Neandernerd and his Cave of Even-Order Harmonics

I had to put the AC plug in my amp chassis today. I knew this might be a problem, since the chassis is 3/8″ thick and a bit floppy for milling. I had selected a three-prong receptacle that required a hole 1.1″ by 1/25″ in size.

I was able to use the mill to waste excess metal, but it was no good for making the contours of the hole. I tried everything I knew. Fein Multi-master. Rotary flex shaft tool. Files. Everything was slow and hard to use.

I decided to get crazy and try the drill press.

You won’t believe this. You can mill aluminum with a step bit on a drill press.

First I used the mill to reduce the thickness to 1/8″ in the applicable area. I was able to orient the chassis so I could do this easily, but orienting it so I could cut the hole was not possible.

Then I stuck a cobalt unibit in the drill press and went to town. I learned two things.

1. If you hang onto an aluminum workpiece and drag it by a unibit, it mills pretty well.

2. You can use a unibit as a very precise and quick nibbler. Seriously. You raise it a step, move the work over to it, and lower the step through the metal. I’m sure this is like #3 on just about any video of workshop no-no’s that will get you fired (right after using a lathe while wearing a grass skirt and dreadlocks), but it really works.

I only wish I had figured this out right off the bat. I could have wasted the metal with the unibit and then nibbled it to fit. I had to file the corners a little, but that was a cinch.

Here’s the obvious question: why didn’t I use a cord that only required a round hole?

Look, shut up.

Okay, I’m stupid. That’s the reason. Everyone uses computer-style receptacles these days, so I although I thought about an old-style cord, I forgot about it when I ordered the parts.

Never again. Trust me on that. An old-fashioned cord with strain relief is just as good. I think it’s better. No one is going to kick it out of your amp when they walk by.

The chassis is basically done. I have to drill a couple of round holes and get wood screws to hold everything down, but that’s it. Now it’s just a matter of soldering, adding knobs, adding a structure to protect the tubes, and turning it on.

I’m dead-set on wood screws. They won’t vibrate off like machine screws with nuts. They hold really well. And if I use short ones, they won’t protrude into the chassis and aggravate me like machine screws. And no nuts to fool with! I hate turning a screw with one hand and holding a slippery nut with the other.

I should have finished the amp today, but Mr. Amp Genius had to have his three-prong receptacle.

My mill is driving me nuts. The power feed failed, so I have to turn the dials by hand, and they’re getting so you really have to apply pressure to make them engage. Tips would be appreciated. There are nuts at the ends of the screws that–I think–may adjust this. I plan to crawl around under the table and see.

That’s the weekend! Yeah, dawg!

I can’t help it.