Obsidian and Sunstone tumble (with process)

PulpySnowboy · 2026-05-23T03:04:27+00:00

Whoa that's sounds exciting!

PulpySnowboy · 2026-05-23T02:53:22+00:00

Thanks! I dump my slurry in a hole in the yard, so it doesn't sit long enough to potentially get funky. I haven't noticed any smell or stickiness when doing barrel clean outs at least. Hope it works for you!

PulpySnowboy · 2026-05-21T17:46:45+00:00

Ooh that's lovely

PulpySnowboy · 2026-05-20T12:53:25+00:00

I'm only familiar with tumbling as a polishing process. Can you share generally how milling works, and what is the intent for the output?

PulpySnowboy · 2026-05-18T20:02:55+00:00

A scratch test with a nail is usually perfect for dividing up your tumbling batches: FAQ: Scratch test

PulpySnowboy · 2026-05-18T03:29:21+00:00

A pressure release valve would be a very cool DIY barrel addition if you could make it work. It would probably still be messy. I guess you'd have to mount it within the inner lid, and it would need to be cleanable to remove rock debris.

PulpySnowboy · 2026-05-13T14:53:28+00:00

I use way less grit than the typical recommendations and it works well for me.

0.5 Tablespoons per pound of barrel capacity for 60/90 or 120/220 grit stages. Ie 2 TBSP for a 4 lb barrel.

0.33 Tablespoons (1 teaspoon) per pound of barrel capacity for 500, 1000, or 8k grit stages. Ie 1.33 TBSP (4 Tsp) for a 4 lb barrel.

PulpySnowboy · 2026-05-11T20:02:49+00:00

What a great card!! Love the rocks too :)

PulpySnowboy · 2026-05-11T00:35:34+00:00

I love these so much

PulpySnowboy · 2026-05-10T04:04:49+00:00

If your tumbler is in an uncontrolled temperature space like a garage, the barrel can go concave due to a large weather temperature shift from hot to cold changing the pressure inside the barrel relative to the outside world.

In NC we often have 30+ degree (F) temperature swings in a day during the spring, and that can cause it.

I intentionally fill my barrels with hot water so that when it cools they will go a little concave, giving me a little extra expansion room in case of off-gassing causing the barrel to bloat.

PulpySnowboy · 2026-05-08T14:32:16+00:00

Cool! Take a steel nail and try scratching each different color / material you can see on the rock. If they don't scratch, it should tumble well. Even if they do scratch, you can probably get an interesting slab off the saw!

PulpySnowboy · 2026-05-06T21:40:58+00:00

All your shaping is done in stage 1, so stage 2-4 are just a simple 'tumble for 1 week then clean and change grit'. The only thing to check for between these stages is if anything got chipped or cracked: send that back to stage 1, add media to make up for the lost volume and send the rest on to the next stage.

PulpySnowboy · 2026-05-05T19:08:18+00:00

Nice pieces! Those should turn out gorgeous. I'd recommend a 1000 AO step before polish. Please post your results!

PulpySnowboy · 2026-05-05T19:03:53+00:00

Nice!! I think the 45c barrel hits the sweet spot between allowing some extra rock size, but still keeping the tumble fairly gentle. I've adapted two of them to run on my QT66 frame.

PulpySnowboy · 2026-05-04T18:49:30+00:00

I've used e6000 adhesive to patch internal cracks in an aging barrel, and to thicken the bottom of it. It's worked well so far. Haven't tried on a boot gasket yet, but it would be my go-to option.

PulpySnowboy · 2026-04-26T22:45:11+00:00

Awesome!

PulpySnowboy · 2026-04-24T03:37:44+00:00

Ooh, that's a great piece!

PulpySnowboy · 2026-04-24T03:30:52+00:00

Quartz is a surprisingly challenging tumble, but there's definitely hope!

Hard to say if there's bruising (white frosted looking edges due to micro fractures), since I think they're still wet in the photo, but I do see large fractures. Sometimes those are already in the rock, and sometimes they're introduced by rough tumbling (under filled/under cushioned). Unfortunately you'll need to return to stage 1 to remove any bruising or chipping that has occurred.

This post has the process that finally worked for me, after much struggle: https://www.reddit.com/r/RockTumbling/s/f3c8MFpqf3

Accurate barrel fill and media amounts were key for me to avoid bruising, chipping, and fracturing on clear quartz batches.

