It’s not practical to polish small pieces of metal or rocks by hand. You can use a machine to simplify your work. Unfortunately, machines are expensive, and not everyone can afford to buy. If you desire a machine, but can’t afford one, you can opt to make a DIY rock tumbler. The machine can make any small rocks shiny and round. 

In this post, we’ll look at some things you need to make a rock tumbler, plus detailed instructions on how to make a DIY rock tumbler. 

What is a Rock Tumbler?

A rock tumbler is an instrument that helps to smoothen the rock surfaces. Commercial rock tumblers have a motor that helps to rotate the tumbler. However, the homemade tumbler does not use motors but incorporate a technology that naturally smoothens the rocks. 

Popular tumblers have a barrel loaded with abrasive grit, water, and rocks. The grit consists of granular material which is the same as grains you find on sandpaper. Also, the grit is classified as fine, medium, and coarse. 

The tub is put on a motorized machine that rotates it to tumble the rocks. The tumbling actions force the rocks to grind against each other and mix with the abrasive grit. What’s more, tumbling removes the rocks’ sharp edges and smoothens the surfaces. These machines are rotary tumblers. The finished product is brightly polished stones.  

What Type of Rocks Need to Be Tumbled?

While you can use any rocks in the tumbling process, it’s best to understand that some stones perform better than others do. When using a tumbling machine, you can opt for jasper, chalcedony, and agate as they are sturdy and durable. Moreover, they give you a bright polish as they have microcrystalline quartz.

Some of the qualities you need to look for in good tumbling rocks include:

  • Hard -  Avoid tumbling rocks with a Mohs scale of more than seven. Ideally, a low Mohs makes the rock softer. A range of seven is recommended for tumbling. Rocks like sapphire and ruby are hard, while stones like marble and soapstone are thin. Soft rocks are difficult to smoothen in a tumbler. Also, hard rocks with a Mohs scale of more than eight do not give you a good polish in the tumbler. You can get a hardness testing kit to find out the rocks hardness. 
  • Dense and without pore spaces and voids - Good tumbling rocks shouldn’t have pore spaces, as these spaces trap grit and could carry it to all steps of the tumbling process. If there’s contamination in the polishing step, you won’t achieve that beautiful finish on your rocks. Pick out any rocks with pore spaces or voids.
  • Free of Fractures - It’s essential to select rocks that are free of fractures, cavities, and voids. Ensure that the rocks have a non-granular texture as this will influence the final product. Fractures could also break up the rock in a tumbler. Moreover, the sharp edges on these pieces scratch every rock in the barrel, interfering with the product. Remove any rocks with visible fractures before beginning the tumbling process. 
  • Smooth Texture - the right tumbling rocks need to break down to form smooth and shiny rocks. Avoid picking rocks that are grainy or gritty. You can rub the rocks together to see if any particles dislodge. If you notice that the rocks produce granular debris, choose other rocks as these won’t polish. 

You can get these rocks in nature. Places with lakes and those with a past volcano activity have plenty of these rocks. Rocky beaches are also an excellent place to get rocks like agates. 

Avoid tumbling rocks with a Mohs scale of more than seven. Ideally, a low Mohs makes the rock softer. A range of seven is recommended for tumbling. Rocks like sapphire and ruby are hard, while stones like marble and soapstone are thin. 

What Can You Do With The Tumbled Stones?

You can use the tumbled stones as craft supplies, give them as a gift with etched messages, or use as decorative pieces. Tumbled rocks can help make:

  • Paperweights
  • Keychains
  • Plant filler
  • Jewelry
  • magnets

Items You’ll Need

  • A wide mouth plastic jar
  • Screws
  • Drill
  • Glue

Directions on How to Make a DIY Rock Tumbler

To get started, you need to get a plastic jar like that of peanut butter or mayonnaise. Use a metal or any material as a spacer, as this helps you extend the rod to both ends of the jar. You may opt to use rubber matting to extend the durability of the plastic.

Fill a few inches of the jar with equal parts of water and sand. The sand causes the abrasion, a function that smoothens the rocks. You can use coarse sand at the start and fine sand when you notice the rocks getting smoother. Water and sand form a slurry also called grit. 

You need to drill a hole at the center of the lid. Ensure that it’s small enough to fit a bolt tightly. Apply hot glue or super glue around the hole. Alternatively, you can opt to use O-rings or rubber washers if you can’t find glue.

Place a bolt through the hole and check to see if the bolt sticks out of the top. Tighten the second bolt to lock the position immediately. Take time to allow the glue to dry completely. Put in the rocks and screw on the lid. You need to tighten the drill around the bolt tightly to ensure it doesn’t move. Push the trigger and allow the rocks to tumble.  

The rock tumbling process starts with rough-edged rock, with the final product being smooth rocks with a polished surface. You should realize that the process may take a month or more to smoothen the stones. 

A DIY rock tumbler replicates the natural stone smoothing process. With the natural process, stones in streams and rivers tumble because of the flowing water. When you place rocks in the container, they topple on each other and eventually blend with the grit.

Remember to use coarse sand at the initial stage and fine sand at later stages. Silicon carbide can work as an alternative to sand and water if you plan on getting better results

How Long Does the Tumbling Process Take?

The process of rock tumbling varies depending on the rock type. Rocks like fluorite, marble, calcite, and obsidian are soft rocks. They shape quickly in a rock tumbler. Marble and Calcite have a Mohs hardness of 3 and will round nicely in three days max.

Obsidian and Fluorite have a Mohs hardness of 4-5.5 and take up to five days to round nicely. Rocks like Agate and Jasper have a Mohs hardness of seven. They require more time to polish and shape in the tumbler. However, the results are impressive at the end of the wait. 

Additional Rock Tumbling Tips

Cleanliness is vital in the tumbling process. Ensure that you clean the barrel, the rocks, the lid, and anything else you’ll include in the process. You don’t want to end up with a slurry of finely ground rock, which prevents you from getting any polish on the rocks. Also, you may have contaminated coarse grit that ruins the polish.

It’s critical to understand that the tumbling involves a regular schedule. The steps listed above take a week in the tumbler. You need to keep track of your rocks to avoid losing track of time. 

Always cushion the rocks while tumbling. Placing large rocks in a tumbler may not be the best idea as they could cuff against each other, leading to micro fractures. Rocks like obsidian and quartz experience visible fractures that look like white spots. You can prevent this by using plastic pellets or ceramic media as a cushion. You can be sure this will enhance the polish and reduce damage. 

Also, make sure that you have rocks of all sizes. Getting large rocks will create gaps, and this could cause fractures. Mix both large rocks with small ones to fill in the gaps. The barrel should have 2/3 full of rocks. An empty barrel could throw the rocks around, leading to bruises. Add ceramic media as a filler if you don’t have rocks to fill the barrel. 

You should note that more tumbling doesn’t always lead to better polishing. Leaving the rocks in the tumbler for a long time could lead to scratches. A week is enough to get the best polish.


multicolored pebbles on a ceramic bowl

Image source: Pexels

We hope you’ve learned how to make a DIY rock tumbler at the comfort of your home. You don’t need sophisticated equipment or skills; all you need are some simple tools. You can have the children also help with the project, something that will help them learn and have fun in the process.

Whether you’re looking to spend time with your loved ones or make some unique crafts and jewelry, you can consider using a DIY rock tumbler to practice this at home. 

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