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GUIDE: What is Rock Tumbler & How Do Rock Tumblers Work?

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Tumblers are mysterious beasts. It takes experience to get to know how any specific tumbler works, and almost never get it on the first try. I want to make sure to any beginner starts off with all the basics on how they work, how to choose a tumbler and what to expect, and what to do with the results, so that the learning curve starts off already high.

Tumblers work through facilitating collision, abrasion, and friction between rocks, water, and grit. Over time, with the right recipe and steps, these processes turn raw rocks into smooth, rounded, polished stones. Beginners should be aware of electricity costs, noise concerns, and all the possibilities that exist for beautifully tumbled stones.

Read more for a complete beginner’s guide into everything about tumblers.

If you are interested in checking out the best rock tumblers you can find them by clicking here (Amazon link).

What is a Rock Tumbler?

What is a Rock Tumbler and How do Rock Tumblers Work?
What is a Rock Tumbler and How do Rock Tumblers Work?

A rock tumbler is a mechanical device used to soften edges, round out, and shine rocks and minerals. It approximates the process which sea pebbles go through to get round and smooth, only in a shorter period. 

There are two main types of rock tumblers, but both rock tumbler types consist of two main functional parts: the motor and the barrel. The barrel is a container that holds the rocks and minerals to be tumbled. The motor provides continuous movement to the barrel.

Tumbled stones are used all over the world for many different purposes. It is a great way to bring out the inner colors of a stone, because all the hard edges, cracks, and jutting areas of a raw rock or mineral may not reflect the light in an optimal way.

Raw stones also are relatively uncomfortable to have in constant body contact, making them not ideal for jewelry. Tumbled stones are used for jewelry, souvenirs, art displays, and rock collections as a simple way to show the essence of a mineral.

Tumbling stones require a constant electricity source, a quiet space, rocks and minerals, and quite a bit of time to understand the inner workings of the process and the interactions between ingredients.

What to know about Rock Tumblers?

If you are debating buying a rock tumbler or trying to figure out how, why, when, or where to use one, here is a brief list of must-know facts about rock tumblers and the process they use:

  1. Rock tumbling is part science, part art.
  2. Tumbling takes a lot of patience to do right.
  3. It is a relatively inexpensive hobby.
  4. Rock tumblers can be loud, so the home you find for it matters.
  5. Though just a motor, it takes a considerable amount of electricity because It runs a lot of hours. (Consider solar panels for the environment!)
  6. Rock tumbling can be incredibly rewarding but is more rewarding if you find the rocks yourself.

Rock Tumbler Types

Rock tumblers come in two very different flavors. Consider carefully which type you want to buy as it will affect every batch of stones you want to tumble. 

The rotary tumbler works on the simple principle of rotation. The barrel has the shape of a true barrel of wine and continuously rolls for days on end.

This scientifically works very similarly to how waves would crash and then recede on a beach – other rocks hit each other, contributing to the rounding phenomenon, and water and grit flow around the rocks repeatedly. 

The vibratory tumbler uses friction to do the job. Stones are set in a pile of sand-like grit in the barrel. The motor vibrates the barrel with a high frequency so that each grit particle rubs back and forth on a single area of the stone. Vibratory tumblers are also used for polishing metal objects like coins.

Rotary tumblers use a much more natural process and then can run slightly slower than vibratory tumblers. For example, the same batch of stones might take a week in a rotary tumbler, but only 3-4 days in a vibratory tumbler.

Keep this in mind if you have a lot of stones to tumble! On the other hand, rotary tumblers are generally less expensive and longer-lasting. 

The main difference in the final product of these two types of tumblers shows in the shape of the stone – rotary tumblers can knock a large amount of material off the rocks, making them very round. Contrarily, the main job of a vibratory tumbler is to smooth material – so the product will be of a similar shape.

Carefully consider the application, whether the tumbler is for you or someone else. There are many other things to consider in this decision, this summary just scratches the surface.

How Do Rock Tumblers Work?

To approximate the natural process of shaping stone, it is natural to ask – what does a rock tumbler do?

Rock tumblers work on the basic principles of repetitive impact and friction to shorten a thousand-year process into a few weeks, all thanks to the invention of very basic mechanical tools.

The main component of tumblers is the motor. A motor uses an alternating electric current to induce a changing magnetic field. Just as you can manipulate a magnet to spin on a table with its opposite magnet, the alternating current can spin gear or a belt.

