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A large rock tumbler makes sense when your rough arrives by the bucket. A 3 lb barrel handles about 2 lb of rock a month; a 15 lb machine handles about 10 lb in the same time, and it takes the 2 and 3 inch stones that small barrels can't. That's why rock shops, schools and serious collectors run big machines.
Big barrels change the economics, though. Grit use scales with barrel size, the machines are heavy and permanent, and a half-empty large barrel tumbles badly. The key questions are real rock capacity (not the label), barrel material, barrel speed, and how much rough you actually have. Every capacity and motor detail below comes from the manufacturer's page, its manual, or the retail listing.
Quick Picks
- Best Overall: Thumler's Tumbler Model B. Best for about 10 lb of rock per batch in a rubber-lined steel barrel.
- Best Rubber Barrel: Thumler's Tumbler A-R12. Best for a quieter 12 lb rubber barrel with a continuous-duty motor.
- Best Lortone: Lortone QT12. Best for Lortone fans who want one 12 lb barrel and published grit doses.
- Best Large Twin: Lortone QT-66. Best for two 6 lb batches at once.
- Best Value Big Barrel: Rebel 17 Rock Tumbler. Best for a 17 lb rubber-lined drum at a lower tier than the legacy brands.
- Largest Capacity: KomeStone G3 22LB. Best for the biggest barrel here, with a brushless motor and a 5-year warranty.
Large Rock Tumbler Comparison Table
| Tumbler | Best for | Barrel | Rated capacity | Real rock per load | Motor / speed |
|---|---|---|---|---|---|
| Thumler's Model B | Overall | Steel, 1/4 in rubber liner | 15 lb | About 10 lb (Thumler's) | 1550 rpm thermally protected motor; about 20 barrel rpm (Rocktumbler.com) |
| Thumler's A-R12 | Rubber barrel | Hexagon rubber | 12 lb | About 6 to 8 lb at 1/2 to 2/3 fill | Fan-cooled, continuous duty, overload protection; about 22 barrel rpm (Rocktumbler.com) |
| Lortone QT12 | Lortone | Rubber | 12 lb | About 6 to 8 lb | V-belt drive |
| Lortone QT-66 | Large twin | 2 molded rubber | 2 x 6 lb | About 3 to 4 lb per barrel | Continuous-use motor |
| Rebel 17 | Value | Stainless, removable rubber liner | 17 lb | Not stated | 115V 1/30 HP fan-cooled, overload protection; 20 rpm |
| KomeStone G3 | Largest | Metal-clad drum | 22 lb | Not stated | Brushless; about 40 to 50 rpm |
Real rock per load for the Lortone and Thumler's A-R12 barrels uses Lortone's half-to-two-thirds fill rule; makers don't publish a figure.
The Best Large Rock Tumblers, Reviewed
Thumler's Tumbler Model B: Best Overall
Who it's for: rockhounds, clubs, schools and small sellers processing 10 lb of rock at a time.
The Model B is the machine you see in rock shops. Thumler's builds it around a steel barrel with a 1/4 inch rubber liner and a gasketed lid, rates it at 15 lb, and says it processes about 10 lb of rock per load. It's made in the USA, and Thumler's lists a one-year limited warranty.
Order the right motor. Thumler's sells the Model B with a 1550 rpm thermally protected motor for rock tumbling and a 3000 rpm high-speed version aimed at metal deburring. For rocks, choose 1550. Rocktumbler.com, a Thumler's dealer, puts the Model B's barrel speed at about 20 revolutions per minute, slow enough that it lists the Model B as suitable for glass.
Stone size is where it shines. Rocktumbler.com recommends 1-1/2 to 3 inch rocks in the Model B and has tumbled 3 to 4 inch "monster" pieces in it, a few at a time.
Pros
- About 10 lb of rock per batch
- Rubber-lined steel barrel takes 1-1/2 to 3 in stones
- Thermally protected, US-made motor
- Slow barrel speed is gentle on fragile material
Cons
- Easy to order the 3000 rpm metal version by mistake
- Louder and heavier than rubber barrels
- High grit cost per batch
Thumler's Tumbler Model B Heavy Duty 15 lb Rock Tumbler
by Thumler's Tumbler
Thumler's Tumbler A-R12: Best Rubber Barrel
Who it's for: hobbyists who want a big batch without a steel barrel's noise.
