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Getting even contours


#1

hello, regarding finishing of precious metals, either a casting or a
fabricated piece:when filing or sanding, how do you keep a rounded?
or domed contour free of flat spots, even, & symetrical? do you
check to see if the light doesn’t shine off of the gold etc in a
snake like fashion, as you would with a cabochon. or does the
tripoli? cure this problem? ive read a few articles saying that the
sanding paper should be glued to a flat surface for finishing, but
i’m assuming this is generally only for a sprue on a casting. ive
never worked with gold so dont have the experience of this. ?

thanks for any advice in advance

joel


#2
how do you keep a rounded? or domed contour free of flat spots,
even, & symetrical? 

Take for example a simple round wire component. A basket setting
maybe. If you polish parallel to the length of the wire you will
definitely flatten the surface you are polishing.(because the buff
tends to hit only the highspot of the wire) If you polish at right
angle or even some other angle, you keep a ‘point’ to the wire. You
are polishing up towards the crown. I discovered this when doing body
work on cars. Basically you follow the crown of the curve and not its
long axis.

I much prefer a brush for this as opposed to any cloth wheel.

In cases of larger curved areas, a shank perhaps, the same idea
works but you need to polish with a systematic approach and a cloth
wheel. Let’s take a cast wedding band. On a tapered wooden mandrel
polish at 90 degrees to the band. Evenly rotate the mandrel as you
buff. Change the contact point relative to the curvature, after each
full rotation of the mandrel. Change to 60 or 45 degrees. Again, you
are polishing toward the crown. This also works with more aggressive
abrasives.

After you polish at an angle you can polish along the long axis just
to blend things a bit more.


#3

Joel

If you have cabochon experience you should already have a pretty
good eye, your comment on light reflection is spot on. Developing a
good eye for shaping and finishing elegant form to perfection is
essential and in my experience one of the weakness that I encounter
most frequently in jewellery workers who knock on my door. I also
migrated into goldwork from lapidary and my trained eye was one of my
advantages.

I’m sure that a lot of people will jump in on this one, so I’ll try
to catch this from a slightly different perspective. With skill,
experience, a good eye and a pair of trained hands you can develop
and control the surface with almost any firm cutting tool. I’ve seen
jewellers and even polishers get excellent results using some unusual
methods.

Assuming that you are at the bench and working with relatively small
objects, I would start with control; place a padded block in the
corner of your sweeps drawer firmly under your left elbow so that
your forearm angles upward to the bench pin. This will lock your hand
in place on the bench pin, almost like a swivel vise, you can of
course use arm movement if you need to sweep the work against the
tool but generally wrist movement is all you need. If you are using a
rotary handpiece with dressed wheels (angled to match the work)
support the forearm with the pull out armrest. Now you should have
the hand with the work in it fixed against the pin and the thumb from
the tool hand jammed against either the bench pin or against your
work holding thumb. You are now free to pull the cutting wheel
towards you and freely rotate or twist the work with firm and
complete control. Nothing is floating around in the air. With
experience you will find that this works for most of the things that
you do at the bench, especially with a handpiece.

The bench pin is where jewellery is made, the technique described
above was taught to me by a brilliant old master that distained
sloppy work habits, especially with handpieces. “Think like a milling
machine with your= two thumbs touching and your hands a pair of
interlocking swivel vises, both arms always supported. Your handpiece
is not a pencil poking at your work, grasp it firmly in the palm of
your hand not your fingers” there was more including a g= ood slap at
the back of the head, but you get the idea.

That said, I don’t recommend using a hand piece and shaped wheels
unless you have a lot of experience with them or a good background
cutting cabochons. I do, but I have thousands of hours behind me and
have used and shaped every kind of wheel imaginable, I have a trained
sense of what to use and when, which took years to develop. Even so I
use files and sanding sticks a some point on nearly every piece. I
must have a couple of hundred files in my drawer and I couldn’t live
without them. If you have the room to sweep over the work sanding
sticks are indispensable near the finial stages. Even the most
carefully formed surface will reveal minute irregularities under the
sweep of your sanding stick.

If you are only using files and sanding sticks then the technique is
different, with the wrist firmly semi-locked the whole arm holding
the tool is swept upward and forward at an angle over the contoured
surface of the work. Try to mimic the surface curvature of the work
with your arm movement, be sure to crosscut at about 45 degrees.
Twist and rotate your work to match the changes that you observe need
to be made. Here the rule is movement and speed. For this work you
still lock the holding hand in place but you clamp the work firmly
against the bench pin with your fingers. Keen observation and
constant adjustment are critical, after a while you get a feel for
the process and will develop a skill that you can be proud of and
create work with a wonder feeling of emotion.

Lighting and vision is very important in this work, I use a
combination incandescent and round florescent lamp, sometime two,
that I can position above the work or to one side. Sometimes I will
place it nearly over my head if that is the angle that I need. The
standard three bar florescent lamp is the worst light source for this
work. I took them off of the benches nearly fifteen years ago.

As in lapidary you work from course to fine, improving the surface
as you progress. Don’t use the polishing room to fix up the piece.
Your work should be perfectly shaped and nearly finished before it
leaves the bench. I usually prepolish at the bench, I’m already there
and the memory of the surface is fresh in my minds eye. I just chuck
a buff or an angled felt and touch the piece with rouge. I might use
a little white diamond on a mounted wheel brush sweeping it nearly
flat across the surface, it depends on what the work needs at that
point, Be sure to keep the work clean between the two. Finial colour
is brought up at the polishing machine, usually with a lead center
mop and a bit of rouge, again a light touch and quick cross-polishing
movement. Good luck.

Dennis Smith - thejewelmaker


#4

Joel,

LOL… I find that it is much easier to see if two lines are
parallel (or uniformly tapered) than trying to read a complex curved
surface. I’ll keep corners and flats for as long as possible in both
wax and metal.

My method of keeping a rounded surface fair and symmetrical is to
actually file flats. To go from a rectangular section band to a
comfort section I’ll chamfer all similar corners, chamfer width must
be even. Now chamfer the two corners you just created. Repeat until
you get tired or can’t see the width of the surfaces or the corners.
Emery with soft backed paper or an orange wax solvent if carving. I
usually just use my palm and fingers as the backing. With gold and
silver tripoli or bobbing can often replace the emery step, not with
platinum. It is also important to work all similar surfaces together
for symmetry, don’t completely do one side before starting on the
other.

Another symmetry tip is to realise that there is a bias in how your
hands move, file clockwise and flip the piece and file counter
clockwise.

Just be careful, I once was stuck with fixing another jewellers 20
finished rings with exactly the same problems you are facing;
instructions from far above for minimal weight loss of course :slight_smile:

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