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

Jewelry Discussion
#1

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?

#2

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

#3

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.

#4

In my experience the magnetic pin tumbler will leave minute dents on the surface of the piece. If you want textured rings (depending on the texture you are trying to obtain) magnetic tumbler could work. Yes, the magnetic tumbler will leave a “frosted” surface. If you want the surface smooth and bright you would need to use sand paper and then polish it ( on the inside of the shank)
The magnetic tumbler will burnish the surface while leaving (minute dents/texture) it will leave the piece bright and shiny. It will not give you a clean, finished smooth surface. If you if want a smooth surface on certain parts of the rings you will need to polish it afterwards.

#5

If, in addition to a magnetic pin finisher, you also have a rotary tumbler that can handle steel shot, you can follow the pin finisher with a run in standard steel shot. That stuff is heavier, and burnished deeper. It will remove that pebbled finish from the magnetic tumbler. With some softer metals like silver, the pieces may need only a light polish. The combination of the two types if tumbler is that all of the more exposed surfaces get the burnished steel shot finish, but the more recessed areas get the slightly rougher magnetic pin finisher, which are harder to reach, but totally adequate for small mostly hidden surfaces. The steel shot also compresses the surface, leading to a slightly harder surface with few if any pits or porosity still visible, and when you follow that with conventional light buffing, you’ll get a higher polish too.

#6

I’m not sure why you are getting small dings in the surface of your metal. I use a mag finisher on fine silver and sterling silver and have never gotten those dings. Of course, I don’t aim for a mirror finish on my work and, if I were doing so, I might experience those blemishes. No way to tell. If you are aiming for that kind of surface, Peter Rowe’s suggestion seems likely to solver your problem.

#7

When I first learned to make jewelry almost 50 years ago, I was taught to file or grind as needed, sand, and then polish with tripoli and then red rouge on large sewn treated cloth wheels driven by at least a 1/2 HP motor. I was able to produce a very high polish with no firescale other than in the very recessed areas. This finish has always been my standard, regardless of what kind of texture I add after it is polished. If you skip it, then all the blemishes will show through your texture. Fast forward a few years and I was doing a lot of shows polishing into the night. I decided to see if the new vibratory tumblers and various ceramic and plastic media that had become available might not speed up my polishing. Along with treated sawdust and corncobs I was able to get a decent finish on the smaller pieces that were my bread and butter at show, but my larger pieces with wide flat areas still needed to spend some time on the wheel. Fast forward another fifteen years. I am no longer doing shows and everything gets polished on the wheel as I can do it faster than waiting for the tumbler to get to the point where I still have to do touch up on the wheel anyway. I did buy a 6 quart rotary tumbler for stainless steel shot and I can go from grinding to sanding to SS shot and get a decent finish on smaller pieces that are hard to hold on to like ear wires and small stud earrings. I also bought two smaller vibratory tumblers and can run ceramic in one, plastic in the other and treated sawdust in the original tumbler. I now use various combinations per JudyH’s book and good advice, but most pieces still spend time on the wheel to get the finish that became my standard years ago. Filing and sanding have, for the most part, been replaced with rubber abrasive wheels on my flexshaft and I would like to try some of the Jool Tool wheels sometime. I have been tempted to buy a pin finisher, actually, I am more tempted to build my own, but my research says that it isn’t the miracle cure for having to spend a lot of time on the wheel. My polishing hood is the one I originally built years ago with lots of modifications. It is well ventilated and well lit with LEDs and a foot switch that will shut down if something happens. I spend more time finishing than making most pieces. It’s just a part of the process and, for me, the most important. Don will tell a similar story because we were taught by the same person. Good luck…Rob