YAMAHA CHOPPER PROJECT
DESIGN | MAIN | ASSEMBLY

2004/11/15:
So a month ago, the aluminum on the bike looked like this:

But that's when JP dropped by to teach us all about polishing metal. As an example, he grabbed one of the tappet covers.
Lesson 1: under that scratched, dented, discoloured surface, there's bright shiny metal. You just have to get to it. He tore in with some coarse emory cloth.
Lesson 2: now you have to take out all those scratches you made by using a slightly finer sandpaper. And now that you have new smaller scratches, take them out with finer sandpaper yet. And repeat, until the sandpaper is so fine you can hardly tell it from regular paper. So over the next few hours, he moved up the sandpaper ranks, up to 1500 grit with a little added oil. Finally, the metal was treated to metal polish and a cotton buffing wheel that JP was kind enough to donate to The Barn. Here's how the tappet cover ended up:

Tim quickly discovered there was a way to skip half the sanding effort. Start with a wire wheel bolted to a grinder:
This lets you go from ugly raw metal to this in a few easy minutes:

So it's obviously a much shorter trip to get here:


But that trip is still one that seemed best done by hand. Pieces had subtle curves and tight little sections that a machine just can't form to the way your hand can.
So after a little trial and error I figured out my system. The key is to remember that at any stage, if you see an imperfection that you didn't create with the current coarseness of sanding, that imperfection will be there until the end. If you can't make any scratch disappear in a minute or so with the paper you have in your hand, it's time to go back up a coarseness and take it out before you move on. Otherwise you'll just waste time and paper polishing away before realising you have something that looks like a giant scuff and deciding you have to go back to the grinder. So here's my routine:
- Start with the grinder, and make sure every little scratch is ground out.
- Go to 400 grit and spend a few minutes on every square inch. If you think you've got an area done, do it again for twice as long.
- 600 grit, do the same.
- 800 grit.
- 1000 grit. This one you should spend much more time, because the grit spacing is getting further apart. Also the paper wears out faster.
You'll notice a lot of sandpaper dust collecting on your hands.
- 1500 grit. If it doesn't look pretty much perfect after 1500, then go back. Whatever the worst blemish is, figure out what grit you need to remove it. Remember that at all stages you should be making progress without using pressure. Let the paper do the work.
- Last step is the Polishing Wheel. This part is just gravy. Smear on some polish and buff it back to a shine.

Last weekend had nothing planned, so I just sat myself down in the living room and went to town. I'm a little too lazy to do a perfect job, but it worked out well enough. A few hours with the right side case, and I had this:
So I grabbed the last couple pieces, and on Monday all the aluminum was shiny and reflective.

DESIGN | MAIN | ASSEMBLY
email: mikebike@rocketcar.net