I really appreciate your So... Harry.. you suggest
"centrifugal" is better than Vibratory (for my purpose)?"
I used the 3 main types of mass finishing equipment for close to 20
years on all types of jewelry and metals and each has their
advantages and disadvantages. Although the equipment and batches I
was running was far larger than for most jewelers, the results would
be similar for smaller equipment. Keep in mind that all tumblers are
dumb machines and wear down corners, sharp edges and pointy parts at
a higher rate than the center of flat designs. They are best for
highly modeled, rounded shapes, worst for crisp flat objects like
Rotary - the rolling barrel type tumbler.
Pros - These are quiet, easy and cheap to build and maintain and run
forever, easy to change the speed and the cutting action. The main
cutting action takes place as the media and pieces slide down the
face of rotating media. Can give a really nice finish, easiest on
sharp edges and best on center of flats.
Cons - Slowest of the 3 types and you can get more impinging if not
run correctly. (speed too high, too many parts, not enough water)
Vibratory - vibrating donut
Pros - Faster and better for fragile sculptural or heavy pieces than
a barrel. In a barrel, you can have problems with them beating each
other up. Pieces and media move in a toroidal ring around the bowl.
Can adjust the action from gentle to aggressive.
Cons - Noisy, you need a flow through system to keep the media clean
and to keep the parts cool. Because the motor is located below the
bowl, the parts and solution will heat up and can cause a slight
tarnishing to occur when burnishing. Sterling won’t come out bight
white, just a little off, we used to use a chiller to keep the
solution cool. Can be tough on motors too, we used to fry them
Centrifugal disc finisher - bowl with a spinning disc in the bottom
Pros - Fast, very, very fast. Pieces and media move in a toroidal
ring around the bowl, sort of like a vibratory on steroids.
Cons - Sometimes too fast, let parts go 10 minutes too long and they
might be toast. Chews up media quickly and all that friction causes
the solution to heat up quickly, needs a large flow through system
to keep the solution clean and flush out the ground up media. The
most aggressive and will wear down corners the fastest compared to
the center of a flat piece. Expensive.
Depending on the amount of money you’re planning on spending on
machine, you could probably get sample parts run in several types
and compare. Rio might do that for example. Be aware though that
media and how they are run can have a significant effect on the
finish. Like most things, if the operator is knowledgeable, you’ll
get better parts.
If I had to choose a system for wet finishing, I’d go with a rotary
tumbler. They’re simple, cheap to run and you can buy a Topline
barrel (the best IMHO) and build a base for less than a hundred
bucks that will last longer than any on the market. Run your parts
overnight in abrasive, an hour in steel shot the next day and you’re
done. I’m not a fan of the Harbor freight Lortone clones or real
Lortones for that matter, the small barrels take too long, and the
motors and bushings wear out. Also, the larger the barrel diameter,
the shorter the run time you’ll need.
For dry finishing (polishing) centrifugal is the way to go, suspend
your parts in a whirling mass of polishing media, much faster than
trying to accomplish it in either of the other 2 machines but you
pay for that speed.
Raytech has an small magnetic pin tumbler with interchangeable bowls
for centrifugal wet and dry finishing that looks intriguing and
might be good for small runs. Looks good at shows but I haven’t used
one in the shop.