I believe I can help with your problems.
Yes, using a tumbler can speed the finishing process as long as it is
done right. As you have found out burnishing alone doesn’t work.
You won’t get the exact same results as hand polishing. But for
silver pieces very rarely can you sell them for what it costs to hand
polish. The first thing is to have the right tumbler and the right
media for each step. A Vibratory tumbler can work for all steps
depending on the piece.
Steel shot is a burnishing or final polishing for your pieces. It
can’t polish unless your piece is already smooth. No file marks and no
’sanding’ marks. Think of it this way. When you hand polish you don’t
just use say red rouge and skip all the other steps, right? It’s the
same with tumbling.
There is a difference between hand polishing and tumbling. A very
important one is the fact that buffing and hand polishing doesn’t take
metal off the surface. Basically it ‘moves’ it. The cut down steps of
tumbling will remove metal in order to create a surface that can be
polished/burnished using a burnishing media. This is important to know
because if your piece is left in the cut down steps too long you will
lose detail and possibly all detail. I’ve seen pieces in high
production shops that are difficult to tell they are the same as the
original. The original is usually very beautiful and without seeing it
you would think the tumbled piece is pretty as well but next to each
other the tumbled piece is very ugly. So with this in mind you may
want to exaggerate the detail on your pieces especially if the surface
is very rough and requires a good amount of time in the cut down.
There is some truth to the statement that you will need to experiment
but that is just after you understand what the process is and have put
some pieces through. All pieces are not created equal. Some will
require more time in the cut down and some less. Some will not fare
well in a vibratory tumbler and would do better in a barrel and only
big heavy pieces should be placed in a centrifugal disc machine.
Cent. disk machines create a tremendous amount of force and will
literally wad up a light ring or any filigree. As with all things in
the jewelry industry proper tumbling too is something that comes with
experience and is nearly impossible to write out on paper because the
variables in each style are different and since there are an infinite
number of designs you can quickly see that categorizing them would be
an impossible task. Sometimes it is hard to tell which type of tumbler
would be best. Another factor is how do you want the piece to look
when it is done. My idea of what it should look like may be different
than yours and everyone else’s.
Don’t say ‘I want it to look just like I hand polished it’ because it
The prep work for the first stage in tumbling is to:
If cast cut and grind sprue off.
If fabricating do whatever grinding you feel it needs.
When grinding use successively finer grits until you are using
approx. 40 micron. If you use a finer grit it may reduce the time
spent in the cut down media. However, if your pieces are cast, using a
grit finer than 40 micron most likely will be a waste of time.
At this point your pieces will be ready for the first stage of
tumbling. This is a cut down stage. You should use a 'medium cut’
media. Usually a pyramid shape will work very well but a cone can work
too. The difference is what areas of your piece do you want polished
with the media. A pyramid because of it’s sharp corners and edges will
polish deeper in grooves and filigree. However if these are areas you
don’t want polished then a ‘cone’ shape would be better. These shapes
can be mixed if you don’t want as much polishing of the deeper areas
to happen as you would get with the pyramids alone. If you are
oxidizing your piece you will not need to polish the crevices very
much so a cone might be better. But then maybe overall you don’t need
the crevices polished much but a certain spot needs it, then a
pyramid is probably better. Again some experimenting.
Medium cut media is used to get the surface to the same general
finish. That is to remove/reduce any large surface scratches made from
grinding or other processes.
The solution you use should be matched for the metal type and the
media. It should not be a burnishing solution. When the tumbler is
running several things are happening. The media is abrasive so it is
wearing itself down and taking a small layer of metal off your pieces.
The job of the solution is to suspend the debris so it doesn’t clog
the media. If this happens your media is useless. A good solution is
worth the money. Also a flow through unit on a vibratory tumbler is a
very good investment. A larger amount of solution means better ability
to keep particles away from the media. Once the solution has been used
it isn’t a good idea to reuse it. It’s cheaper to use new solution
than to replace your media. Make sure the solution is mixed according
to directions as too much can impede the media also.
