Working with the “Other Mill”

AKA the “Bantam Tools Desktop PCB Milling Machine.” It just rolls off the tongue, right?

I wasn’t quite sure what to cut out with the Other Mill, but I did want to use at least two different materials. I settled on making a coin or coaster type thing out of acrylic with inlaid aluminum which is really just what I found lying around the shop.

Design

The main feature of the disk is the Chinese character for my last name, with a few changes to accommodate for the bit radius. Shown below is the final design with the dark areas representing the areas I want to be finished in aluminum.

The Chinese character (hanja) for my last name.

Milling-Acrylic

The file was pretty easy to output from Illustrator. Using the Bantam Tools software was also fairly easy when doing simple jobs like this. I can imagine this being tedious for larger jobs or multiple pieces, but for a one-off, it was just fine.

Lets get started!

Watching the router go was pretty satisfying. It is precise and reliable.

Milling acrylic can get messy

This job took about 30 to 40 minutes, but it came out perfect. The precision of the machine was on full display as it managed to cut through the plastic but leave the tape in tact. I couldn’t believe it.

The bit managed to glide right over the doubles-tick tape while cutting the acrylic all the way through!

I could have stopped here, but I still wanted to try it with the aluminum.

The fully milled acrylic piece

Milling Aluminum

Right out the gate, I ran into a problem: I failed to tape it down properly. This resulted in ruining my piece with an unsightly gouge.

Uh-oh…

Furthermore, the piece wasn’t big enough to cut another character without colliding with the ruined area. So I decided to shave 0.01 inches off the top to hide the scratch.

The piece came loose and resulted in this mess.

This job took much longer. It said it would take an hour and thirty minutes, but it ended up taking just an hour. Regardless, I didn’t really have enough time to do the outer ring and my last name, so I called it quits at this point.

Completed cut in aluminum

This time, the routing bit left a thin layer of aluminum connecting the piece to the rest of the material. It was almost as thin as aluminum foil. I peeled the piece out and tried to see if it would fit in the larger piece of acrylic.

The aluminum piece fits perfectly!

It fit perfectly! However, when i tried to take it out, I realized that it was stuck in there permanently. If I had known that it would fit so well, I probably would have made sure the aluminum piece was cleaner. I also realized that after I shaved that top layer off the aluminum, it was no longer flush with the acrylic, which was more what I was going for.

Finishing

In order to get the pieces flush, I decided to just use the power sanders in the shop. Upon reflection, I think a better option would have been to just put the whole piece back into the Other Mill and have it shave off the top layer of the acrylic. This worked too but required me to be more hands-on.

The palm sander frosts acrylic very evenly.

I tried reducing the acrylic thickness using the palm sander, but I realized ultimately that I would have to use the belt sender to take off that much material.

I mounted the piece to a block of wood so I could hold it against the belt sander to get the two materials flush.

In the end, I whittled it down to a flush finish, but the acrylic ended up uneven in some areas—less than ideal. I then ran it under the palm sander one more time to clear out any visible scratches.

The finished piece with inlaid aluminum. No glue was needed.

The Other Mill is pretty amazing when it comes to accuracy. The time it takes to cut is considerable, though. For cutting metals, it seems like the only choice. For acrylic, its etching capabilities are great, but for quick cuts, I think I’ll still use the laser.

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