Reasons Why Your Rock Tumbling Belts Keep Breaking (And Where to Get New Belts)

If you keep shredding up the rubber belts on your rock tumbling machine, then this article is for you. Listed below are common reasons why you might keep wrecking the belt.

Rock Tumbling Instructions

<I am going to include Amazon links to relevant products in this article. I make a small commission, but it doesn’t cost you anything, I promise.>

Rock polishing is a properly rewarding hobby provided that you have working equipment and a bit of knowledge behind you. For knowledge you can visit our rock tumbler instructions blog.

For troubleshooting why your belt keeps breaking, you are in the right place.

Why are my Rock Tumbling Belts Breaking?

There are a few reasons. Let’s troubleshoot.

1 – Age

Rubber has a shelf life regardless of how much you have used the belt. You could have a spare on a shelf for years, finally have the opportunity to use it, and find that it barely lasts a day. It’s just degradation of the rubber and there’s nothing you can do for this one.

I don’t want to link to a bunch of rubber companies so let me sumarise quickly instead. Heat, oxygen, and light all degrade rubber faster. The rubber belt on your rock tumbling machine will degrade faster if it is in use than if it is on the shelf.

Keep your spare belts in a dry, dark place. I also keep mine in a sealed baggy so that the air doesn’t get in.

2 – Oil on the Rubber

One of the first rock tumblers we got had an instruction manual in it which said to touch oil to the heads once a week or so, but to make sure the oil does not get on the belt as this can degrade the rubber. I am still not sure which part the heads is/are?

Easy solution for this one. Clean your rock tumbler machine with a mostly dry cloth while it is turned off at the mains. Soapy water gets rid of oil but you don’t want to get your motor wet, and you want the parts that move to be a little oiled.

3 – Overweight Barrels

This is probably the most common reason why the belt in your rock tumbler has broken. Your rock tumbler instructions will have the maximum weight which your tumbler can hold at one time in them.

Usually this goes up 0.5lbs at a time. Most tumblers hold between 1.5lbs and 3lbs. Our machines both take 2.5lbs. Some models, like the STEM rock tumbler, will not turn at all if the barrel is overweight.

Overfilling your rock tumbler presents multiple problems. Your belt might shred under the weight. You might not get the polish you want because the rocks have no room to move and therefore no friction. You might also overheat and break your motor, which is what powers the belt.

The best way to solve this problem is by weighing your barrel before you put it on your machine. Remember that water weight is very real and that you should weigh the barrel when it also contains water and grit.

4 – Lack of Space

I once shredded a belt to actual inch long pieces because I didn’t give it enough room. It was touching one of my other polishing machines. Every rotation it was touching the metal of the other machine. The rock tumbler belt could not cope with it. I don’t know how long it was running

that way but the belt was the worst I have seen.

5 – Environmental Extremes

Speaking of giving your rock tumbler space on the shelf, you should also be aware of the extremes in temperature that might affect them. We have two tumblers running at the moment, both on the same shelf, both inside a closed cabinet which we need to do to prevent the noise from reaching downstairs.

Now. The cabinet gets hot on normal days, so on extremely hot days, we often switch them off. You run the risk both of burning out the motor in your rock tumbler and/or wrecking your belt.

This goes the same for freezing temperatures. Anyone who has ever watched Gold Rush knows that you have to turn the equipment off to protect it from breaking when it gets too cold.

If you keep your tumblers in the house, then they are likely fine. If you keep them in the garage or shed, then consider switching them off when it’s too hot or too cold.

Where to Buy a Replacement Rubber Rock Tumbler Belt?

I don’t know for sure which size of belt your rock tumbler takes so these are just suggestions. You can always return them if they don’t work, which is the beauty of Amazon.

UK Replacement Rock Tumbler Belts

If it is a Nat Geo hobby tumbler or the equivalent then these Dan & Darci rubber belt replacements should fit it. Most hobby sized rock tumblers will take these belts.

US/CA Replacement Rock Tumbler Belts

You can view a full list of available replacement rock tumbler belts on Amazon.com here. This set of 4 rock tumbler rubber belts are cheap and cheerful. They go with National Geographic tumblers and Dr. Cool Rocks.

If you have a Leegol rock tumbler then they take specific belts. You can find replacements for the Leegol Electric belt here. The Leegol Electric 6lb rock polishing machine is another league but it is not compatible with our outlets here in the UK.

I still want one.

Further Troubleshooting a Broken Belt in Your Rock Tumbler

If you get through this article and none of the fixes work, then you should contact your rock tumbler’s manufacturer for additional information. They may even give you a replacement belt or two.