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Dapping Distortion


#1

I am currently producing some earring designs, out of sterling
silver, which have a shape cut out of a circle and then the circle is
domed using a dapping block. As expected I get some distortion of the
cutout shape when doing the doming process. Unfortunately, the
distortion is often not consistent enough that I can easily account
for it in cutting out the design. For example, if I know the design
gets taller during doming I theoretically can make the cutout a bit
shorter than I want to account for the distortion. I think that a die
or two which does the cutting and doming on a hydraulic press would
be the ultimate answer but since I do not have a press and it is a
bit of an investment just to try a new design. I am looking for a
good way to try to better account for the distortion that takes place
and thus lower the product rejection rate.

Thanks,
Scott


#2
I get some distortion of the cutout shape when doing the doming
process. 

Unfortunately, the only solution I’ve found is to dome first, pierce
after. Makes the piercing process a whole lot more trouble, so if
anyone has a better soluion, I’d love to hear it. Pierce, super-glue
the pierced piece to a solid disc, dome them together then burn the
glue off? I don’t really think it would work.

Noel


#3

Hi Scott,

I am currently producing some earring designs, out of sterling
silver, which have a shape cut out of a circle and then the circle
is domed using a dapping block. As expected I get some distortion
of the cutout shape when doing the doming process. Unfortunately,
the distortion is often not consistent enough that I can easily
account for it in cutting out the design. 

The variation is probably caused by the way the doming punch is held
& struck when the item is domed. The way the blank is placed in the
doming form could also play a part.

Unless the blank is in exactly the same location in the form & the
punch is exactly vertical & the hammer hits the punch exactly at the
same angle there will be some variation in the force applied to the
blank. The amount of variation will depend on the deviation from the
exact location & angles.

About the only way to ensure location, force & angles stay the same
is by using a press of some type & a method of ensuring the blank
starts out in the same location.

One things machines are better at than hands/arms is repeatability.

Dave


#4

Would it be possible to dome the discs first, and then cut out the
shapes? Just a thought, and maybe a half-baked one…


#5

I pulled out my copy of Pauline Warg’s Making Metal Beads, to see
what she has to say on the subject, since doming is so integral to
this process. She has a project in which she creates beads out of a
pair of domes with matching pierced and sawn designs. In the project
instructions she specifies transferring the design onto the metal
disc and then scribing over the design. Then she drills her piercing
holes. She then anneals the metal and forms the domes and then saws
out the pierced design. She clearly states:

"...All piercing (I assume here she means sawing, based on the
pictures) must be done after the domes are formed to maintain
the shape of the domes, If the metal is pierced and then domed,
the domes will be distorted..." 

On the page following the instructions for this project, she has a
photo of a pair of earrings of her own design, made of pierced
domes, very intricate and beautiful. I would bet that she would be
willing to clarify this process for you and answer your questions if
you wrote to her. Her website is www.paulinewargdesigns.com. There’s
a contact link.

It is an excellent book (all those Lark books seem to be terrific)
and I think might be useful to you. I think you can search inside it
at Amazon to get a sense of what’s in it. I have not made much use
of it yet because learning other fabrication techniques have been
more pressing.

BTW, I don’t have a hydraulic press either, but wish I did. My
boyfriend (who is a metalsmith and sculptor who works in copper and
makes a lot of his own tools) says a hydraulic press is basically
just like a big car jack. He says he has a big old jack lying around
and is interested in seeing if he can turn it into a press when he
has some time. Hoping that will be soon.

Rachel


#6

I went to a laser class held by Rofin. They gave us handouts which
were reprints of articles written by David Brown in “The Bench” (Fall
& Winter 2003). The articles go into a lot of detail about the
effects of diddling (scientific term) the different settings.

The people who gave the class were out of the Boxborough, MA office.
They also have one in Tempe, AZ. It could be well worth your while
to contact them and see if you can wheedle a set out of them. Well
researched.

Justine Wetherington


#7
The variation is probably caused by the way the doming punch is
held & struck when the item is domed. The way the blank is placed
in the doming form could also play a part. 

The answer is in embracing the distortion instead of fighting it.

Cut out required shape exactly, but slightly thicker than required.
The taller the dome, the more extra thickness is required. Start with
small round punch following the outline of the shape on the inside of
cutout and some small distance from the edge. Place blows
strategically even spaced tracing the outline of the shape. Work on
flat anvil. Do not strike too hard! When outline is completed, the
shape should have some dome in it. Place another course closer to the
center and so on until degree of doming is achieved.

Correct mistakes in shape as you go. Use doming block only at the end
to refine the shape.

That should solve the problem.

Leonid Surpin
www.studioarete.com


#8
Unfortunately, the only solution I've found is to dome first,
pierce after. Makes the piercing process a whole lot more trouble,
so if anyone has a better soluion, I'd love to hear it. 

Noel…sorry for late reply…have been away for a few days over
the holiday.

An alternative to piercing after doming is to etch the metal!! Left
in the etchant long enough it will etch clear through the metal and
create perfect designs. Cheers from Don at The Charles Belle Studio
in SOFL where simple elegance IS fine jewelry!


#9

All,

Thanks for all the good advice on the dapping question. It appears
that the best solution is, as I feared, to dome and then pierce.
While this does increase the labor invested in the product, it
appears to be the simplest solution.

Thanks,
Scott