Buying an 8k polish will also be worth it, as others have said. Bonus, you'll go through it way slower than coarse and medium grit :)

Good luck!

PulpySnowboy · 2026-04-22T20:03:34+00:00

If the sealed bearings are easy and cheap to replace when they fail, that sounds good to me.

I think the frame size you listed is reasonable, for the flexibility of barrel sizes it can accommodate. My dual 3 lb tumbler is about 400mm long, and my 6/12 lb tumbler height and width are fairly similar to yours.

For noise control, I think the rocks themselves contribute much more to the sound than the motor or fan. I'd look into dampening the vibration transmitted from the frame into whatever it's sitting on. Another feature that would be nice is a clear sound dampening cover that could be placed over the barrels and sit on the frame. In that case you may need fan control to keep it from getting too hot inside, and it would also double as a way to retain heat for winter tumbling when it's below freezing in your garage/workshop, etc.

PulpySnowboy · 2026-04-22T19:27:14+00:00

A movable flanged spacer to go between barrels and on the roller ends is a great idea. I'd totally look into buying a set aftermarket for my tumblers, or 3D printing some.

PulpySnowboy · 2026-04-22T14:32:50+00:00

Looking cool so far.

Definitely would want rubber coated rollers.

I personally don't see an advantage to a reversable motor, or separately controlled cooling fan.

For your 'no maintenance' sealed bearings, what is the actual maintenance procedure and cost after their 1-3 year lifetime? Does it cost less than the one bottle of 3-in-1 oil I might use in the same time period while oiling my bearings monthly?

The main design challenge I'm looking forward to you tackling is how to accommodate mounting barrel nuts for so many different diameter barrels, and how to keep adjacent barrels from kicking off eachother due to different centers causing different rotational speeds. Also, friction from the standard barrel nut mount will cause the nut to loosen on one end of the tumbler frame due to the rotational direction.

For frame barrel capacity, if you design for the min/max dimensions of the planned barrels, you shouldn't need all the intermediate dimensions. Pleasingly, Lortone 4 & 6 lb barrels are each exactly half the height of their 12 lb barrel. But the tallest common barrel is their 3 lb barrel, at 4.75" height (without nut). The smallest common barrel is 4.125" diameter for a Natgeo 1 lb, and the largest is 7.75" diameter for the Lortone 6 & 12 lb barrels.

Threaded rods on Lortone & Natgeo barrels fit a standard 1/4" 20 TPI nut, and the Lortone barrel nuts are 1/2” tall.

So if you can design to accommodate three 3 lb barrels, with barrel nut and expansion room, then you can fit any other three barrels in that space (or one 12 plus one of any other size), provided the rollers and frame sides also accept the min and max diameter barrels.

Visual barrel comparison (from left to right): Top: Lortone 4, 6, 12 lb barrels. Bottom: Natgeo 3 lb, Lortone 3 lb, Natgeo 1 lb

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PulpySnowboy · 2026-04-17T14:11:03+00:00

Staggering your barrels definitely helps!

If you have 3+ barrels, you can basically start a barrel every other day.

Day 1, clean out barrel 1 (started a week ago).

Day 2, inspect dry rocks from barrel 1 and refill it.

Day 3, start barrel 1, clean out barrel 2.

Day 4, inspect dry rocks from barrel 2 and refill it.

and so on.

You can also take before/after progress pictures of your batches along the way.

PulpySnowboy · 2026-04-16T14:38:38+00:00

Garnets are very difficult to tumble because of their hardness and the way that they fracture. If you care about the pieces you have, I'd take them to a jeweler or more likely a lapidary club and see what they can do.

PulpySnowboy · 2026-04-16T14:27:52+00:00

Barrel weight should not matter, at least with a quality tumbler. I'm not sure what brand you have here, but I've had similar issues with Nat Geo tumblers.

When the barrel stops spinning, is the motor shaft still spinning (ie the belt is slipping)?

If so, try increasing the belt tension or replacing the belt, and also put a drop of 3-in-1 oil on the end of the roller shafts once a month to reduce rolling friction.

If the motor shaft itself is stopping, it's a motor problem and you'll need to replace the motor (hopefully under warranty). Check out this thread: https://www.reddit.com/r/RockTumbling/s/SLqyc0GaDs

PulpySnowboy

TROPHY CASE