How to Polish Rocks with a Bench Grinder (Ultimate Guide!) - Pretty Pebble (2023)

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.

How to Polish Rocks with a Bench Grinder (Ultimate Guide!) - Pretty Pebble (1)

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:

(Video) Rock Polishing with an Angle Grinder

  • 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?

How to Polish Rocks with a Bench Grinder (Ultimate Guide!) - Pretty Pebble (2)

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.

(Video) Petoskey Stone polishing on a buffing wheel

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.

How to Polish Rocks with a Bench Grinder (Ultimate Guide!) - Pretty Pebble (3)

Some Essential Reminders and Tips for You

Please take note of the following:

(Video) How to Polish Rocks with a Dremel

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.

(Video) Polishing Rocks By Hand

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.

How to Polish Rocks with a Bench Grinder (Ultimate Guide!) - Pretty Pebble (4)

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.

(Video) How to Easily Polish Rocks By Hand

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.



Can you polish rocks on a bench grinder? ›

✅ Multipurpose Grinding Machine – This professional-grade mini grinder is ideal for polishing, grinding, and buffing metals, gems, rocks, and other materials. And with a cast aluminum base it provides enhanced stability, durability, and resilience.

How do you polish rocks and pebbles? ›

Polish stones by hand with 60 grit sandpaper. Dip the stone in water, then use 160 grit and 360 grit sandpaper to smooth it. Alternatively, polish them in a tumbler. Buff stones with a powdered polish, then wipe them down with a strip of leather.

What is the best grit for polishing rocks? ›

Even though there are different kinds of rock tumbler grit, silicon carbide is the preferred grit for rock tumbling. This is because silicon carbide has three desirable characteristics: Silicon carbide is hard. Silicon carbide can be crushed into sharp, angular particles.

What is the best tool for polishing rocks? ›

A rock can be polished with a handheld Dremel drill. A Dremel is powered by its high speed rather than its torque. Depending on the attachment, a hand rotary tool can be used to do a wide variety of tasks, including drilling, cleaning, grinding, carving, sharpening, sanding, and engraving.

Can you turn a bench grinder into a polisher? ›

You can turn your angle grinder into a polisher by using a taper adaptor. Most grinders have a 14mm thread. Please check the diameter of the thread. M14 for a 4 1/2″ angle grinder is the most popular.

How do you polish rocks for beginners? ›

To do so, put the rocks and any filler into the barrel and fill it with water until the level reaches just below the top of the stones. Then add a few drops of natural dish soap (this is the one I use). Close the barrel and let it run for 1-2 hours. Then rinse it all out thoroughly.

What is the fastest way to polish rocks? ›

Use denim fabric to rub the rocks until they shine.

A piece of soft cloth like denim is the best option to polish rocks. If you don't have denim, you can use 600-grit sandpaper to polish your rocks.

How long to leave rocks in polish? ›

This usually takes between three and seven days depending upon the type of rock and their starting condition. The rocks are then processed two or three days in fine grit (also called pre-polish), and two or three days with polish. So, vibratory tumbling generally takes between one and two weeks.

How do you make pebbles shiny? ›

Jojoba oil is one good choice, as it will not become sticky or rancid as some kitchen oils will. Thoroughly soak the rocks in oil and allow 5-10 minutes for it to soak in. Then gently remove excess oil with an absorbent cloth.

What grit number for polishing? ›

400/ 800 grit – FINE HONING – These grits are considered the starting steps in the polishing process. Used to remove light scratches, acid etching and general ware damage. These grits will produce a dull to satin shine. 1500/3000 – POLISHING – The final stages in the polishing process.

What size grit for rough polishing? ›

An abrasive grit size of 180-240 [P180-P280] is coarse enough to use on specimen surfaces sectioned by an abrasive wheel. Hack-sawed, bandsawed, or other rough surfaces usually require abrasive grit sizes in the range of 120-180 grit [P120-P180}.

What is the best final polish for stones? ›

1. Cerium Oxide – The Go-to Polishing Compound. Cerium oxide is readily available, easy to use, and handles the majority of stones very well.

How do you make rocks shiny after polishing? ›

Then add some Borax (link to Amazon) or Ivory bar soap instead of grit or polish. Use about 1 tablespoon if you have a 3-pound tumbling barrel. You only need to run the tumbler for a couple of hours to achieve the desired effect. The Borax will thoroughly clean and polish the rocks to a high mirror shine!

How do you clean rocks so they shine? ›

The safest liquid to try first is water with a little dish soap. Soak your finds in soapy water for a day to loosen any packed-in dirt, and wipe or brush them clean. An abrasive toothpaste can also dislodge grime from smaller surfaces. Many collectors choose to remove calcite from rock and mineral specimens.

