Building a magnetic polisher. Stage 3: the test

[PeteJ]

Be interesting to see how this works. One difference I noticed, and of course it to late to change it at this point, but the magnets in mine are bar magnets. I don't know if it matters, but I would think that would keep the pins spread out a bit more evenly. An alternative might be to stager the location of you magnet relative to the center. With them spinning in the same circle, you may get an uneven distribution of polishing medium. Just a thought.

[MoFo]

It's a little hard to see in the pics, but the magnets are staggered. There's about 1/2" overlap between the two magnets, so there's 1 1/2" coverage overall.

Interesting to know the production units use bar magnets. They'd be trickier to install with this set-up, though (getting into routers or dadoes). If I need more coverage, I'll probably go with pairs of round magnets in tandem instead.

[MoFo]

Had a .

I needed something to support the bowl. Some kind of platform, thin and rigid in the middle, with long legs. Really, just a frame to hold some rigid material to put the bowl on. Some... frame.

So, quick trip to Wal Mart later and I've snagged a $7 picture frame. The frame is robust enough to screw on some wooden legs. The glass is strong enough to support a bowl, but thin enough to minimize distance to the magnets.

Bit of measuring. Bit of cutting. Bit of drilling and screwing. I've added some bolts to the wooden legs to make it height adjustable - I can level out the platform, and raise it off the magnets or lower it closer as needed. Tossed a dollop of burnishing soap, the pins and some water in my bowl and I'm running them through to clean off any residue.

IT WORKS!

And I'm at fairly low power still, too. Plenty of room to crank it up. I'll have to do some playing around to figure out how many pins to use and what speeds work best, but... IT WORKS!

Running the pins through a few cleaning cycles as I type, before throwing in some test parts.

[PeteJ]

I am not sure if it has been mentioned yet but here are some instructions that I picked up. Never leave the pins sitting on the magnets. They need to not be magnetized to work properly. Change the water and solution each time you use it. This pins work like little hammers not an abrasive. They are basically penning the surface not scraping it, so keeping the pins in good shape is important. They do wear out.

[MoFo]

Bump for Mr. Grumpy. Also, a few thoughts, comments and final remarks...

I'm using both .5mm pins bought from a local jewellery supply store ($22/100g), and some .3mm pins bought off eBay ($20/220g). I also bought some tumbling soap from the same eBay seller, and some burnishing liquid from the jewellery store. These were far and away the single biggest expense in putting the unit together.

My initial results with the soap and .3mm pins weren't great. Probably a lot of factors, but running a load of just straight pins generated a lot of smut. I'd read that you want to run new pins for a load or two until the water remained clear; I did probably half a dozen loads and they were absolutely filthy. Switching to the burnishing liquid improved things markedly - a single cycle cleaned them, and now they even LOOK shinier. So, proper burnishing fluid is a must!

For 1/43, I'd say the .3mm are an unfortunate necessity; in 1/20, you'd probably use .5mm *most* of the time, but the .3mm's would come in handy for some parts; for 1/12 kits, you could probably get away with using the .5mm pins exclusively.

When it comes to the pins, less is more. I started out dumping in the whole 220g to try to clean them. Waaaaay too many pins! Right now, I've probably got less than 50g, and it's probably still too much.

I'm still playing with speeds and times, but running a 15 minute-ish cycle at about half power (around 1250rpm) seems to be about right. For parts with finer detail, I've been using the .3mm pins and bumping up the time; for less detailed parts, .5mm and a little less time. One thing I have noticed: as you run the tumbler, the water turns black from the tiny metal particles generated; if you KEEP running while the water is black, it seems to burnish this into the surface, giving a dark, anodized look.

You have to be super, super careful to avoid magnetizing the pins. Mine seem to have become slightly magnetized over just a few cycles. Not really sure why - I've never left them on the machine. Wondering if a magnetizer/demagnetizer might help... though they still seem to work fine.

The single worst part of tumbling is trying to pick out all the tiny little 1/43 parts after you're done. With the .3mm pins, it's a bit of a nightmare; with .5mm it's less awful. I'd hoped to use a magnet to pull all the pins to one side of the bowl, but the smaller white metal parts just get pulled along with them. I'm thinking my best bet is probably some sort of fine colander - shake the pins out, into a container underneath, while hopefully trapping the parts. In the mean time...

Photograph everything that goes into the tumbler, so you can make sure it comes back out. I'm just paranoid that way.

All in all, though, I'm really, really happy with the results. You kind of have to hold a tumbled part in your own hands to realize how big a difference it makes, and how completely impossible it would be to get those results manually. And as I said above, all-in I'm at about 1/3 the price of a base model tumbler from a retailer, with a larger, more flexible unit (and I'm more than $1000 under the price of a similarly sized commercial unit). That's a lot kits.

[Mr.Grumpy]

wow, impressive. i have to tell you though, i actually laughed out loud when i saw your lathe mounted upright on your wall. the things we do for our hobby huh?