The Thumler's Model B Rock Tumbler is a heavy-duty, commercial-grade rotary tumbler designed for serious rock tumbling and polishing. With its large 15-pound-capacity barrel, powerful thermally protected motor, steel construction, and thick rubber barrel liner, the Model B is built for tumbling larger batches of rocks and running the extended cycles required to produce beautifully polished stones.
Made in the USA, the Model B combines a rugged metal frame and barrel with a removable rubber liner that provides quiet operation while protecting your stones and the barrel itself.
If you're looking for a tumbler that can handle significantly more material than typical hobby-size machines, the Model B is an excellent choice for experienced rock tumblers, families, clubs, and anyone who regularly processes larger batches of rough.
Why Choose the Thumler's Model B?
- Large 15 lb. Barrel Capacity – Process substantially larger batches than small hobby tumblers.
- Heavy-Duty, Commercial-Grade Construction – Built with a sturdy metal base and steel barrel for years of dependable use.
- 1550 RPM Thermally Protected Motor – The low-speed motor is designed specifically for rotary rock tumbling and includes thermal protection to help prevent overheating.
- Thick Rubber Barrel Liner – The approximately 1/4" thick rubber liner reduces noise and provides a durable tumbling surface.
- Watertight Barrel Seal – A rubber gasket between the liner and metal lid helps create a tight seal for wet tumbling.
- Hexagonal Barrel Design – The polygonal interior provides excellent tumbling action as rocks continuously lift and fall during rotation.
- Easy Barrel Access – The metal lid is secured with six washers and wing nuts and can be removed for convenient loading and cleaning.
- Serviceable Design – Individual components such as the motor, pulley, belt, shafts, barrel liner, gasket, and lid are available as replacement parts.
- Powder-Coated Finish – The painted metal surfaces are designed to resist chipping and rusting.
- Made in the USA – A rugged, long-standing tumbler design manufactured in the United States.
Large 15-Pound Capacity
The Model B features a 15-pound-capacity barrel, making it one of the larger rotary rock tumblers available for hobby and small-scale production use.
The 15-pound figure refers to the barrel's overall capacity. For rock tumbling, Thumler's indicates that the machine can process about 10 pounds of rocks, with the remaining space and weight used by water, abrasive, and tumbling media as appropriate.
This larger capacity makes the Model B especially useful if you:
- Want to tumble larger quantities of rocks at once
- Regularly collect and process your own rough material
- Want to tumble larger pieces that won't fit comfortably in small barrels
- Need more capacity for family or club projects
- Prefer to run fewer, larger batches instead of many small batches
For the best results, the barrel should be loaded appropriately rather than simply filled with rocks. Proper loading allows the rocks, abrasive, water, and media to move together during the tumbling process.
Heavy-Duty Metal Barrel
The Model B uses a steel hexagonal barrel with a removable rubber liner.
The metal outer barrel provides the rugged structure needed for a large-capacity tumbler, while the thick rubber liner creates a quieter environment for the rocks and helps protect both the stones and the metal barrel during extended tumbling cycles.
The removable liner can also be replaced independently, helping extend the useful life of the machine.
Barrel Dimensions
Outer barrel:
- Approximately 8.5" high
- Approximately 7" diameter
Usable interior:
- Approximately 8" high
- Approximately 6.5" diameter
The barrel has an effective interior volume of approximately 300 cubic inches, or roughly 1.3 gallons of liquid volume.
Thick Rubber Liner for Quieter Tumbling
Large rotary tumblers can be noisy, particularly when hard rocks are continuously falling against one another.
The Model B addresses this with a approximately 1/4"-thick rubber barrel liner. The rubber absorbs much of the impact and sound produced during tumbling while also providing a durable surface for the rocks to tumble against.
The liner is removable and replaceable, so you don't have to replace the entire barrel when the liner eventually wears out.
Secure, Watertight Barrel
The Model B barrel is designed for wet tumbling, which is the standard method used to grind and polish rocks.
A metal lid sits over the rubber liner and is secured using six washers and wing nuts. A rubber gasket creates the seal between the liner and lid, helping prevent water and slurry from leaking from the barrel during operation.
The secure barrel design allows you to use water along with tumbling abrasives and media throughout the rock polishing process.
1550 RPM Thermally Protected Motor
The standard Model B rock-tumbling machine uses a 1550 RPM thermally protected motor.
The motor is designed specifically for the low-speed operation required for rotary rock tumbling. Thermal protection helps protect the motor by automatically shutting it down if it becomes excessively hot.
This is particularly useful during the long operating cycles required for rock tumbling.
The Model B motor is also designed to be serviceable, and replacement motors and other components are available if needed.
Important: The 1550 RPM motor is the rock-tumbling configuration. Thumler's also offers a high-speed 3000 RPM Model B configuration intended for other applications. For rock tumbling and polishing, choose the 1550 RPM model.
Designed for Long Tumbling Cycles
Rock tumbling is a process that takes time. Individual stages can run for several days, and a complete four-stage process can take several weeks.
The Model B is designed for this type of extended operation.
Its heavy-duty metal construction, thermally protected motor, durable rubber liner, and serviceable components make it particularly well suited to people who expect to use their tumbler regularly.
Rather than treating the Model B as a small hobby appliance, think of it as a durable piece of lapidary equipment designed to provide years of service with proper maintenance.
