Super Simple Parts Tumbler (Metal Polisher)

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What can you do with this machine?

It is basically a polisher for all kinds of materials. I use it for steel, but you can also polish wood, plastic, or even minerals. If you put something in there with sharp edges, it will round them over until they are completeley smooth. It is very easy to build and can save a ton of time when you have to finish a lot of parts at the same time. The rounded edges are also very uniform.

Materials you need:

Tools you need:

Step 1: Plan Your Build.

How big should my barrel be?
Your barrel should be about 4x as long as the parts you want to tumble. Smaller tumblers can cause the parts to interlock. The barrel I chose is 15l big, but I should have gone with a bigger barrel to be able to also tuble bigger parts in the future. Here in Europe they are manufactured by Curtec and you can get them in watersports stores.

What type of barrels work?
Plastic drums are totally ok for this application. Especially HDPE is very resistant to abbrasion. Steel can rust and is more noisy, also more exensive. Work with what you can get. This is totally an application where you can upcycle some trash.

How big should the motor be?

My motor is rated for 1000W, but I don´t belive that at all. It runs at 150W with a 15l barrel. You can extrapolate from there.

Rotating or vibratory?

Vibratory is probably better since industrial machines use this, but I think rotating is easier to build and less likely to fall apart.


What kind of drive system is best?
I think a frition drive is very neat. It means that you can easily take off the barrel to fill it. You also don´t need any gears. The small shaft combined with the big diameter of the drum creates a gearing effect. A gearbox costs money, and alligning gears is difficult. Any other drive would also require to attach some way of force transmittor to the drum. That would just cost time and make it more complicated.

What is the best material for the friction drive?

Silicone tubing is very easy to apply and also durable enough. Rubber would be better, but It is harder to find.

Step 2: Add the Wheels!

Start by screwing on the wheels to the base plate, then you can use a spacer to get the barrel into position. The barrel should sit as low as possible for maximum stability. Some oil will do wonders on the bearings. Swiveling casters can also be used, but I think fixed is easier.

Step 3: Make Some Bearing Blocks.

I didn´t have any mountable bearings, so I made some plywood blocks that hold standard bearings. It is a good idea to make the blocks so that the holes are at the exact same height as the motor. That way the shafts are already alligned. Loose fitting bearing blocks make it easier to allign everything. If they are fixed, they need to be exact. Otherwiese they cause binding.

Step 4: Machine the Shaft.

The shaft needs a stop so it cannot slip through the bearings. You can use a solid steel shaft and machine some shoulders, or you can use a threaded rod and add nuts to stop it from moving around. I kind did a combination of both since I had a 12mm threaded steel rod and too small bearings.


A good source for suitable shafts are old printers. They are full of them.

Step 5: Mount Everything on the Base Plate.

I just screwed everything down to get a feel for the machine. It worked out alright. No changes where neccessary. I experimented with different materials to drive this machine and silicone was the best. At this point you can attach a cordless drill to see how it behaves.

Step 6: Mount the Extra Wheel. You Will Need It : )

No matter how well you allign your wheels and the shaft. Your barrel will tend to wander into a specific direction. That is not great but also not terrible. Just add some kind of wheel to stop it from going any further down.

Step 7: Attach the Motor.

My motor is not actually attahed to the base plate. It just sits there freely without any issues. At least for now. There are several ways to connet a motor shaft to a driven shaft. You can use flexible couplers like they use on 3D printers and CNCs. Chances are you don´t have any lying around, so you can use a hose and hoseclamps instead. This worked out very well.

You can also add gearing at this point to slow it down or speed it up, but in my experiece it is very difficult to allign gears without making them very precise and thick.

Step 8: Wire Up the Motor.

My motor runs off 24V DC, which is easy to get with a power supply. When buying power supplies, I always get one from Meanwell. The main reason is safety. I can be sure that these are tested. They supply the correct voltage and they have over current protection. They get mains power input, so they could potentially kill you if they are faulty, so don´t try to save money here.

The motor controller is not neccessary, but a nice touch. It slowly accelerates the machine which is nice, but not stricly needed. You can also use it to vary the speed. Whenever I buy such devices, I try to get one that already has a housing. Saves a ton of time.

Once everything is wired up, I like to check the current draw with a clamp style amp meter. These are very easy to use since you don´t have to disconnect any wires and there is no danger of destroying your equipment or blowing fuses.

Step 9: Run It!

I use granite gravel. There were plenty of choices in my hardware store, but I think granite is solid. It is very very rough and heavy. Apparently you are supposed to fill the drum half way.

How long does it need to run?

For Aluminium parts, 3 hours are normally enough to give me nice visibly round edges. For steel parts I run it for about 8 hours. It is noisy, but it also saves a lot of effort.

Have fun building one of these! It is very fast and nice to have.

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    4 Discussions

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    WeTeachThemSTEM

    8 days ago

    Thanks for sharing your process and the great tip for using sewing machine oil. :)

    1 reply
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    Alex in NZ

    8 days ago

    This looks great. Thank you for sharing your work, and especially for the very clear and comprehensive walk-through of the design decisions.

    1 reply
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    Max MakerAlex in NZ

    Reply 7 days ago

    You are welcome. I wasn’t sure if the design process would be appreciated.