the common name for this alloy is Woods Metal.
Years ago Woods metal was used in the sprinkle systems seen in many
buildings. Each sprinkler head had a piece of Woods metal that held
the valve closed. If there was a fire in the area or the temp got
too hot the Woods metal would melt & the sprinkler would go off
stopping or at least slowing down the fire. I haven’t been around any
new installations, so I don’t know if it’s still used today.
Dave
This technique works well.
This is a question close to my own interest, which is making brass
instruments.
I have had some success with toffee (seriously), which I tried
because bending alloys in the quantities I needed were prohibitively
expensive. I suspect that for the sizes of materials you’re working
with, that’s less of an issue. After you’re done bending the tubing,
you just leave it in warm water for a few hours, and the toffee
melts out. For fine diameter tubing the bubbles that form in melted
toffee might cause problems.
Some brass instrument manufacturers use a teflon rod inside of the
tubing, which they pull out gradually as they bend it. Again,
whether it would work for the sizes of tubing you’re talking about,
I don’t know.
In your position, I think I’d splash out on a few grams of Cerrobend
but I thought it might be interesting to mention these alternatives.
Kit
At my first SNAG conference in Portland there was a presentation by
the head of Monet Trumpets which produced beautiful hand built
trumpets. They used a filler (such as Wood’s metal, Cerrobend, etc.)
to bend the brass tube and pipe prior to soldering.
It was a wonderful presentation that ended with a player from the
Portland Symphony playing a commercially produced trumpet and then a
Monet.
Even to my tone challenged ear the difference was easily heard.
Andy
Using Cerrobend sounds fine - in theory, but have you actually tried filling a 2.5mm OD tube with it? If you can actually do it, will it come out of a coiled tube afterwards? I seriously doubt it.
If the tube diameter is small the heated Cerrobend can be lifted
into the tube, if the tube is heated as well, with a cheap hand
vacuum pump. A small clear bottle between the tube and pump can be
used to confirm full fill.
I would try heating the Cerrobend and a long straight piece of scrap
steel at the same time (separately of course), and when ready, twist
tie the steel piece to the tube to heat it and then vacuum.
Daniel Culver
I don’t know what size tubing you are trying to bend - But here’s
how the folks who make trombones and trumpets bend their very
thin-walled brass tubes. Cut your tubing a bit over-length. Cap one
end of the tube by soldering on a cap or by crimping it tightly
closed. Hold the tube with open end upwards and fill the tube with
water right up to the top. Crimp that upper end closed tightly losing
as little water as possible. Now put the tube in the freezer and when
the water is good and frozen you can take the tube out and quickly
bend it around a form of the desired radius. The tube cannot collapse
because of the ice inside. Then let the ice melt, cut off the crimped
ends and there you are. You’ll have a wee bit of waste (the cut-off
ends) but what’s life without a little waste?
Do not try to melt out the ice with a torch before you open at least
one end of the tube or you might have a wee explosion or at least a
jet of very hot steam forced out of a crack or hole. Just put the
bent tube in warm water in the sink or something simple like that.
Marty in Victoria BC.
I have no idea if these will help at all, but I thought I’d throw it
out there in case they would work for what you want to do.
Check out Micro - Mark.com under Vises,Anvils,Punches, Benders. They
have several mini versions of industrial type machines including
benders. Theone I like is the bending machine that does sheet, wire
and tubing from 1/16 to 1/8 dia without filling or plugging. its also
adjustable for different dia. I have not purchased one yet but plan
to very soon along with several of there other machines. This
particular device is like an industrial rolling machine just
smaller. It should work well for making all types of round bends.
especially if metals are annealed.
Rick McC.
I went home and looked at my various tools for bending tubing and
remembered that they all will cause at least a small amount of
flattening or collapsing of the outside diameter. This isn’t a
problem when the tubing is intended for fluid flow, but for your
project Mark, it might render the tubing unusable. I also found that
if you put one of the small wheels (3/16 or 3mm) from a brake line
tool in a lathe or even a flexshaft you can turn it down to the right
diameter and width for the tubing saving all the hassle of making a
mandrel from scratch. It could then be used either in brake tool
pliers or cut in a “D” shape then mounted in a vise with a pin to
help cut down on tubing waste.
As you said, maybe using Cerrobend, ice or even the copper wire and
acid bath technique and a tool made or purchased for bending tubing
might be the best solution for making the tubing coils you need with
minimal marring. I’d never heard of Cerrobend or the ice trick
before. That’s why I love Orchid! I learn so much from you all.
Whatever route you take Mark, I hope you’ll report back on what you
did and how it worked. I for one, sure would like to know. Being able
to make perfectly round rings out of tubing is a skill I would love
to have. Think of the possibilities!
Does anyone know how the larger commercial gold jewelry
manufacturers make curved hollow tubing for things like hoop earrings
and San Marco (“macaroni”) bracelets? Some of that stuff is pretty
thin walled (to the point you can almost read through it), but it’s
still evenly and smoothly formed. I’m guessing some is electroformed,
but some of it has seams and is obviously fabricated in some manner.
Is it die-struck or hydroformed in pieces then assembled? Or even DOM
(drawn-over-mandrel)? They’re too cheap to be done using the kind of
labor intensive techniques we’re talking about here, I would think.
There must be an easier way, or are the techniques and tools used
like DOM, and only viable for producing hoops by the thousands?
Dave Phelps
There are a few low temp melting alloys available. Woods Metal has
been mentioned as well as Cerrosafe. Although they have the same
alloy components, the proportions differ for each of them.