What are 4 rules for a bench grinder? ›

Safety Rules

Dust mask advised. Don't wear loose clothing or gloves, keep long hair tied back. Grinders are not recommended for material other than metal. Never grind aluminum or magnesium.

What not to do when using a bench grinder? ›

  1. Do not use faulty equipment. ...
  2. Do not hold workpiece with gloves, cloth, apron or pliers.
  3. Do not grind non-ferrous metals.
  4. Do not grind on the side of the wheel.
  5. Do not hold small objects by hand.
  6. Never leave the machine running unattended.
  7. Do not bend down near the machine while it is running.

What is the final step in rock polishing? ›


This the final step of rock tumbling. Fill a clean barrel with the smooth tumbled stones and add two levels of your favorite rock polish and then water to just below the rock level. Start the tumbling machine and run it for a week. After one week stop the machines and remove your rocks from the barrel.

What medium do you use to polish rocks? ›

The Bottom Line. Use ceramic tumbling media if the primary goal is to create better tumbling and grinding action to create well-rounded rocks. Plastic pellets are a better tumbling media to protect delicate rocks in later tumbling steps. If using a vibratory tumbler then you should only use ceramic tumbling media.

Does vinegar polish rocks? ›

Cleaning Rocks with Vinegar

Leaving rocks to soak in acidic solutions like vinegar or citric acid will remove calcite and other calcium minerals from the rock. After the rock has soaked for 2-3 days use a brush to scrub away any unsightly stains and loosened calcite.

What mineral makes rocks sparkle? ›

Mica is the mineral responsible for putting a sparkle on many rocks. This mineral is very flexible, and large sheets of it were used as window glass in the past.

What oil is good for polishing rocks? ›

Jojoba oil is an excellent option since it does not grow sticky or rancid like other cooking oils. Soak the rocks in oil well and wait 5-10 minutes for it to absorb. Then, using an absorbent towel, carefully wipe away any excess oil. After hand-sanding, mineral oil makes an excellent polishing oil.

What kind of materials should not be worked on the bench grinder? ›

Grinder should not be used when working with non-ferrous materials such as brass, aluminum, copper, plastics or wood. The material can become imbedded in the grinder wheel creating pressure that could shatter the wheel.

Can you use a grinder on stone? ›

An angle grinder is a power tool that can be used for cutting through different types of materials, including metal and other solid materials such as bricks, aluminium, stone and concrete.

What would you not do when using a bench grinder? ›

Safety Rules

Don't wear loose clothing or gloves, keep long hair tied back. Grinders are not recommended for material other than metal. Never grind aluminum or magnesium. Chance of fire.

Should you use gloves when using a grinder? ›

Gloves and Grinders – UNSAFE OSHA

Never wear gloves with grinders. Or operate grinders with guards removed. By “grinders,” we mean abrasive belt grinders, bench grinders, pedestal grinders, surface grinders, and also abrasive cutoff machines. No Gloves!

Where should you stand when turning on a bench grinder? ›

Stand to one side when starting a grinding machine. Damaged wheels will sometimes fly apart, and this is most likely to happen when the machine is being started. Stand to the side so that you will not be in-line with the debris. Do not grind on side of wheel unless wheel is specifically designed for such use.

What are the two most commonly used materials used for grinding stones on bench grinders? ›

Aluminum oxide provides exceptional value and cost-effectiveness while still offering the excellent quality and consistent performance necessary in a grinding wheel. Silicon carbide: Silicon carbide is an extremely hard grain that is very sharp and fast cutting but friable, not as tough as other grains.

Does a bench grinder need to be bolted down? ›

Machinery, such as grinders or buffers, must be secured to a work bench or pedestal and the bench or pedestal, in turn, must be secured to the floor to prevent walking or moving.

What are the stones on a bench grinder for? ›

Essentially, bench grinders are just tools for spinning grindstones, and these grindstones are for gently shaping metal. They're commonly used for getting blunt tools back to full sharpness, but they're not a one-stop-shop for instantly putting an edge on a tool.

Can you use a bench grinder for lapidary? ›

To remove small pieces of (thin) gemstone you can better use a bench grinder.

Can you use water on a bench grinder? ›

To cool it down at a regular interval you need to dip it in water. The best way to avoid edge deformation is to hold the tool to the grinder only for a few seconds and then dip it in water. Grinding small objects can be dangerous if your hand gets too close to the grinding wheel.

What are 2 uses of bench grinder? ›

Depending on the bond and grade of the grinding wheel, it may be used for sharpening cutting tools such as tool bits, drill bits, chisels, and gouges. Alternatively, it may be used to roughly shape metal prior to welding or fitting.


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