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Making very thick copper tube


#1

Hello everyone,

I am an enameler and my metalworking abilities are limited. I can
saw pretty well, soldering basics and so on. I make my own settings.
My equipment is also limited.

For a project, I have to make a copper cylinder, 2 mm thick (a must)
and about 4.5 to 5 cm in diameter. I want to make this from sheet,
to be able to saw the intricate designs first and then solder it
closed. I know it is not going to be easy to curve such a thick sheet
into as perfect a cylinder as I can. I will have to conform to a
precise outside and inside diameter (just don’t know exactly how wide
yet, this will have to fit around a wooden box).

The length of the tube I still have to decide. I guess the longer it
is, the more difficult it will be to form it. I was estimating
between 5 and 7 cm long.

I have a ring mandrel, which of course is tapered, and a good big
boxwood hammer. The biggest measurement of my mandrel will most
likely be too small, but it may help for shaping.

I am thinking I may need a wooden dowel of a slightly smaller inner
circumference as well? the wood turner that is making the box for me
can make one to my measurements, of hard wood. Or I may find a pine
wood dowel of approximate measurements in the hardware store.

I see a lot of annealing in my near future.

I may have other problems afterwards with the solder and the enamel
and possible tension deformation, but that is for later…

Any advice would be greatly appreciated.

Cheers,
Mer
www.innershelter.net


#2

You need to buy, make, or borrow a set of small bending rolls. There
are two basic designs, both use 3 rollers, and are designed
specifically for smoothly bending sheet metal. Model engineers use
them, for example, for making the boilers for steam engines.

This link shows a typical set, but they are widely available from a
number of sources - just Google “bending rolls”.

http://www.hemingwaykits.com/acatalog/copy_of_Bending_Rolls.html

Regards, Gary Wooding


#3

Hi Mer,

I do not understand why you need to cylinder of 2 mm thick copper.
Can you explain why this is a must? I am not aware of anyone
enamelling on sheet that is so thick nor can I see the necessity for
it.

Ch. Lewton-Brain writes in his book on Foldforming that the best way
to anneal copper is to heat it up to dull red and quench it. I have
done this.

I have also annealed copper in a kiln, heating it up to bright orange

  • almost yellow - leaving it there for a minute or so before
    quenching it in water. It is remarkable that the second way gives a
    much better result. It is hardly believable how extremely soft the
    copper becomes. Feel free to contact me off-line. It’s always nice to
    talk to a fellow enamellist.

Leach


#4

I would go to a hardware store and get some pieces of iron pipe to
use as a mandrel. You can probably get a fairly short piece.

Peter B. Wolff
Gold Wolff Jewelers


#5

Hello Gary,

Many thanks for your input. I didn’t know about these machines. I
see the German shop where I buy my tools has something similar:

http://tinyurl.com/39ngsy4

It is too expensive for me to buy at this moment, though, and I
don’t know if I would use it again. I wonder is there are smaller
hobby tools of this sort. I don’t know anyone that may have such a
tool.

Another thing I am concerned about, since the copper would be
compressed between two sheets of steel, is deformation, of the
thickness, lenght, and my pierced design.

Perhaps I can do something similar with wood, as someone suggested
in the metalsmithing livejournal community, by using a wooden dowel
against a groove in a wooden piece. The copper would then be
compressed between wood and not deformed. Has to be much harder to
do, though.

Regards,
Mer
www.innershelter.net


#6
do not understand why you need to cylinder of 2 mm thick copper.
Can you explain why this is a must? 

I thought it was a school assignment, I’ve had a class with that
assignment.

Elaine
http://www.CreativeTextureTools.com


#7

Hello Leach,

The reason is that the enamel is to be plique-a-jour. I won’t enamel
on the copper, but the holes I pierce out. 2mm is actually rather
shallow for this. I really don’t want to deal with shallower holes!

Many thanks for the tip on quenching. I didn’t know this. I can
definitely anneal in the kiln. Extremely soft? That would certainly
help in this case!

Regards,
Mer
www.innershelter.net


#8

Hi Mer,

Is there any reason that you can’t buy a section of copper tube the
dimensions you want? When you find out your final measurements you
might be lucky and find a tube that is close or exact.

Regardless, 2 mm copper wont be that hard to bend, and the
suggestion by Pete Wolffe of using a piece of pipe from a hardware
store is perfect. Bend what you can by hand, then hammer the ends
closed.

You probably wouldn’t have to anneal the copper, but better safer
than sorry.

Median diameter x Pi will give you the length you require. Median
diameter is inside diameter plus one metal thickness.

Using the above formulae:-

4.5 cm will give you a length of 14.77 cm

5 cm will give you a length of 16.34 cm

Regards Charles A.


#9

Hello Mer,

Bending rolls simply bend, they don’t squeeze, they simply grip. The
diagram shown here http://tinyurl.com/2wcknde shows how one type
works. Rollers A and B are geared together so that they rotate as
shown when a crank handle is turned, the gap between them can be
adjusted to grip the sheet between them. The position of C is
adjusted to give the desired amount of bend to the sheet as it is
pushed over it. Multiple passes are required; roller C is adjusted
each time to increase the bend until its just right. Roller A is
hinged at one end with a clamp at the other. Releasing the clamp
allows the roller to be lifted to allow the final cylinder to be
removed. The beauty of using bending rolls is that pierced sheet can
be bent properly if it is sandwiched between two other sheets. I’ve
done it with stainless steel.

Regards, Gary Wooding


#10

Mer,

My standard advice for almost all problems, a hammer, size as
required. Wood in your case so as not to cause too much damage to
very soft copper. Figure out the length needed and curve the ends
first then the rest. Solder and then beat it into a reasonable
approximation of a cylinder. More accuracy and use a roll former,
dead on, and use a lathe to bore and turn the needed dimensions and
make lots of scrap stuff.

