Thumler's A-R2 vs Thumler's Model B 2026
If you have a modest supply of rough and want to separate types or stages, the Thumler's A-R2 Rotary Tumbler is the better default; the Thumler's Model B Heavy Duty Tumbler suits a larger single load. The choice is two separate barrels or one large barrel, and our agate tumbler comparison can help if you want to compare more models.
Thumler's A-R2 vs Thumler's Model B
Two separate batches or one large load?
Thumler's A-R2 Rotary Tumbler
Hobbyists who want to keep two smaller rough batches or tumbling stages separate.
VS
Thumler's Model B Heavy Duty Tumbler
Hobbyists with enough rough to use one barrel that processes about 10 lb of rocks.
Barrel setup Two separate 3 lb molded-rubber barrels One metal barrel with rubber liner
Nominal barrel capacity 6 lb total across two barrels 15 lb in one barrel
Stated rock amount Usually a little under 2 lb per barrel at advised fill About 10 lb of rocks
Motor Fan-cooled and overload-protected 1550 rpm and thermally protected
Maintenance guidance Monthly oiling of motor and bearings Oil motor ports and bearings; no interval stated
Verdict
The A-R2 is the better default for modest hobby batches because its two barrels let you separate rough types or tumbling stages. Choose the Model B instead when you have enough rough to use its manufacturer-stated processing amount of about 10 lb in one barrel.
Which Thumler's tumbler fits your batches?
For most hobbyists with modest amounts of rough, the A-R2 is the more practical pick: its two barrels support separate materials or tumbling stages. The Model B is the exception to that default if you can make use of its manufacturer-stated processing amount of about 10 lb of rocks in one barrel.
What are the model-specific differences?
| Category | A-R2 | Model B |
|---|---|---|
| Barrel configuration | Two molded-rubber barrels, 3 lb nominal capacity each | One metal barrel with a rubber liner |
| Nominal barrel capacity | 6 lb total across two barrels | 15 lb for the single barrel |
| Stated rock amount | The A-R2 Q&A says each barrel usually takes a little under 2 lb of material at its advised fill level | The manufacturer says it processes about 10 lb of rocks |
| Motor | Manufacturer describes a fan-cooled, overload-protected motor | Manufacturer lists a 1550 rpm, thermally protected motor |
| Maintenance guidance | Model-specific Q&A recommends monthly oiling of motor and bearings | Manufacturer specifies oil at motor oil ports and general oil for bearings; no interval is stated on the cited page |
How do the designs change your tumbling routine?
The real difference is how you want to organize your rough, not which capacity figure looks bigger. The A-R2 gives you two separate work trays; the Model B is one deep bin for a larger load. Think about how much rough you can prepare and whether you want to keep batches apart before choosing.
Two barrels make it easier to separate batches
The A-R2 can keep different rough types or different tumbling stages in separate barrels. That helps if you want to start a second batch before the first is finished, or if you prefer not to combine materials. The two-barrel setup gives you options for organizing your work, but each barrel still needs its own proper load.
There is an important operating condition: both barrels must be mounted whenever the machine runs. If only one barrel holds rough, the A-R2 guidance says the other can be filled with water and ceramic media without grit. It also recommends filling each barrel between half and two-thirds full, usually a little under 2 lb of material. Read the A-R2 operating guidance for those model-specific loading details before setting up a run.
One large barrel suits a steady supply of rough
The Model B makes more sense if you regularly have enough rough for a larger batch and want to process it together. Its manufacturer distinguishes the barrel's 15 lb nominal capacity from the amount of rock it processes, about 10 lb. Those figures describe different things: do not plan on putting 15 lb of rocks in the barrel.
A large single load can simplify batch planning if you already have plenty of suitable rough ready. But it may be more barrel than you need if you collect only a little at a time. A bigger container does not automatically make a better first tumbler; consider what you can consistently prepare, not just what you might collect someday.
The manufacturer's Model B page also describes a metal barrel with a rubber liner, metal lid, and rubber gasket. Those construction details do not change the main buying question: can you use one larger load, or would two separate batches be more useful? The Model B manufacturer details distinguish its barrel capacity from its stated rock-processing amount.
Keep each model's oiling instructions separate
The A-R2 Q&A recommends oiling the motor and bearings monthly. That is a recurring task to include in your routine, whether you run both barrels full of rough or use one as the balancing load. The model-specific page also explains where the motor's oil ports are.
The Model B manufacturer specifies 3-in-1 motor oil at each motor oil port and general oil for the bearings, but gives no interval on that page. Do not assume the A-R2's monthly schedule applies to the Model B. Follow the instructions supplied for the exact machine you buy, and keep the oil away from the belt and pulleys.
Who should choose each model?
Choose based on the rough you can supply and whether separate batches matter to you. The A-R2 suits a split-batch routine; the Model B suits someone who can make a larger single load useful. If neither setup fits your usual amount of rough, consider a smaller-capacity tumbler instead of buying more barrel than you can fill.
Choose the A-R2 if...
Choose the A-R2 if you want separate barrels for different rough types or stages, or if a large single load would be more than you need. Its two 3 lb nominal-capacity barrels give you a way to organize smaller batches. The manufacturer includes an instruction booklet, and the model-specific loading guidance offers a concrete starting point.
Skip the A-R2 if you want to run with only one barrel mounted or would rather avoid its monthly motor and bearing oiling task. Both barrels need to be on the machine during operation, even when one holds no rough. If only one barrel contains rough, plan to use the specified water-and-ceramic-media balancing load in the other.
Choose the Model B if...
Choose the Model B if you have enough rough to use its stated processing amount of about 10 lb in one barrel. The manufacturer describes a metal barrel with a rubber liner, a metal lid, and a rubber gasket. This setup is a better fit when larger batches are part of your normal routine, not just an occasional possibility.
Skip the Model B if you mostly have small amounts to tumble or want two independent barrels for different materials or stages. Its single-barrel format does not offer that separation. You will also need to follow its own motor and bearing oiling instructions; the manufacturer lists oil locations and type, but no interval on the cited page.
If neither machine suits your supply of rough, look for a smaller-capacity option. That can be more practical than trying to keep an oversized barrel supplied, especially if you want to run batches only when you have enough material for the maker's loading guidance.
What should you confirm before choosing?
The A-R2 is the better fit for separate, modest batches; the Model B fits a larger single load. Before buying, check that the barrel arrangement suits your workflow and that you are comfortable with the exact model's loading and oiling instructions. The cards below summarize the key tradeoffs.
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FAQ
Does a 15 lb Model B barrel hold 15 lb of rocks?
No. The 15 lb figure is the Model B's nominal barrel capacity, not the amount of rocks it processes. The manufacturer separately says it processes about 10 lb of rocks. Keep the two figures distinct when planning a load or comparing tumblers.
Can the A-R2 run with only one barrel mounted?
No. The A-R2 Q&A says both barrels should be mounted whenever the machine operates. If only one holds rough, the other may be filled with water and ceramic media without grit. Do not run the tumbler with just one barrel installed.
How much rough should go in each A-R2 barrel?
The A-R2 Q&A recommends filling each barrel between half and two-thirds full. It says this usually takes a little under 2 lb of material per barrel, although the amount varies with the rough. This is model-specific guidance, not a loading rule for the Model B.
How do the A-R2 and Model B maintenance instructions differ?
The A-R2 Q&A recommends monthly oiling of its motor and bearings. The Model B manufacturer specifies 3-in-1 oil at each motor oil port and general oil for the bearings, but gives no interval on the cited page. Follow the directions for your exact model rather than transferring one schedule to the other.