In the case of a rotary tumbler, this rotation only occurs every few seconds and is transferred via a belt to a spinning pin, on top of which the barrel sits.

On the other hand, in vibratory tumblers, gears are used to change the spinning rate. A weight is then unevenly distributed on this spinning object to make the barrel of a vibratory tumbler rock back and forth quickly (or vibrate).

Inside the tumbler, water and fine grit are placed in a solution with the rocks and minerals. The water slowly and iteratively eats away at the rock, while the grit provides the friction of sandpaper to speed up the process.

As the rocks tumble into each other in a rotary tumbler, they collide, trapping grit in between them and causing the smallest of pieces to fall off.

Given enough time, small pieces will fall off on the most exposed parts of each stone, shaping the stone closer to a sphere.

Vibratory tumblers count on the friction of rock and grit to happen without rocks colliding. Because of the frequency of vibration, this is extremely effective because it ends up in 100-1000 more “back and forth movements” as would happen in the rotary tumbler.

TIP: To get the best possible results when tumbling rocks it is good to know what rocks are good for tumbling and what rocks can be tumbled together. Check out all of them in the articles below:


What Rocks Are Good For Tumbling? 15 Best Rocks & Minerals


What‌ ‌Rocks‌ ‌Can‌ ‌Be‌ ‌Tumbled‌ ‌Together:‌ ‌Complete‌ ‌List‌ ‌With‌ ‌Tips‌


How Much Power Does a Rock Tumbler Use?

A tumbler’s energy cost depends on how big the tumbler is and what type you are using. Because it depends so much, I want to do a calculation example to teach you how to calculate usage based on a tumbler’s wattage rating. 

Before we start out, I want to point out that motors only work for a specific voltage range. Electricity grids on different continents use different voltages, so if you travel or move abroad you can never expect a motor-powered device to work if the voltage is different (most notably Europe and the US use different power grids).

Using a US tumbler in Europe or vice versa will break the motor.

Now let us take an average rotary tumbler of 50 Watts, or 0.05 kW (equal to 5-10 LED light bulbs). If we take this tumbler and change loads often so that we are using it 24/7, which is typical for tumblers, we end up at 31 days times 24 hours/day, or 744 hours per month.

Using Power = Energy * Time (high school physics!), we see that this tumbler uses 37.2 kWh in a month. In Switzerland, the electricity rate is $0.22 per kWh. Therefore, this tumbler will cost me around $8 per month in energy, and the atmosphere around 34 lb of CO2 per month.

Unit / CostsRotary TumblerVibratory Tumbler
Watts5070
Monthly Energy37.2 kWh52.1 kWh
Monthly Energy Cost$8.00$11.50
Monthly CO2 Released34 lb47.9 lb
Average Cost of Tumbler Operation

How Loud Are Rock Tumblers?

The rocks colliding and vibrating around cause a noise that is generally uncomfortable to have in one’s bedroom. However, if you are like me and grew up with siblings, then you can turn anything into white noise and you will not have much of an issue with a tumbler. 

In seriousness, the main issue people can have with a tumbler is its noise, so you are right to ask.

So, are rock tumblers noisy?

Vibratory and rotary tumblers exhibit a comparable noise level. It is akin in level to a washing machine. While a rotary tumbler can sound more like a beach with waves approaching at three times the speed, a vibratory tumbler is much more mechanical – something like a drill or an electric toothbrush.

At three feet away, the dB level can be anywhere from 61-69. This range is also attributed to the noise level of a normal conversation on a busy street. Therefore it’s a good idea to put the tumbler in an area where it’s normal to have constant noise, such as a kitchen.

How Fast Does a Rock Tumbler Turn?

Rotary tumblers (vibratory tumblers do not turn) make a full rotation anywhere from 10 to 38 times per minute. Certain tumblers have a customizable rotation rate, these are usually on the higher end in quality and price.

The average rate for an intro tumbler25 RPM
Optimal rotation for Polishing10 RPM
Initial step rotation rate30-38 RPM
How Fast Should a Rock Tumbler Spin?

It is a good idea to match the rotation rate with the grit coarseness – higher rates with larger grit – to keep the grit always in solution with the water. Larger grits (for earlier tumbling stages) are heavier and tend to sink down to the bottom of the barrel, especially when it is rotating slower.

This is always good to keep in mind when you are thinking of the ideal method of tumbling your stones.