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


#11

Why not just go to a plumbing supply house or neighborhood home
store and buy it already made? I have found it in 3/32" inner
diameter to inches in openings and at least 2mm thick…the stuff you
seem to be describing comes on a roll and is dead soft and quite
cheap and pure copper !..rer


#12

Hello Charles,

Thank you. Yes, I have to pierce the sheet with a design, and the
holes will be wider on the exterior than the interior of the tube
(like an arrowslit seen from the inside). I think this will be very
difficult to do once the tube is closed, or on a closed tube.

I have found a wooden (beech) pickaxe handle that is 4cm in
diameter. The exterior will be 4.5 cm, so interior of 4.1, so I think
this rod will be good for this. I couldn’t find pipe so big, and
perhaps wood will be good not to mark or deform the copper. At least
I hope so.

I was calculating the length wrong, I see. I was using Pi x inside
diameter + two metal thicknesses. Oops. I think I saw this here on
Orchid when reading about ring perimeters, though.

Regards,
Mer


#13

Hi Mer, I am sorry to say, but I think that you are making a
mistake. You do not need two mm thick metal to make plique a jour. No
one does that. If I make plique a jour, I use 0.70, which is more
than enough. Two mm thick enamel will not look transparent; it just
defeats the purpose. You will need to use a lot of enamel to push
into the holes and if there is an impurity, you can start drilling.

Leach


#14

Hi Mer,

Doing the piercing and cutting on a flat sheet will be a lot easier
imo, although piercing a series of holes and filing can be done on a
tube. The holes could be straight and not tapered if you work a piece
of tube. I suppose the holes could be straight if you did an angled
cut on a piece of sheet before you bent it… meh.

You’ll be safe with the wood, although a rawhide hammer on a steel
mandrel does work too.

Just remember “median diameter = inside diameter + one metal
thickness” Sometimes you can use two metal thicknesses, but I
haven’t been told under what circumstances.

Regards Charles A.


#15

Hello Alicia,

I do not mean to be rude, but I know perfectly well what I am doing.
I worked in a plique-a-jour workshop for 3 years, 8 hours a day, and
have 15 years enamelling experience. See for yourself if enamelling
in 2mm deep holes can be transparent: www.masriera.es

There are many ways to do things. Shallow plique-a-jour is possible,
and I assume you are using a backing of some sort, or small holes. I
do this with water tension, no glue, and deeper holes can be
desirable, and rather big holes possible. I fill the holes with flux
first if I want the colours to be lighter. I wash my enamels so that
they are clean, no impurities, no bubbles. My main enemy won’t be
the depth, but the firescale, the only mistake that I could be doing
here is using copper, but I can’t afford silver or gold of such
thickness at this moment. I will have to fill the holes with flux,
then once closed give a good fire to purify the flux, then work from
there. I need some extra depth. Could perhaps do with 1.5mm in silver
or in gold.

Hello Charles,

I actually want the holes to be tapered, this helps having a base
for the enamel to rest on. They will naturally taper as the sheet is
bent, but I may want an even wider taper. I will do some tests.

Thanks everyone for your help on this!!

Regards,
Mer


#16

Hi Mer,

I’m simply overwhelmed with the “Offering of Love” ring on the
Masriera website. Thank you for the link.

Would you mind explaining to this beginner what it means when you
said “… I do this with water tension…” ? All I can visualize
is wet packing, but I’m wondering if your meaning is something
different.

When you said “… My main enemy won’t be the depth, but the
firescale…”, I’m wondering if, between firings, do you have to
grind it off where the enamel touches the copper, and if so, what
tool do you use?

Many Thanks,
Betty


#17

Hello Betty,

Yes, wet packing. You can read about surface water tension in
Wikipedia to understand what the water is doing there. This is quite
a strong force, what makes water form drops. Basically you contain
the enamel within a drop within the hole. No more is necessary. But
the fires are delicate (can’t fire to glossy until the hole is well
filled, takes many trips to the kiln).

I am now sawing some copper to make tests. I have done plique-a-jour
on copper before, but with mica backing, which in the case of copper
helps since you can fill up the hole from the beginning to avoid
firescale.

In this case I will have to get rid of firescale by one or other
means. I think I may have to use acid, possibly hydrofluoric. It
cleans firescale, and also eats at the enamel, but doesn’t spoil the
remaining enamel like nitric can sometimes. I will say no more, this
acid is very dangerous and I cannot recommend its use. I am
experienced with it but still approach it with a lot of respect.

Grinding can work in some circumstances, but you may lose metal and
can spoil the design or surface. Diamond burrs work great.

If at all possible, silver and gold will work much better and
easier, acid is not necessary.

Rgds,
Mer


#18

Mer, Experience, so what? No one makes two mm thick plique a jour
because the whole purpose of plique a jour is to make it as light,
thin and elegant as possible. Perhaps you are making windows for a
church?

Leach


#19

Leach,

I am surprised that you belittle Mer’s experience as an enamelist.

Have you checked out the website Mer suggested. You will find that
the pieces shown are plique a jour on thick copper. Mer is an highly
regarded enamelist, with many years of professional experience with
a company that specializes in plique a jour made with thick copper.

Alma


#20

Leach,

Plique a jour does not have to be made with thin wires. There is a
highly detailed article in Glass on Metal, written by Bill Helwig in
which he details doing plique a jour using 18 gauge silver wire, and
also another example of one done on 16 gauge copper. The article
appeared in Vol.21, No.4, August 2002. You can download the complete
article from the Glass on Metal Website.

Using the method described by Bill Helwig, one would not have a
problem using copper that is 2mm thick.

Alma.