The Thumler’s Tumbler A-R12 is a heavy-duty, 12-pound-capacity rotary rock tumbler designed for serious rock tumbling, polishing, and other demanding tumbling applications. Its large hexagonal rubber barrel, durable metal base, and continuous-duty motor make it an excellent choice for lapidaries who want more capacity than a small hobby tumbler without moving up to the larger Model B.
The A-R12 is built for quiet, efficient operation and is well suited for polishing rocks and minerals as well as other applications such as cleaning and polishing brass cartridge cases.
Large 12-Pound Capacity
The A-R12 features a large 12-pound-capacity hexagonal rubber barrel, giving you substantially more capacity than smaller single- or dual-barrel tumblers.
For rock tumbling, the 12-pound rating refers to the barrel's overall tumbling capacity. As with any rotary tumbler, the actual amount of rough rock you can process depends on the size and density of the material, the amount of tumbling media being used, and the need to maintain proper barrel loading.
A properly loaded barrel allows the rocks, media, water, and abrasive to roll together efficiently throughout the tumbling cycle.
Hexagonal Rubber Barrel
The A-R12 uses a durable hexagonal rubber barrel designed specifically for rotary tumbling.
The barrel's hexagonal shape helps lift and drop the material as it rotates, creating the rolling action necessary to grind and polish the stones. The rubber construction also helps reduce noise and cushions the rocks as they tumble.
The barrel has an approximately 7-3/8" usable interior height and 5-3/4" interior diameter. Outside dimensions are approximately 8-1/4" high × 8-5/16" diameter.
The A-R12 barrel includes a hard plastic lid and retaining hardware to help create a secure seal during tumbling.
Quiet, Efficient Rock Tumbling
Rubber barrels are significantly quieter than bare metal barrels, making the A-R12 a good choice for home workshops, garages, hobby rooms, and lapidary studios.
The barrel's internal hexagonal shape promotes consistent movement of the load while the rubber construction helps reduce the sound produced as the stones tumble.
For rock tumbling, the A-R12 is designed for the long running times required to move rough material through the coarse, medium, fine, and polishing stages.
Fan-Cooled Continuous-Duty Motor
The A-R12 is equipped with a fan-cooled, continuous-duty motor designed for extended operation.
The A-R series motor is rated at:
- 115 volts
- 0.45 amps
- 60 Hz
- 1,550 RPM
The motor is also equipped with overload protection, helping protect the motor if the tumbler is subjected to excessive load or operating conditions.
The fan-cooled design helps dissipate heat during extended tumbling cycles, which is particularly important because rock tumbling commonly requires machines to run continuously for days at a time.
Heavy-Duty Metal Base
The A-R12 is built on a durable metal base designed to support the weight and vibration produced by a fully loaded 12-pound barrel.
The drive shaft and idler shaft are supported by the base and fitted with rollers that allow the barrel to rotate smoothly during operation.
The A-R12's straightforward mechanical design also makes routine maintenance and replacement of wear components relatively simple. Thumler’s continues to offer replacement barrels, lids, shafts, rollers, belts, motors, clamps, and other parts for the A-R12.
Ideal for Rock Tumbling
The A-R12 is an excellent choice for anyone who wants a substantial rotary tumbler for processing larger quantities of material.
Ideal for:
- Rock and mineral tumbling
- Agate and jasper
- Quartz and other hard stones
- Petrified wood
- Rough stone smoothing and polishing
- Pre-polishing cabochon material
- Cleaning and polishing brass cartridge cases
- Other small-part tumbling applications
The A-R12 is particularly well suited to serious hobbyists and lapidaries who want a durable machine capable of running extended tumbling cycles.
Built for Long-Term Use
One of the advantages of the A-R12 is its serviceable mechanical design. Thumler’s continues to offer replacement components for the machine, including the barrel, barrel lid, retaining clamp, drive shaft, idler shaft, rollers, belt, motor, and base components.
That means the A-R12 isn't designed as a disposable hobby appliance. Individual wear components can be replaced as necessary, allowing the machine to remain in service for many years.
A-R12 vs. Smaller Tumblers
If you're deciding between the A-R12 and a smaller tumbler, the biggest difference is capacity.
A smaller tumbler may be easier to load and is perfectly suitable for someone processing small quantities of material. The A-R12 gives you a substantially larger single barrel, making it more practical when you want to process larger batches without running multiple small barrels.
The A-R12 is also a good middle ground between smaller Thumler's models and the larger 15-pound Model B.
Product Specifications
Brand: Thumler’s Tumbler
Model: A-R12
Type: Rotary Rock Tumbler
Manufacturer: Thumler's Tumblers SKU: THU130
Capacity: 12 lb
Barrel Type: Hexagonal rubber barrel
Barrel Construction: Rubber
Barrel Lid: Hard plastic
Barrel Retention: Metal retaining clamp
Usable Barrel Interior: Approx. 7-3/8" H × 5-3/4" diameter
Outside Barrel Dimensions: Approx. 8-1/4" H × 8-5/16" diameter
Motor: Fan-cooled, continuous-duty
Motor Speed: 1,550 RPM
Motor Voltage: 115V
Motor Current: 0.45A
Frequency: 60 Hz
Motor Protection: Overload protection
Base: Heavy-duty metal
Primary Application: Rock tumbling and polishing
Additional Applications: Brass and small-part tumbling
Country of Manufacture: USA
What You Need to Get Started
If you're purchasing the A-R12 for rock tumbling, you'll need more than just the tumbler itself.
A basic setup includes:
- A-R12 Rock Tumbler
- Suitable rough rock
- Coarse silicon carbide grit
- Medium silicon carbide grit
- Fine silicon carbide grit
- Pre-polish
- Rock polishing compound
- Tumbling media, when needed
- Water
- Containers for cleaning and separating the different stages
The exact grit and polish sequence depends on the type and hardness of the material you're tumbling. Hard stones such as agate, jasper, and quartz generally require a different approach than softer materials.
If you're new to rock tumbling, choosing the right grit and polish is just as important as choosing the tumbler itself.
Serious Capacity Without Going Oversized
The Thumler’s Tumbler A-R12 offers a combination of large capacity, quiet operation, durable construction, and serviceable components that makes it a strong fit for serious lapidary work.
Its 12-pound rubber barrel provides plenty of capacity for larger batches of rough, while the fan-cooled continuous-duty motor is designed for the extended operating times required for rock tumbling.
Whether you're polishing agate and jasper, processing petrified wood, or looking for a dependable tumbler for regular lapidary work, the A-R12 provides the capacity and construction needed to keep up with repeated tumbling cycles.
Thumler’s Tumbler A-R12 — a durable 12-pound rotary tumbler built for serious rock tumbling and long-term lapidary use.