Excellent for Larger Rocks and Larger Batches
The Model B's large barrel provides more room for tumbling than compact machines.
It is especially useful when you have accumulated a significant amount of rough material or want to process larger batches at once.
As with any rotary tumbler, however, rock size and barrel loading are important. The barrel should contain a properly balanced combination of rocks, abrasive, water, and tumbling media. Very large rocks should not be tumbled together without considering the barrel size, material hardness, and potential for impact damage.
Built to Be Maintained
One of the advantages of the Model B's traditional mechanical design is that many of its components can be serviced or replaced rather than requiring replacement of the entire machine.
Replacement components are available for many of the Model B's wear items and mechanical components, including:
- Rubber barrel liner
- Barrel gasket
- Metal barrel lid
- Wing nuts
- Washers
- Motor
- Motor pulley
- Drive shaft
- Idler components
- Belts
- Barrel guides
This serviceable design is one of the reasons the Model B has remained a popular choice for serious rock tumblers.
Easy Maintenance
Like any mechanical tumbler, the Model B benefits from routine maintenance.
The motor should be lubricated according to the manufacturer's instructions, and the bearings and other moving components should be inspected periodically.
Keeping the barrel, liner, lid, gasket, shafts, and drive components clean and in good condition will help ensure smooth operation and extend the life of the machine.
Always follow the manufacturer's maintenance and lubrication instructions.
Ideal for the Four-Stage Rock Tumbling Process
The Model B can be used for the complete four-stage rock tumbling process:
Stage 1 – Coarse Grind
Removes rough surfaces, fractures, and irregularities and begins shaping the stones.
Stage 2 – Medium Grind
Continues smoothing the stones and removes scratches left by the coarse abrasive.
Stage 3 – Pre-Polish
Uses a much finer abrasive to prepare the stones for the final polish.
Stage 4 – Polish
Uses a fine polishing compound to produce the smooth, glossy finish that makes polished stones shine.
For the best results, keep abrasive materials separated between stages to minimize cross-contamination. Many experienced tumblers also dedicate a barrel or liner specifically to the polishing stage.
Specifications
- Model: Thumler's Model B
- Type: Rotary Rock Tumbler
- Construction: Heavy-duty metal frame and steel barrel
- Barrel Capacity: 15 lbs.
- Typical Rock Processing Capacity: Approximately 10 lbs.
- Number of Barrels: 1
- Motor: 1550 RPM
- Motor Protection: Thermal overload protection
- Barrel: Steel hexagonal barrel
- Barrel Liner: Removable rubber liner
- Liner Thickness: Approximately 1/4"
- Barrel Lid: Metal
- Lid Seal: Rubber gasket
- Lid Fasteners: Six wing nuts and washers
- Outer Barrel Height: Approximately 8.5"
- Outer Barrel Diameter: Approximately 7"
- Usable Interior Height: Approximately 8"
- Usable Interior Diameter: Approximately 6.5"
- Interior Volume: Approximately 300 cubic inches / 1.3 gallons
- Base Height: Approximately 8.125"
- Base Diameter: Approximately 9.125"
- Finish: Powder-coated metal
- Country of Manufacture: USA
- Warranty: One-year limited warranty
What's Included
Your Thumler's Model B includes:
- Thumler's Model B heavy-duty tumbler base
- 1550 RPM thermally protected motor
- Large 15 lb. metal tumbling barrel
- Removable rubber barrel liner
- Metal barrel lid
- Rubber lid gasket
- Barrel hardware
- Operating instructions
Tumbling Supplies You'll Need
The Model B is a rock tumbler—not a complete tumbling kit—so you'll need the appropriate rough stones, tumbling abrasives, water, and, when appropriate, tumbling media to begin polishing rocks.
For the typical four-stage process, you'll need:
- Coarse silicon carbide grit
- Medium silicon carbide grit
- Fine silicon carbide grit or pre-polish
- Rock polishing compound
- Ceramic or other appropriate tumbling media when needed
- Suitable rough stones
The Gemstone Lab offers a variety of tumbling grit, polish, ceramic media, plastic pellets, and rough rock to help you build a complete tumbling setup.
Thumler's Model B vs. Smaller Tumblers
If you're deciding between the Model B and a smaller tumbler, the biggest difference is capacity and construction.
A compact tumbler such as the Lortone 3A is excellent for smaller batches and beginners who don't need a large capacity. The Model B is a different class of machine, with a large metal barrel, heavy-duty construction, and substantially greater capacity.
Choose the Model B if you:
- Want to process larger batches
- Prefer a heavy-duty metal machine
- Tumble frequently
- Collect and process a lot of rough
- Want a machine designed to be maintained and repaired
- Don't want to outgrow a small tumbler
A Tumbler Built for Serious Rock Tumbling
The Thumler's Model B is a proven, heavy-duty rotary tumbler for rockhounds who want more capacity and a machine built to stand up to years of regular use.
Its combination of a 15-pound barrel, approximately 1/4"-thick rubber liner, steel construction, thermally protected 1550 RPM motor, watertight barrel, and replaceable components makes it a dependable choice for serious hobbyists and frequent rock tumblers.
If you want a large-capacity rotary tumbler that you can maintain, service, and continue using for years, the Model B is a machine worth considering