TIP: Talking about speed, it is always good to know how it takes to tumble different rocks. Find out the accurate tumbling times for the most common rocks in the article below:


How Long Does It Take To Tumble Rocks? Values For Various Rocks


How Much Do Rock Tumblers Cost?

You can break the cost of a tumbler down into the tumbler itself, operation, and grit.

The grit cost is very little compared to the rest – around $25 for a set of grit which you should get at least 8 months out of. Some rockhounds recommend running a tumbler with more grit, saying that this takes less time.

Electricity cost is the next cost, and this one will largely depend on the cost of electricity where you live (remember, CO2 produced by the electricity you use is independent of cost).

Unit / TypeCosts
Electricity cost (monthly)$4-$8
Grit cost (monthly)$2-$4
Kids Tumbler$40
Hobby Rotary Tumbler$130
Hobby Vibratory Tumbler$110
Large Professional Tumbler$300
Costs of Tumbling

What is a Rock Tumbler Used For?

First and foremost, rock tumblers are used to tumble stones! But what is the purpose of this rock tumbler? Professionals use it to create jewelry quality specimens out of raw stones, hobbyists use it for the same, or to brighten up their collection, and kids use it to make normal rocks look shiny and beautiful.

Tumbled rocks are used for many things other than just collections, souvenir stones, and jewelry though. They make fantastic displays out of just about anything.

Many times, you’ll see them filling up vases, in jars around the house, as ground cover in planters, used in artwork for a wall, or crafts for kids.

Otherwise, what are the uses of a rock tumbler? What can you do with a rock tumbler?

Rotary tumblers are not very versatile in that they are meant for rounding out and smoothing out stones. On the other hand, vibratory tumblers are used to get the rust off coins, bullet shells, and other metal pieces by other hobbyists.

Why Use a Rock Tumbler?

There are other options to smooth or round stones, such as a Dremel Drill. So what does a tumbler do better than these options? Mainly, it takes manual labor out of the equation.

Typical rock tumblers can hold 3 pounds of stone, but there are barrels for professional rock tumblers that go up too much more than that. To manually take a tool to smooth out all the corners of 3 pounds of raw stone would take many hours. With a tumbler, you can fill it up, turn it on, and walk away.

Of course, there are the extra costs of a rock tumbler over a Dremel, but most people acknowledge the work saved as more important.

However, if the shape of the final product is very important to you, using a tumbler will not give you as much control as you need – in these cases, a tumbler is not the best tool for the job.

If you are in the market for a tumbler or just want to check out some of the best quality and highest value choices, here are my top picks (Amazon links).

  1. Lortone 3A Single Barrel Tumbler
  2. Tumble-Bee Rotary Rock Tumbler
  3. NATIONAL GEOGRAPHIC Hobby Rock Tumbler Kit

TIP: Using a rock tumbler can cause that it starts to leak sometimes. It’s common for all of us and you can fix most of the leaks easily. Find out more about the most common problems and how to fix them:


6 Reasons Why Your Rock Tumbler Leaks and How to Fix it


How to Use a Rock Tumbler

Rock tumblers are like ovens. They are fantastic for the job they do, but some jobs are better suited for a stove. However, if you are making a cake, the first step is to make sure you have the right mix of ingredients before you put the cake in the oven, otherwise, it will not be what you imagine.

In a similar way, the recipe is very important to use a tumbler. (They can also sometimes get warm, and that is OK.)

Before we talk about the recipe, it’s important to recognize that taking care of mechanical equipment regularly is key to their long life. Between loads, make sure to do a few things:

  1. Dispose of the grit and water in a safe location. The grit is not environmentally harmful but will clog a drain easier than a head of hair.
  2. Wash the barrel gently but thoroughly, making sure all the old grit is out.
  3. Put in the new recipe (more in this later) with the rocks you have chosen to tumble.
  4. Replace the barrel, making sure all moving pieces are tight but not squeezed. 
  5. Start up the tumbler, placed it in a flat and sound insulated area.

What to Put in a Rock Tumbler?

What to Put in a Rock Tumbler?
What to Put in a Rock Tumbler?

There are many theories as to what goes inside a rock tumbler, some more simple, some including up to 5 ingredients, changing depending on the step.

The theory of recipe changing throughout the process can be related to sandpaper – you switch a few times, increasing density, to get the softest result.

There are some overarching rules for tumbling that are generally not argued.