The A-R12 scales up Thumler's A-series design. Thumler's lists a 12 lb hexagon rubber barrel on a fan-cooled, continuous-duty motor with overload protection, made in the USA, and describes it as quiet. The hexagon shape helps lift the load so it tumbles rather than slides.
Rocktumbler.com puts its barrel speed at about 22 rpm, and recommends the same 1-1/2 to 3 inch rough as the Model B. Rubber is quieter than steel, which makes the A-R12 a better fit for a basement or attached garage.
At Lortone's half-to-two-thirds fill rule, plan on roughly 6 to 8 lb of rock. Thumler's doesn't publish a rock-per-load figure or a warranty term on the A-R12 page.
Pros
- 12 lb rubber barrel is quieter than steel
- Continuous-duty, overload-protected motor
- Made in the USA
- Shares belts and parts lineage with the A-R series
Cons
- Smaller real capacity than the Model B
- Warranty terms not stated on the product page
- Needs plenty of rough to fill
Thumler's Tumbler A-R12 Rock Tumbler
by Thumler's Tumbler
Lortone QT12: Best Lortone
Who it's for: Lortone owners moving up, and anyone with lots of one material.
The QT12 runs a single 12 lb rubber barrel on a V-belt drive. Its biggest advantage is Lortone's documentation: the chart calls for 20 level tablespoons of each grinding grit and 24 of each polish in a 12 lb barrel, and the usual Lortone method applies. Fill half to two-thirds full, check after 2 to 3 days, and expect each stage to finish in 5 to 7 days.
A single big barrel suits one material at a time, such as a haul of agate or jasper. You'll need roughly 6 to 8 lb of rough per batch, plus extra to replace culls.
Pros
- 12 lb rubber barrel, quieter than steel
- V-belt drive
- Precise grit doses in Lortone's chart
- Simple, low-maintenance Lortone design
Cons
- One material and one stage at a time
- High grit use per batch
- Large footprint
Lortone QT12 Rotary Rock Tumbler
by Lortone
Amazon availability: the Lortone QT12 showed as currently unavailable on Amazon.com when we checked in October 2026, and Lortone sells mainly through lapidary dealers. If you'd rather order on Amazon, the Thumler's Tumbler Model B is the closest big single-barrel match: a 15 lb steel barrel with a rubber liner that processes about 10 lb per run. It's reviewed on this page.
Lortone QT-66: Best Large Twin
Who it's for: hobbyists who want large-barrel volume but more than one batch going.
The QT-66 offers the same 12 lb of total capacity as the QT12, split into two 6 lb molded rubber barrels. That's the more flexible way to use 12 lb. You can grind one batch while polishing another, or keep a softer material in its own barrel. Lortone's chart calls for 10 tablespoons of each grinding grit and 12 of each polish per 6 lb barrel.
Each barrel holds about 3 to 4 lb of rock at the recommended fill. If you want two batches and big stones but don't need a 12 lb load of one material, this is the better buy. Our upcoming double barrel rock tumbler guide compares other twins.
Pros
- Two 6 lb barrels, 12 lb total
- Run two stages or two hardness groups at once
- Larger stones than 3 lb barrels
- Lortone's published grit chart
Cons
- Smaller per-barrel load than the QT12
- Big, heavy frame
- Two barrels of grit to buy
Lortone QT-66 Rotary Rock Tumbler
by Lortone
Rebel 17 Rock Tumbler for Adults: Best Value Big Barrel
Who it's for: buyers who want a big rubber-lined drum without paying Thumler's prices.
Extreme Tumblers' Rebel 17 has a 17 lb stainless steel drum with a thick, removable rubber liner that turns at 20 rpm, the same slow speed Rocktumbler.com gives for Thumler's Model B. The listing calls out a 115V, 1/30 HP fan-cooled motor with overload protection, heavy-duty rods and ball bearings, and a powder-coated base. Extreme Tumblers backs the barrel and liner for 3 years and the motor for 1 year.
One buying note: Extreme Tumblers also sells a Rebel 17 for brass cartridge cleaning that turns at about 40 rpm. For rocks, choose the rock tumbler version at 20 rpm.
