Sunday, September 19, 2010

Using the Tumbler

Frequently, I remind myself that blacksmithing is an intrinsically dangerous business. That’s part of why I expect to be well paid for my work. I regard my tumbler as a nearly essential tool in my operation. When I finish forging a piece it goes into the tumbler. When I cut off a drop, it goes into the tumbler. If something needs removal of rust or paint, it goes in the tumbler. Twenty minutes of tumbling with small pieces of steel aggregate leaves the pieces clean and deburred.

I can only imagine how much time this has saved me. It also saved buying numerous, grinding discs, flap wheels, sanding belts, cup brushes, etc. Perhaps most importantly, I don’t have to breathe the dust produced by those other alternatives.

Three tumblers were built before I achieved what I needed. If I ever build another one I would make a few more small changes but I like what I have pretty well. It has an inside diameter of about 16” and a length of about 5’. Usually I have it loaded with about 50-100 pounds of steel aggregate, carbon steel balls, punch drops and other small odds and ends of scrap. It can easily accommodate another 200 pounds of work steel. I haven’t actually tried to test the upper limit. I’ve tried a number of other aggregates, stone, corncobs, walnut shells all with unhappy results. For me now it’s only steel.

Like a lot of other studio tools it is powerful and could inflict severe injury. I have special respect for those things which rotate. My setup is designed so that to turn on the machine I must open my garage door and turn the timer. Then I exit, pull down the door and lock it from the outside so I’m well away while it’s working. Incidentally, I’ve also locked the other studio doors so no one can enter while it’s running.

In addition to it having the rotation danger it is quite noisy, especially if it has some large mass pieces in the load. On rare occasions I do work in another area with ear plugs while it is running and it is tolerable for a few minutes.

A lot of “dust” is produced with each run - magnetite, hematite, paint, and more depending on what is being cleaned. To contain the dust and also add another safety barrier I cut a 55 gallon drum in half longitudinally and put half under the tumbler as a catch basin and hinged the top half so it folds down like a clam shell over the cylinder. Then I fold down a tarp which hangs nearly to the floor. The dust falls into the basin as the tumbler door seams rotate to the bottom and the tarp traps the airborne particulate and makes most of it fall so less circulates throughout the studio.

I recently welded four 5/8” square studs on the non-motor end so I can insert a dedicated custom socket wrench to turn the tumbler to the desired position for unloading. A floor stand supports the front side door in a level position so it serves as a shorting shelf when open.

Changes I would consider in a next generation tumbler are these:
1. Increase the length to accommodate 80” pieces and diameter to 22”.
2. Make the shaft on the non-motor end hollow so a vacuum/dust collector could be inserted.
3. Place the 1” square cylinder reinforcement ribs on the outside surface of the tumbler.
4. Make the interior baffles bolt mounted so I can experiment with covering the interior with rubber stall mat or similar material to diminish the noise. That’s possibly futile but I think it would be interesting to try.

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