bench grinder

How to Polish Rocks with a Bench Grinder (Ultimate Guide!)

Rock tumbling can be quite expensive when you consider how much you spend on rock tumbler grit. People are coming up with ways to reduce or eliminate the cost of rock tumbling. For example, some people use bench grinders to polish their rocks.

Can you polish rock with a bench grinder? If so, how do you polish your rocks?

It is easy to polish rocks with bench grinders. You need to modify the sand belt or grinder plate so that they can easily polish your rocks. Also, you need to consider your safety so that you do not get injured.

What are some safety tips when polishing rocks using a bench grinder? What is the best material to use as a sand belt? We’ll answer these questions and more in this article.

well polished stone

Polishing Rocks Using a Bench Grinder

If you have a bench grinder, you should consider polishing your rocks with it. It is very effective and has more uses than a regular rock tumbler. Let us consider the pros and cons of using a bench grinder.


Here are some advantages of polishing rocks with a bench grinder:

  • Cost-Effective: You do not have to always purchase tumbler grit whenever you want to tumble or polish your rocks if you know how to use a bench grinder.
  • Bench Grinders Can Shape Many Types of Rocks: With a bench grinder, you can shape a wide variety of rocks. All you need is the right sand belt or disk.
  • Polish Rocks Quickly: You can spend more than three weeks tumbling and polishing your rocks in a rock tumbler. With a bench grinder, you can finish the entire process in less than one week.
  • You Can Decide the Right Shape for Your Rocks: Traditional rock tumblers will make your rocks round and smooth, but with a bench grinder, you can give your rocks multiple shapes. You can grind your rocks to have a cube, sphere, star, or any shape that you want.
  • Best for Large Rocks: If you do not want to break your large rocks that cannot fit into your rock tumbler, you should use a bench grinder to polish it as it is easier and more effective.


Some disadvantages of using bench grinders:

  • Not Safe: If you do not properly handle your bench grinder, you may get seriously injured. This means that you need to be very careful when working your rocks in a bench grinder.
  • Does Not Polish Rocks Effectively: Bench grinders can effectively grind and shape rocks, but they might still have a rough feel especially if you do not use the right plate or sand belt. You will need other methods to smooth your rocks.
  • Not Recommended: Many rock enthusiasts do not recommend this method of tumbling rocks because of local laws and also the safety.
  • Bench Grinders Can Break Your Rocks: If you do not handle your rocks with care, they may become broken when using a bench grinder.
  • You Cannot Polish Multiple Rocks: In a rock tumbler, you can put as many rocks as you want (i.e. rocks that can enter the tumbler barrel). When polishing rocks with a bench grinder, however, you can only polish one rock at a time.

You have considered the pros and cons. Do you still want to polish your rocks with a bench grinder?

bench grinder

How to Polish Rocks with a Bench Grinder

Polishing rocks with a bench grinder is easy as long as you have the right materials and you follow the safety tips.

To polish your rocks with a bench grinder, you need the following:

  • Bench grinder
  • Rocks (larger ones)
  • Cup of water
  • Shallow Pan

Have you gathered everything that you need? Here are some easy ways to polish your rocks:

1. Modify the Sanding Belt

You should use a diamond or silicon carbide belt as these materials can easily grind your rocks. They are very high in the Mohs hardness scale, so they can grind and polish any type of rock that you have.

2. Grind the Rocks and Dip Them in Water

Whether you are using a sand belt or grinder disk, you should dip the rocks in water often to cool them. During operation, the rocks can become very hot and may become broken if you do not dip them in water to cool off regularly.

Keep a cup of water beside you always.

3. Mount Your Belt-Driven Grinder in a Shallow Pan of Water

If you do not like the method of dipping your rocks in water regularly during operation, you can keep them in a shallow pan of water and install the bench grinder just above them. The rocks will cool off on their own in water and you do not need to keep a cup of water beside you.

Note that dipping or placing rocks in water is not recommended for carbide grinders because water wears carbide quickly.

4. Do the Pre-Polishing and Polishing Phases in a Rock Tumbler

If you cannot achieve a smooth feel in your rocks after polishing them with your bench grinder, you should use your rock tumbler (with plastic pellets and other types of grit) to polish the rocks.

Even though you are trying to save cost, always remember that polishing rocks with a rock tumbler is the easiest, most common, and most recommended way to polish rocks.

5. Oil Your Rocks Afterwards

After polishing your rocks, you should oil them to make them shiny and have a wet look. You can use clear nail polish, transparent acrylic paint, and different types of oils to make your rocks shiny.

When you are done, you should display your rocks as you have worked so hard on them. Display the rocks so that your visitors can see your hard work.

anvil and tong

Some Essential Reminders and Tips for You

Please take note of the following:

1. Your Safety First

Make sure that you use gloves and goggles and handle the bench grinder with care so that you do not harm yourself. If anything goes wrong, you can get injured, so you need to think about safety first.

2. Electricity and Water Do Not Work Well Together

Remember that water and electricity do not mix well. Make sure that water does not reach the motor of your bench grinder or it can become damaged and spark.

3. Hold the Rock with a Tool

You should use a clamp to hold the rocks so that they do not shake or fall when polishing them with a bench grinder. You can use pliers, but pliers are not highly recommended.

Always remember the tips above.

Related Questions and Answers

1. What is the Most Recommended Way to Polish Rocks?

Using a rock tumbler is the most recommended way to polish your rocks. You should only use a bench grinder when you know how to operate it and you know what you are doing.

If you are a beginner, please use a rock tumbler.

2. What Type of Rock Tumbler Should You Use?

There are basically two types of rock tumblers. Rotatory tumblers work by rotating the rocks and grit in a barrel until the rocks have shape and become smooth.

Instead of rotating the rocks and grit, vibratory tumblers work by vibrating the rocks in a barrel.

Rotatory tumblers are very effective, but take a longer time to polish rocks than vibratory tumblers. You also use more grit in rotatory tumblers. Vibratory tumblers, however, are more expensive.

You can use the type that works best for your situation.

3. Can You Use Broken Grinder Disks As Grit?

If the disk is made of diamonds, silicon oxide, or any other material that is harder than rocks in the Mohs hardness scale, you can use it as grit. Use a hammer or any heavy object to break the disk into smaller particles and use them as grit just like other types of grit.

Note that the different phases in rock tumbling have their preferred grit.

polished gemstone

4. Can You Polish Rocks with a Dremel?

A Dremel is a tool that can be used for drilling, grinding, or anything you need a rotating tool for. If you install the grinding head or disk in the Dremel, you can polish your rocks with it.

Just as in bench grinders, remember that you need to cool off the rocks regularly and also hold them with a clamp or plier.

5. What is the Mohs Hardness Scale?

Mohs hardness scale is a scale of the hardness of a material. For example, diamonds are the hardest materials while regular rocks are not as hard as diamonds. If you hit a diamond with a regular rock, the regular rock will scratch and not the diamond.

The principle behind Mohs hardness is that harder materials can scratch other materials and not the other way around. This is why you use grit to polish rocks in a rock tumbler. Most grit materials are harder than regular rocks.

Final Thoughts

You can use a bench grinder to polish rocks. Just make sure that you follow the safety tips listed in this article.

Also, remember that the easiest and most recommended way to polish rocks is by using a rock tumbler.


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