The Rebel 17 has less long-term history in rock tumbling than Thumler's or Lortone, and the listing doesn't say how much rock it processes per load. Plan on Lortone's half-to-two-thirds rule.
Pros
- 17 lb rubber-lined stainless drum
- Slow 20 rpm barrel speed
- Fan-cooled, overload-protected motor
- 3-year barrel and liner warranty
Cons
- Brass-cleaning version is easy to confuse with it
- Rock-per-load figure not published
- Shorter rock-tumbling track record
Rebel 17 Rock Tumbler for Adults
by Extreme Tumblers
KomeStone G3 22LB Professional Heavy-Duty Large Rock Tumbler: Largest Capacity
Who it's for: high-volume tumblers who want the biggest barrel and modern controls.
The G3 is the largest machine here. KomeStone lists a 22 lb barrel sealed by six metal twist knobs, a metal base and metal-clad drum shell, and a brushless motor turning the barrel at about 40 to 50 rpm (about 48 rpm at two-thirds full). A three-screen display shows total days, extra hours and live power use, and KomeStone says typical daily energy use stays under 0.5 kWh. Its 5-year warranty covers motor replacement, and KomeStone sells belts, barrels, lids and the base as parts.
That barrel speed is noticeably faster than the 20 to 22 rpm of Thumler's big machines. That's fine for agate and jasper, but Rocktumbler.com says glass and fragile stones do best under about 50 to 60 rpm, so stay toward the low end and use plenty of media with soft material.
AtoRock's A3 is a close alternative, with a 22 lb barrel, brushless motor, run-time and wattage display, and a 5-year warranty listed.
Pros
- 22 lb barrel, the largest here
- Brushless motor and 5-year warranty
- Run-time and power display
- Replacement parts sold
Cons
- Faster barrel speed than Thumler's big machines
- Rock-per-load figure not published
- Newer brand with less long-term history
KomeStone G3 22LB Professional Heavy-Duty Large Rock Tumbler
by KomeStone
Buying Guide: Choosing a Large Rock Tumbler
Rated Capacity vs Real Rock Load
Barrel ratings describe the barrel, not the rock. Lortone tells you to fill a barrel half to two-thirds full of rock; Kingsley North and Harbor Freight allow up to three-quarters. Thumler's is the one maker that publishes a real figure: its 15 lb Model B processes about 10 lb. A good rule is two-thirds of the rating.
| Rated barrel | Approximate rock per load |
|---|---|
| 6 lb | 3 to 4 lb |
| 12 lb | 6 to 8 lb |
| 15 lb | About 10 lb (Thumler's) |
| 17 to 22 lb | About 11 to 15 lb (two-thirds rule) |
Do You Have Enough Rough?
An underfilled big barrel tumbles poorly: stones slam into each other and chip. Before buying, check your supply. If you have less than 6 lb of one hardness group at a time, a twin like the Lortone QT-66 or a 3 lb twin is a better fit. Ceramic media can top up a short load; see our ceramic media guide. For buying rough in bulk, see our rough stones for tumbling guide.
Grit Cost Scales With the Barrel
Lortone's chart, in level tablespoons:
| Barrel | 60/90 | 120/220 | Pre-polish | Polish |
|---|---|---|---|---|
| 6 lb | 10 | 10 | 12 | 12 |
| 12 lb | 20 | 20 | 24 | 24 |
That's five times the 3 lb dose in a 12 lb barrel. Rocktumbler.com's rule of about 2 tablespoons per pound of rock gives similar totals. Buy grit in bulk; our rock tumbler grit guide compares kits by rock capacity.
For very angular rough, Rocktumbler.com sells 46/70 extra coarse grit and recommends it only for barrels of 6 lb or more. Big barrels are where it pays off.
Stone Size and Barrel Speed
Big barrels take big stones. Rocktumbler.com recommends 1-1/2 to 3 inches for Thumler's A-R12 and Model B, with small pieces mixed in, and nothing larger than about half the barrel diameter.
Barrel speed matters for fragile material. Rocktumbler.com gives about 20 rpm for the Model B and 22 for the A-R12, and says glass tumbles well under about 50 to 60 rpm. Slower big barrels give a long, gentle cascade. Faster ones grind quicker but bruise soft stones more readily.