Cerrosafe:
(% by wt) Bismuth 42.5%, Lead 37.7%, Tin 11.3%, Cadmium 8.5%.
Woods Metal:
(% by wt) Bismuth 50%, Lead 25% Tin 12.5%, Cadmium 12.5%.
Woods Metal is known to swell upon cooling and can be difficult to
remove as a positive casting. Cerrosafe, on the other hand, contracts
in the first 30 minutes, then swells afterwards as follows:
. 2 minutes -.0004"
. 6 minutes -.0007"
. 30 minutes -.0009"
. 1 hour +-.0000"
. 2 hours +.0016"
. 5 hours +.0018"
. 7 hours +.0019"
. 10 hours +.0019"
. 24 hours +.0022"
. 96 hours +.0025"
. 200 hours +.0025"
. 500 hours +.0025"
For applications requiring the greatest precision in measurement a
Cerrosafe casting is measured after 60 minutes. The rate of
contraction and expansion is well known by toolmakers.
Woods Metal melts between 163.4F and 170.6F. Cerrosafe melts between
158F and 190.4F. Both will melt at less than the boiling point of
water. Many suggest that a double boiling arrangement be used to melt
them without direct heat. Seeing that both lead and cadmium are
alloys of both, the application of direct heat could be deemed a bad
idea.
For use in filling a 2.5mm ID tube I would choose the Cerrosafe. I’d
use a turkey baster made of metal. I can see plugging the hole with
high temp RTV, then after curing, making a hole in which to place the
tube. I’d wrap the tube in something like aluminum foil (a few
layers), then warm it in boiling water or in a steamer while hooked
up to the baster. When the Cerrosafe was melted I’d quickly place the
tube into it and use the bulb of the baster to draw it into the tube.
A few layers of folded aluminum foil would be enough to hold against
the end of the tube to prevent it from running out before cooling.
Once cooled you could easily wrap it around a mandrel, cut it, then
boil it in water to remove the Cerrosafe. Once the water has cooled,
I’m sure you could gather the Cerrosafe, dry it, and reuse it.
As Orchid readers are aware, there is always more than one way to
skin a cat. I’m sure there are other’s that’ll have better ways to
skin this one.
Mike DeBurgh, GJG
Alliance, OH
Regarding using ice for bending tubing. I had occasion to repair the
copper tube that brings water service into my new home. Thieves had
come into the basement and cut it to steal the copper piping. I had
to dig it up, add a butt connector, then add a new piece to extend
it beyond the wall. I also wanted to bend the tube so the new piece
came out perpendicular to the wall. Because the water was frozen I
was able to bend the tube without kinks even though some good amount
of force was needed to bring it to the right direction.
Despite my exposition about Cerrosafe, I’d favor using ice in a
first attempt.
Mike DeBurgh, GJG
Alliance, OH
Of course, it would be a whole lot more helpful if I actually
included the link!
Hans,
Thank you for the link to your great “bending tubing” demo. Clear,
concise and to the point, yet very informative and self explanatory
with great pictures.
A must see.
Bravo!
Cyrille
As I was reading Dave Phelps response a thought came to mind. 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.
Mike DeBurgh, GJG
Alliance, OH
By the way how long are the lengths?
They are 12" -24", so pretty long.
Find a piece of pipe, or steel just a bit smaller than the diameter of the ID of the rings you need to make. Make a piece of copper wire to fittightly just into the end of the tube...Insert into the tube about 15 mm and carefully bend that end around the mandril set vertically in a vice....Prepare a second piece of copper wire to go into the other end of the tube. Start bending the wire and the tube... hold the bent end as you carefully coil the rest of the length around the mandril, when you reach the end just continue to coil the copper a bit. Remove copper....You should have a perfect coil...
David, you are just fitting copper wire into each end of the tube
about 15mm? Nothing in the center of the tube? And then just bending
it manually, by hand, around the mandrel? And you are left with a
nice smooth coil?
Thanks,
Mark
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?
Mark
Hi Laura;
I have been silently reading all of the posts in regards to bending
tubing as I am at present making a pair of hollow hoop earrings. I
too have found the website for micro mark but I live in Canada and
the shipping on that item is $25.00. Ouch!!! Does anyone on this
forum know of a supplier within Canada?
Take care,
Paul LeMay, Bracebridge, Ontario. Canada
When bending small OD tubing I usually use monofilament fishing line
(a tip from Tim McCreight’s Complete Metalsmith), this is available
in a variety of diameters and burns out easily after the bending. For
larger diameters I expect one could use “Weed Whacker” line (much
cheaper than high strength fishing line and available in smaller
spools - who really wants 200 yards of 150 lb fishing line ??). The
trick is to use larger than needed while drawing the tubing, ending
up with a tight fit when the tubing is drawn to the correct OD.
John
John Bowling
I would choose the Cerrosafe.
It should be clear that bending tubing just requires that you make
it “temporarily” solid with anything that does the job - ice…
Mike mentioned Cerrosafe, which made me curious. Interesting stuff,
that. Gunsmiths will pour it into the chamber of a rifle, let it
cool, at which point it has shrunk so it can be removed. Then over
the course of an hour it expands at a given amount, and it gives an
exact plug of the inside of the chamber. One page that gives some
ideas of how some of these alloys are used (Just Googled
Cerrosafe…) is here:
http://www.hitechalloys.com/hitechalloys_002.htm
Interesting stuff…
John: How do you “burn” it out. I didn’t think monofilament fishing
line would burn. It would just melt wouldn’t it?
Kay