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Question on magnetic pin finishers (and another on sprue removal)

I’ve had some rings cast, and am now looking into finishing larger quantities efficiently.

Most of the work, though not all, will be very textured.

I’m thinking in terms of a magnetic pin tumbler, and I’m thinking of a model that has a larger (in this case 100 ring) capacity) on the idea that you’re going to spend a fair amount of money in any event, so you might as well spend a bit more and be ready to move to larger quantities.

Every thing I’ve read about these seems to say that they’ll take rings to almost all the way finished pretty rapidly, with only minimal work required after that.

I’m kind of assuming that I’ll have to run something on the insides of the shanks.

One thing that I’ve read is that they leave a flat surface looking frosted. It this something that can be polished up quickly in a second step?

Also, if parts of the exteriors of the rings are smooth, how do the machines leave those?

Lastly, in terms of sanding down the remains of sprues, while I’ve seen fairly impressive video’s of Jool Tools (Made by the manufacture/distributor, natch), I’m not sure that they would be any better than a belt sander. Thoughts?

I would love to be proven wrong, but I have serious doubts about any magnetic finisher that claims to take a piece to nearly finished. We use a combination of wet stone tumbling, followed by magnetic pin tumbling, and then either finished by hand, or in a walnut media polisher. No matter what, we still end up needing quite a fair bit of hand finishing. But, the pieces we cast are typically quite detailed, and have a myriad of nooks and crannys that the pin media just can’t get in to reliably.

As far as the Jool Tools, I think they’re great little machines, but I can’t recommend spending 500 bucks on something that only costs about $20 to make (we actually built our own after the one we had died). But if money isn’t an issue, then I’d say go for them. They really are quite neat little machines, and all the various wheels they sell are super handy.

A flat surface looking frosted can be remedied by a quick pass on a lap wheel, the shape/size/style of which will all depend on the type of surface needing the clean-up.

Insides of the shanks can be gone at with either a mizzy wheel, a half-round file, or a sanding drum. Really just whatever is most convenient to you to remove the necessary material in the time-frame you’re after.

And finally, as far as retaining texture, ANY kind of tumbler or finisher will remove/lessen the texture to some extent. The deeper and more pronounced your texture is, however, the more it will survive the process. For example, you could sand blast a piece and throw it in a pin finisher, and end up with a near smooth piece after an hour or so. So just keep that in mind, and perhaps adjust your designs to have deeper texturing, or apply the texture after the tumbling has already been done.

Hope that all helps!
Scott

I have to disagree with the assertion that you could get a flat surface using a pin finisher. These are burnishing machines. There is no abrasive to remove material. The pins are very small and only burnish lightly. In documented tests, an entire series of finishing steps with machines on average removes 0.5% of precious metal at the most. Traditional hand finishing removes 8.0%.
If you can demonstrate such dramatic material removal, I am anxious to see it.
In my extensive testing, texture is retained far better with mass finishing than with hand finishing. My first articles on the subject were published in 2005, Lapidary Journal.