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[Gadget] Old bur rotary burnisher


#1

Hi Jima :slight_smile:

As to why you’re getting that pitting, I’m not certain. What a
pest when it happens, particularly when you’ve worked so hard to
solder that seam under difficult/risky conditions. What I
sometimes do (after an initial filing)is to use a rotary
burnisher in my flex-shaft and smear metal over the porosity.
Then just emery and polish as usual. Pits all gone.

You can make one of these gadgets from an old bur. Nip off the
head and grind the tip to an equal thickness with the shank. Hold
about 1/4" of the shank in a vise and use your torch to heat the
shank enough to bend it with pliers to about a 45 degree angle.
When it’s cool, take it out and grind/sand/polish the tip to a
mirrorbright dome. Put the new bit in your flex-shaft and it
will whomp a thin metal smear where you want it. Kind of like a
spinning hammer. (note: anyone with corrections or improvements
to my technique here, feel free to jump in)

Hope this helps.

Jane


#2

The bent burr burnisher is almost a standard tool with people
who have to clean up platinum castings a lot, since getting
uniform porosity free castings in heavier platinum designs is
something the casters often cannot quite manage every time.
Especially with platinum, but also with gold, I’ve found that
such a burnisher made with a cap of carbide, polished with
diamond compound to a little hightly polished little hemishpere
end works much better than a steel one. It tends to work the
metal around without actually grabbing it and pulling it up, so
the result is even denser and smoother than you get with a steel
one. Making a little carbide tipped bent bur burnisher is a bit
of a chore compared to just the plain bent burr version, but
you’ll not regret it once you made it. Mine seems to be
frequently loaned to others in our shop who love it but are still
to lazy to make their own ((and why bother anyway… they can
borrow mine…))

Peter Rowe


#3

Hi Folks,

What I have done is to take a worn out #8 round carbide burr and
make a hexagon on it with a diamond burr. I then polish it to a
shine and use it to move metal.

Regards,
Skip


#4

One of the most important tasks when finishing a platinum
casting is burnishing. Yes, I know it takes extra time, yes, I
know hardly anyone is willing to do it but it is a fact of life.
Ideally you want to use a highly polished Tungston burnisher. I
do not recommend steel. In the gold leafing industry, there are
some wonderful agate burnishers. They are being used to burnish
the gold leaf into place. These work wonderful on platinum, as
they dont scratch, don’t contaminate and can be re-polished with
tin oxide or diamond . After filing and sanding your casting,
burnish the entire surface and then go on to polish. Your results
will be far superior.

have a platinum day
PLATINUM GUILD INTERNATIONAL USA
Jurgen J. Maerz
Manager of Technical Education
JA Certified Master bench Jeweler