Making a Magnetic Tumbler Part 1

Here you will find some basic information on the construction of a magnetic tumbler.

I have made almost 20 of these units using the same basic layout that is included on these pages, and the tumblers work as well as any commercial models I have seen. They can be made with hand tools and cost a fraction of the brand-name models.

The sketches included are rather rough and are not meant to be a working blueprint, rather they are to give anyone with the desire to construct a tumbler the basics of a working design.

Notes: The magnets must be neodymium-iron-boron rare-earth magnets. Any other type of magnet is not powerful enough or does not have the correct magnetic properties to work correctly. These magnets are expensive and VERY powerful, be careful when handling them because they will attract each other with enough force to severely pinch skin. The magnets WILL destroy the information on the magnetic strip on credit cards, remove your wallet before handling them. They will also render all magnetic media unusable - floppy discs, video tapes, audio tapes and computer backup tapes will be completely or partially erased. Sensitive electronic devices are also prone to damage by neodymium-iron-boron magnets, remove your watch, move your cel-phone and keep the magnets away from televisions, computers and computer monitors.

A two-speed (1250 rpm and 1750 rpm) evaporative cooler motor works very well in these tumblers. They can be purchased at Home Depot for about $60. The slow speed will provide a gentler tumbling action for delicate pieces, while the fast speed will work well for heavier items. 1/3 horsepower is more than adequate.

The electric motors come with a 1/2" or 5/8" shaft, while the sanding discs have a 1" hole, a 1" o.d. bushing with the correct i.d. for your motor shaft is required.

The magnets can be special ordered with a hole through them for a mounting screw. This is expensive and takes some time, so an alternative is to make a wooden disc the same diameter as the sanding disc with a thickness that matches the thickness of the magnets, drill 4 holes in this wooden disc and epoxy the magnets into those holes. It works well and I have not had a magnet come loose.

It is sometimes necessary to balance the disc, wood, magnet assembly if not constructed with critical detail. This can be done by either drilling small holes through the assembly or attaching weights

Plastic or another non-metal MUST be used for the top of the box. I first used a thin aluminum sheet, but even with no bowl of shot on the tumbler, the aluminum became so hot it could not be touched. The alternating poles of the magnets set up a weak inductive field, not unlike an inductive melter, and cause the aluminum to become quite hot

Plastic bowls are used to hold the shot, buy a few different bowls and give them a try. The results will vary depending on the items being tumbled, the amount of shot and water, and the type of tumbling compound used

The small stainless pins designed for magnetic tumblers must be used. They are available through most jewelry suppliers