" on one end the original diameter.

I put the bigger, unturned end in a bench vise with the turned end
sticking straight up toward the ceiling.

Tube #1, I left this one unannealed and corked one end with wax,
filled it with salt (a little tricking getting it into the tiny
hole) and then capped the other end with wax. I clamped one end of
the tube to the dowel with a vise-grip, making sure it was
perpendicular to the dowel and that the vise-grip wouldn’t interfere
with the first wrap. I proceeded to bend the tubing by hand around
the dowel to form a coil. No kinks and it ended up about 23.2mm
inside diameter. I also had about 30mm of waste, 6mm from the vise
grip and the rest on the other end that wouldn’t bend.

Tube #2, I annealed this tube, filled it with salt and plugged the
ends. I clamped it the same way as #1 and coiled it around the dowel
by hand. It ended up 22mm inside diameter with about 12mm waste,
mostly because I gently tapped the end down with a mallet to curve
it.

Tube #3, I annealed this one but didn’t fill it with anything. I
clamped it the same way. It bent as well and easily as #2 but I
couldn’t curve or tap the end down, so it had more waste than #2. It
ended up about 21.8mm inside diameter.

So my humble conclusion was that filling with anything appears to be
most beneficial when trying to bend the end of the tube. If I didn’t
care about that bit of unused tube and would just be melting it down
anyway, there might not be a reason to fill it at all.

I was happy to find this wasn’t going to be a problem. I figure I’ll
use 24" long tubing and turn the dowel down a hair so end up closer
to my goal diameter.

I was fascinated by many of the tube bending posts, particularly the
Woods Metal possibilities and the steel shepards hook/draw plate
coiling method.

Mark