Timing by Hardness
Large barrels follow the same schedules as small ones. Lortone calls for 5 to 7 days per stage, Harbor Freight 7 to 10 days of coarse, and Kingsley North says to repeat coarse until stones are evenly rounded. Rocktumbler.com notes that its coarse stage on beach stones takes about a week or more in a large rotary and longer in small ones; bigger barrels give stones a longer drop.
Hardness still sets the pace. For stones softer than Mohs 7, Rocktumbler.com suggests about 1-1/2 fewer coarse days per Mohs point. In a big barrel, that matters even more, because a large batch of soft stone can lose a lot of size in a few extra days. Our rock tumbling timeline calculator adjusts for hardness.
Steel vs Rubber Barrels
Steel barrels with rubber liners (Thumler's Model B, Rebel 17) are tough and take big stones, but they're louder. All-rubber barrels (Thumler's A-R12, Lortone QT12 and QT-66) are quieter. Either way, a large tumbler belongs in a garage, basement or workshop on a level surface you can wipe down.
Weight, Space and Slurry
Large machines are heavy once loaded. The Rebel 17 alone weighs 17 lb before any rock, and the KomeStone G3 is listed at 24 lb. Plan a permanent spot. You'll also produce a lot of slurry. Never pour it down a drain: Lortone warns against it, and Kingsley North notes that slurry settles and hardens in pipes. Let it settle in buckets and bin it.
"Industrial" and "Commercial" Labels
There's no standard behind these words. Look for what actually matters: a motor its maker rates as continuous-duty or thermally or overload protected, a metal frame, a replaceable barrel liner or barrel, and available parts. Lortone's C20 and C40 are its commercial-scale machines, beyond most home setups. For general picks, see our best rock tumbler roundup and our guide to rock tumblers for adults.
How We Chose
We didn't test these tumblers ourselves. We researched them. We read Thumler's product pages, Lortone's manuals and grit charts, Rocktumbler.com's barrel-speed and stone-size guidance, and the retail listings for the Rebel 17 and KomeStone G3. We weighed real rock capacity, barrel material, motor protection and parts support, and we flagged where makers don't publish rock-per-load figures or warranty terms.
FAQ
What is the biggest rock tumbler for home use?
Among hobby machines sold to consumers, 15 to 22 lb barrels are the top end. Thumler's Model B is rated at 15 lb and processes about 10 lb of rock, the Rebel 17 has a 17 lb drum, and KomeStone and AtoRock sell 22 lb models. Lortone also makes larger commercial machines, the C20 and C40, which are beyond most home setups.
How much rock goes in a 12 lb or 15 lb tumbler?
Less than the rating. Lortone says to fill a barrel half to two-thirds full of rock, and Thumler's says its 15 lb Model B processes about 10 lb. Expect about 6 to 8 lb of rock in a 12 lb barrel and about 10 lb in a 15 lb barrel.
How much grit does a large rock tumbler use?
A lot. Lortone's chart calls for 20 level tablespoons of each grinding grit and 24 of each polish in a 12 lb barrel, five times the 3 lb dose. Rocktumbler.com's rule of about 2 tablespoons per pound of rock gives similar numbers. Budget for bulk grit.
Do large rock tumblers take longer?
Not per stage. The same one-week-per-stage schedule in Lortone, Harbor Freight and Kingsley North manuals applies, and Rocktumbler.com reports coarse grinding taking about a week or more in a large rotary and longer in small ones. Hardness still sets the pace: softer stones need shorter coarse runs.
What makes a rock tumbler industrial or commercial?
There's no formal standard. In practice the term describes a large barrel, a metal frame and a motor rated for continuous duty, often with thermal or overload protection. Thumler's Model B is common in rock shops and schools, and Lortone's C20 and C40 are its commercial-scale machines.
Verdict
The Thumler's Tumbler Model B is the best large rock tumbler for most people: about 10 lb of rock per batch, a rubber-lined steel barrel and a protected, US-made motor. Choose the A-R12 or Lortone QT12 if you want a quieter rubber barrel, and the QT-66 if two batches matter more than one big one. The Rebel 17 and KomeStone G3 are the picks if you want more capacity for the money.