Hi i was shopping around for a small tumbler, and when i saw how
basic they were i decided that i would try make my own since i will
only be tumbling one or two pieces a week. i have two questions, can
i use a glass barrel? and what is the average speed of a tumbler?
RPM’s?
thanks for all the wonderful ideas i get from this great community.
Louise
i have two questions, can i use a glass barrel? and what is the average speed of a tumbler? RPM's?
Louise, for the first question, absolutely not. The barrel is
designed to be soft but tough, so it doesn’t wear away in the
tumbling process, or damage the items being tumbled. Most tumbles
use a rubber barrel, or a plastic barrel that has the
characteristics of rubber. Glass would wear quickly, and most
likely break.
As to the rpm, it depends on the design of the barrel, and its size.
The idea behind a tumbler, and its name, is that you create a slope
of media and material in the tumbler barrel. As the barrel turns,
the slope reaches a point where the material can’t keep building on
the high side and “tumbles” down the slope. As the barrel is
turning at a constant speed, the slope remains constant and the
material keeps recycling through the rise to the top, and the
“tumble” down the slope. You will need a different RPM for a 4"
barrel vs a 12" barrel. If the barrel is faceted on the inside, you
will have a different RPM requirement to maintain the slope.
My suggestion is to purchase a small tumbler, the Loretone comes to
mind. I used to sell these tumblers in my store. They are designed
for the correct barrel and speed. They have an excellent track
record. They are reparable, and they last a lifetime or two. I
used to keep a 25 year old tumbler of theirs running in the store
for advertisement. Not many items that you can buy for less than
$50 today that have a long life and are cost effective to repair.
Don
Hello Louise, As to making your own tumbler, I suspect you could
purchase a small rock tumbler for less than the costs of assembling
a home-made one. However, sometimes it’s more fun to make it
yourself - you go girl. Anyway, I have used a fortuitiously sized
glass jar as a barrel on my tumbler, but only with dry walnut shell
media. I would hesitate to use a glass jar with metal or ceramic
media. It was necessary to put some wide rubber bands around the
jar - friction contacts between the jar and the rotating shaft upon
which it rested. Have fun with your project, Judy in Kansas
Judy M. Willingham, R.S.
Biological and Agricultural Engineering
237 Seaton Hall
Kansas State University
Manhattan KS 66506
(785) 532-2936
Hi Louise, There is an old publication, entitled Gem Tumbling and
Baroque Jewelry Making by the Victors. Published, at the time, by
Victor Agate Shop in Spokane, WA. Copyright 1962. I think this 60
page paperback is still available through jewelry suppliers and
lapidary shops. You might check with Rio Grande and/or Lapidary
Journal’s book department if you have trouble locating it.
I probably bought my copy, around age 10, in the early 70’s, and it
was already the twenty-third edition. Boy, does this little gem of a
book bring back memories! There is an extensive section in the book
about building tumblers. They indicate it is “essential” to have
variable speed, but I don’t think most of the commercial tumblers
today are variable speed. Among other things, the book contains a lot
of about belts and pulleys and rollers to get the speed
from a conventional electrical motor down to tumbling rotation
speeds.
As far as RPMs for tumbling, it shows one home made machine that
normally runs from 30 to 52 RPM, depending on the grit stage. It
states they have run it as high as 70 RPM for rough grinding, with
excellent results. They provide very detailed technical data to
determine the proper RPM for your barrel size to achieve the desired
sliding/tumbling effect inside the barrel. Larger barrels rotate at a
lesser RPM.
One example they provide is a barrel made from a 7" diameter paint
can… the result being 50 RPM, half of the calculated “critical
speed” of 100 RPM. It then goes into detail into how you can
calculate the pulley sizes and belt lengths you need to step down a
motor to the desired speed.
A great, and probably inexpensive book if anyone is looking at
getting into tumbling stone… especially if you’re interested in
building your own tumbler.
All the best,
Dave
Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)
dave@sebaste.com