The tumbling action is important as well. The media should be
traveling in a double circular motion. The first direction should be
around the bowl either clockwise or counter clockwise. The second
should move the pieces down to the bottom and then back up. If these
two actions are not happening some adjustments need to be made. First
there may be too many pieces in the tumbler so it is too heavy. This
usually won’t happen if your tumbler is made for steel shot. The other
adjustment has to do with the counter weight on the motor.
The amount of time depends on the beginning surface and the desired
ending surface. This takes some experience and a small amount of
experimentation. Again the longer you run it the more surface will be
taken off. The media doesn’t care what the surface is and therefore
will try to make the entire piece smooth. This means any high spots
(like a nose on a face) will be worn down more than crevices until
the high spots are no longer there. The cut down not only smoothes the
surface for burnishing but will remove any fire scale and oxides that
will change the color of your final piece.
It’s easy to say that mass finishing can save time and money but it
is give and take. The take is a difference in the finished look of the
piece as opposed to hand polishing.
If your pieces are not very rough like they would be from casting
then you may be able to skip this first stage.
The second stage is to use a ‘fine cut’ media. This media is the same
as the medium cut except it is less aggressive. So choose it the same
way. The same kind of solution can be used here.
After this stage your parts are ready for the steel shot.
To use carbon steel or stainless. It’s a big question. I prefer
stainless for several reasons. Most importantly it doesn’t rust. So
you won’t have to eventually throw it out and there is no upkeep. Just
rinse and go. If you use Stainless and have people working for you
make sure they understand this. I had a couple of ‘rookies’ that
didn’t understand this and for some unknown reason they threw out
about 150 Lbs. of stainless steel shot. OUCH! That hurt. Stainless
doesn’t have to be stored in a special solution to keep it from
rusting like carbon shot and therefore the cost of maintenance
solution and labor to maintain it over a short period of time will
start costing more than the difference between the two. In addition
carbon shot once it has started to rust you will have a headache and
a very difficult constant battle with it which will eventually lead to
the disposal of it. I have seen so many people think they were going
to save a bunch of money with carbon shot and instead created a big
problem and ended up getting rid of it and buying stainless. This cost
them much more than just starting with stainless.
Again the solution for steel shot needs to be made for the metals
(gold, silver, carbon steel or stainless steel…) and for burnishing.
This time the solution is again mainly used to suspend particles but
also to help the ‘final’ polishing. So again a flow through unit is
helpful and the time is dependent on the desired outcome.
All these steps can be shortened or lengthened and if you don’t like
the final outcome you can revert a step or two and run them again. So,
now that you have run your pieces and they still may not be as smooth
as you want depending on how much of the surface needs more work you
can run them through either both cut down steps or just the fine
followed again by the burnishing step.
A final note to the steel shot issue. Ceramic media can also be used
and creates a very nice burnished finish. Be sure to break in the
ceramic media before attempting to use it for burnishing. It will also
require a different solution for it’s use.
This may seem like a large investment in equipment and supplies but
if your pieces are in demand the trade off is that you can mass finish
many more pieces more quickly in the same amount of time than by
polishing by hand. Mass finishing will also allow you to capture the
market faster and can increase sales by having more product available
for sale than you would by hand polishing. You can’t sell what you
don’t have and people usually change their mind if they can’t get it
Generally a good place to start as far as times go is:
Medium cut run for 4 to 8 hours.
Fine cut run for 4 to 6 hours.
Burnishing with steel run for 2 to 4 hours.
These times will vary from design to design and if you practice
studying your pieces after they come out of each step you will develop
some experience for future designs and this will decrease your
Experimentation can be a disliked word but after understanding the
processes involved it can lead to more profit and new discoveries
which in turn can lead to more profits. More profit is what we are all
looking for, right?
If you have more questions or need more help let me know. i can be
reached at 877-262-2185 (toll free) or email at firstname.lastname@example.org. –
Ken Kotoski MPG Repair