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Wedding band stretcher


#1

Hi Everyone:

I have 15 years experience as a bench jeweller/goldsmith. Recently I
bought a new Italian wedding band stretcher/compressor. The type with
the split mandrel extending vertically with the compresser directly
below with a removable steel disc containing concave depressions- the
most popular unit. I have used these machines for years so I am no
novice, I can’t reduce the size of a wedding band without distorting
it. The concave depressions keep throwing the work off centre so my
bands are getting skewed.

Any thoughts??? I thought that maybe grease on the bottom of the
plunger was possibly sticking to the top of the wedding bands and
causing it to be thown off, I also thought that maybe I need to high
polish the concave depressions. The plunger seems to be 90 degrees to
the disc bed, and my wedding bands start out parallel to the bed. I
am out of ideas.

Any advice/ help would be much appreciated!

Thanks in advance
Cary James


#2

Make sure you aren’t trying to size the band in one shot. You have
to do it in stages. First, set the band into one of the depressions.
If the band sits in the depression so that the edge of the band is
visible above the edge of the depression, move the band to the next
larger depression and check it from the side again. Keep moving the
band to larger depressions until you can see that the plunger will
not compress the band. The next smaller depression will be your
starting point. Compress the band in this first depression, then turn
the band over in the depression and compress again. I’m sure you
realize this is done for the same reason you flip the ring over when
sizing on a mandrel (or triblet) - to prevent distortion. Check the
new, smaller size on a triblet (or mandrel) every time you compress
the band to make sure you don’t overshoot your intended size. Two
tips: Wrap the outside of the band with a bit of masking tape to
minimize marring. This also helps with many textured bands. I’ve had
a lot of luck, even with florentine finishes. Second tip is to anneal
the band for every ring size you reduce or stretch. I’ve compressed
as far as two sizes without annealing, but I don’t recommend it.

James S. Duncan, G.G.
James in SoFL


#3

Thanks James: I was taking my time and going slowly-I even did as you
suggested and placed it in the largest bowl that it would fit in and
still have some edge of the wedding band sticking up out of the disc
with the bowl shaped depressions. I usually give the bands a light
tap with the plunger to set them at 90 degreesfrom the plunger before
I press down, but I think that for some reason this is throwing them
off. I am going to try again next week-I sound like a rookie but this
is driving me nuts!

Cary


#4
I usually give the bands a light tap with the plunger to set them
at 90 degreesfrom the plunger before I press down, but I think
that for some reason this is throwing them Off 

Aha! Yes, that very well may be the cause of your problem, Cary. The
"tap" is unnecessary, since the plunger itself “squares” the ring
evenly into the depression. Skip that step and you should lose the
distortion. Let us know.

James S. Duncan, G.G.
James in SoFL


#5

Cary, from everything that you describe you are doing it perfectly.
You obviously have experience with this tool. I use my stretcher for
so many things…

I hesitate to blame a tool for a job gone awry, but perhaps the
milling is off on the reduction dies. Do you still have the old
stretcher or a friend who has one? If so, compress a ring on another
machine to test your technique. Also test another ring in your
machine. Once you – or the ring-- have been eliminated as variables,
the culprit must be the machine itself.

The only time I have had problems is some uneveness in the band,
such as a solder lump or uneven annealing was the problem. I am often
suspicious when a new tool yields problems that an old tool never
did.

Good luck,
Andy Cooperman


#6

Hi Cary,

Re the wedding band compressor producing skewed rings; the wedding
band must be uniform in section all around in order to compress
uniformly. If the wedding band is thinner at one edge in one place,
it will compress in a skewed manner. Seamless machine made wedders
are very uniform and will srtetch or compress without problems. Old
worn-out wedders, specially if thin and wide, will definately
compress skewed and are better sized by cutting and joining.

To correct a skewed ring, hammer the appropriate edges on a mandrel
in order to get the ring square on the mandrel, then size by cutting
and joining. Unfortunately the thin spots on the ring will be even
thinner after the hammering.

Regards, Alastair