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Size of workpiece dictate size of tumbler?

#1

Help, we don’t know what size tumbler to get. We’ve decided on a
vibratory tumbler which I believe would be faster than rotary for
polishing, and poss quieter. And we like the ones with a clear lid
and the way you can check the work easier.

However we do have to deal sometimes with quite big stg pieces:
55x30mm leaf shapes (2 1/4"x1 1/4").

http://www.adam.co.nz/ruthbaird/jewellery/brooch_pohu.htm
http://www.adam.co.nz/ruthbaird/jewellery/earrings_pohu.htm

Ruth saws the shapes out and files the edges, and the stg shape
backs a titanium/niobium leaf shape which is matt-surfaced, not
polished.

What would you say about the SIZE of tumbler needed? Does the size of
workpiece dictate size of machine?

Polish? I suppose there are thoser who would say there are several
degrees of polish. What sort of polish do we mean? Well, at the
moment we use white rouge on a 6" cloth mop on a slow (1400rpm)
motor. It’s not a super-high polish.

As it’s a big investment for us any help would be appreciated.

Brian

B r i a n A d a m a n d R u t h B a i r d

#2 
What would you say about the SIZE of tumbler needed? Does  the
size of workpiece dictate size of machine?

Absolutely. If the workpiece is too large for the tumbler, the
workpiece won’t turn properly and as a result won’t be polished
uniformly. The size of the tumbler determines both the quantity of
parts that can be polished as well as the size of the parts.

The diameter of the bowl alone will not tell you if your part will
fit because vibratory tumblers generally have a ‘cone’ in the
middle of the bowl surrounding the motor shaft. Measuring from the
inside wall of the bowl to the center cone will tell you if your
part will fit comfortably. Your best bet is to call the company
who makes or sells the tumbler you like, and tell them the size of
the part. They’ll help you determine which size tumbler will work
for that part.

By way of example, our # 10 Vibratory Tumbler measures about 2" from
the wall to the center cone of the bowl. So your 2-1/4" part is
too big for our # 10. The next size up is the # 25 Vibratory
Tumbler which measures about 3-1/2" from wall to center cone. So
this tumbler would work for your larger pieces.

However there’s a big price difference between those two tumblers
which means you have a decision to make. What percentage of your
production are those larger parts? Is the percentage high enough
– or is the polishing of them enough of a bottleneck in your
workday – to warrant the price of the larger tumbler? Or should
you get the smaller tumbler to handle the majority of your work
(small parts) and continue to do the large parts by hand?

I hope this has been helpful.

Best Regards,

Elaine Corwin
http://www.gesswein.com
Gesswein Co. Inc.
Bridgeport Connecticut USA
Tel: 1-800-544-2043 x287
Fax: 203-335-0300

#3

Brian - there are really two concerns in choosing a tumbler - the
size of the pieces you wish to finish, and the number of them that
you plan to run at the same time.

The jewelry needs to be able to turn freely in all directions in the
torroid of media that develops as you run the tumbler. Plan on 85%
media, minimum, and try and get your head around the number of leaves
that you will run and whether they might run into each other.

A first guess on the size you might need is a Raytech AV-25, 7.5
quart, 0.24 cf, 20 lb capacity. It would pretty much do all the
things you show on your website. Anything smaller would likely
create impingement problems with the pointy ends of the leaves.

The only downside to picking an over size tumbler is that you will
still always run it full of media, and the media wears itself out
eventually. Given the cost of tumblers, I’d go for a big one. It
takes a long time to wear out the abrasive media, and the bigger the
tumbler, in my experience, the faster it finishes.

Tumblers cost kind of like an employee for a week or two - but they
work at night, and weekends, don’t get sick, and are never asking for
two hour lunches. You gotta love 'em.

What you will miss is having to breathe the gunk from the buff,
backache from bending over the wheel, hot fingers. Need I say more?

Judy Hoch, G.G.
@Judy_Hoch
www.marstal.com