  1. Put rocks of similar hardness together. This makes their collisions more predictable and less damaging (soft rocks getting continuously pummeled by hard rocks is a recipe for dust)
  2. Put rocks of similar size together, for the same reason.
  3. Each load should go through 3-5 steps.
  4. The barrel should be anywhere from ½ to ¾ full, most recommend two thirds.

Here is the most common process for what to use in a rock tumbler (rotary), consisting of 4 steps.

Step 1: Use 60-80 grit material and fill the barrel with rocks to three-quarters full. Fill with water until just below the level of the rocks. Tumble for a week, or two if you want the shapes to be closer to spheres. This step mainly uses rocks hitting each other and grit to shape the rocks.

Step 2: Use 240-400 grit material with the same rocks (which will look less after the first step). Use the same idea with the water. This step takes care of most edges and corners. Tumble for 4-7 days.

Step 3: Use 600-800 grit material with the same rocks, with the same water idea. This finishes the rounding process and is the main smoothing process. Tumble for 3-5 days.

Step 4: Use 1200 grit material with the same rocks and slightly more water. Some glass dishwashing liquid is optional. Tumble for up to a week. This step polishes the stones and can be repeated if necessary.

TIP: Proper rock tumbler loading is really important. Especially when it comes to grit and rocks. Check out this complete guide about rock tumbler loading:


Rock Tumbler Loading: How Much Grit & Rocks Do You Put In?


Are Rock Tumblers Safe?

Rock tumblers are not at all dangerous in the hands of a responsible adult. While they are mechanical equipment, the motors are always encased and there is nothing that can be harmful in a normal application.

In the case of a curious or clumsy child, there are some considerations whenever moving parts are concerned. Fingers can get pinched input in the wrong spot.

Make sure any young one knows not to touch moving mechanical pieces, which may be partially exposed on any tumbler not meant for kids.

Kids’ tumblers are usually built to be handled by children but will always require supervision about how it works.

In general, never disassemble anything when it’s in operation. Always turn it off and unplug it to dive into the inner pieces and keep the cover on during normal operation.

FAQ about Rock Tumblers

I hope you found the answers to all the questions about rock tumblers in this article. But if you still have some other questions, below are some common and interesting questions about rock tumblers.

Can You Use a Cement Mixer as a Rock Tumbler?

The only application for a cement mixer as a tumbler would be for large stones. It is ok to do so, but only to accomplish rock rounding through collision. 

Polishing in a cement mixer will never work because they do not have the cushion required to make the fine grit work its magic. The fine grit will also wear down any steel after a few days, destroying the equipment.

Can You Turn a Rock Tumbler Off at Night?

You can turn a tumbler off at night, but your batch will take 2 times as long because it works based on the number of hours it is running. Therefore, it is always recommended to find a place either outside or in a louder place to let your tumbler run during the night.

What is the Biggest Rock Tumbler?

Thumler sells a vibratory tumbler that has a barrel holding 10 pounds of rocks. And a rotary tumbler that can hold 15 pounds of rocks. These are generally considered the largest you can go without sacrificing quality.

What is the Quietest Rock Tumbler?

There are two things you want to look for when looking for a quiet rock tumbler: it must be small and it must be a rotary tumbler with a rubber barrel. Not only do rubber barrels soften the sound level, but they also make it less piercing and uncomfortable. Quieter tumblers will resemble the sound of a dishwasher.

Does Rock Tumbling Really Work? Conclusion

Smooth, shiny rocks can be achieved with either kind of rock tumbler. Make sure you buy the right tumbler for your needs, follow the correct recipes and safety precautions, and take very good care of your equipment, and it will last you years of constant production. 

The main downsides of tumbling are the time it takes, the sound which it can produce, and the electricity it needs.

On the other hand, the upside of beautiful, round, shiny stones, with which to undertake any crafting project or make any household display, are agreed to outweigh the downsides.

If you want to check out some of the best quality and highest value rock tumblers, here are my top picks (Amazon links).

  1. Lortone 3A Single Barrel Tumbler
  2. Tumble-Bee Rotary Rock Tumbler
  3. NATIONAL GEOGRAPHIC Hobby Rock Tumbler Kit

You can also check the full article about the best rock tumblers for beginners and hobbyists, you find more details about these tumblers there.

TIP: Tumbling rocks is a very satisfying activity. And even more, if you tumble the rocks you found yourself. Check out the rockhounding locations in different states of the United States and find your own rocks for tumbling:


The Best Rockhounding Locations in the USA