DIY Polishing Machine ~ Luthiery Laboratories

DIY Polishing Machine

This was my initial attempt at a polishing machine. Not pictured is the shroud I made for it to contain the spray.

This is for wet-polishing with sponges and automotive polishing compound. It is a very messy process - drops of "mud" fly everywhere. However, it does work. It takes great care to avoid going through the finish, which is a disaster. I have since moved to dry-buffing with cloth wheels.

The Harbor Freight polisher blew up a few days past the measly 90-day warranty. These Chinese tools often have almost no grease on the gears and bearings, and immediately start to tear themselves up inside. But I was expecting that, and had remedied it first thing, so I had to wait for some other part to fail. The trigger - easily replaceable, if you can get one, which you can't. That's today's lesson on cheap tools. I replaced it with a DeWalt that is still going like new.

Finishing

Black Polyurethane body. This is during the polishing process, you can see it is not even clean. The front came out like black glass. I smoothed the orange-peel with 1500 grit wet, then 2000 and 3000. Then I switched to the random orbital with a red sponge cutting pad and Turtle Wax rubbing compound that claims to remove 1200 scratches. Shouldn't be any 1200 scratches, since I started with 1500. That came out shiny, but with swirl marks in the light. Then I switched to another red cutting pad with Meguiar's Ultimate Compound, and finally a softer yellow pad with the same Meguiar's. At that point, it was pretty much a factory finish. I didn't work as hard on the back, it is nice, but will soon enough encounter a zipper or belt buckle, so the effort would be wasted.

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Welding

I was playing around with my new welder, and eventually, I did this. That is a 3/16" round attached to a 1/4" flat - a very common joint for a truss rod. It's not beautiful, but it is strong, you can see how I tried to pull it apart. Then I sawed the end off, and you can see it is solid - no slag inclusions, just two pinpricks at the 'corners' of the round. Welding is not as scary as I thought, but it is going to take a lot of practice. My welds seem to be a matter of luck, but my luck is improving.

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