Electronic Design

What's All This Drilling Stuff, Anyhow?

I had planned on drilling holes in some small strips of wood—pilot holes for brads. But I couldn't find my best small drills. I was annoyed with myself. Then I realized that I didn't have go out and buy a drill bit of exactly the right size. I would just take a piece of steel wire and clip it off to make a drill bit of the correct size for the hole I needed.

I started with a short piece of an ordinary 1-1/4-in. paper clip, then drilled a hole in the wood. But the hole was too small—perhaps 0.034 in. So I took a hammer and hammered the end of the wire to make it a bit flatter and wider. The hole size then seemed okay—about 0.044 in. I drilled several dozen holes. The brads fit in okay, and I drove them in later. So I really have some flexibility in making drills of various sizes.

One of my favorite "specialized" drill bits is a piece of coat-hanger wire. I can start to drill through a floor with any ordinary, small drill bit. When it hits the bottom, I swap in a 6-in. piece of coat-hanger wire. If that doesn't go through, I extend it to 10 in., or more, as needed.

I have never been stumped. This hole is adequate for a couple of 22-gauge wires and useful for many household tasks, including phone wires, or a short run of speaker cable. After I have made a pilot hole, if I need a bigger hole, I hammer and peen the tip of that "drill bit" wider, to make a hole as large as 0.2 in., or more, as required.

Many different drilling techniques are applicable. After drilling a pilot hole through from the top of the floor, I can go back from the bottom and drill up, as needed. Or, I can drill through a wall that's 10 in. thick with a 3-in. long drill and an unlimited supply of coat-hanger wire, as I did recently. Go ahead and call me a cheater, but don't expect to stump me. Good engineers know how to solve problems with available tools.

Of course, these techniques work best on materials like wood or soft metal—not on steel. (Yes, I have good drills 4 or 6 in. long. But those are large in diameter, and I usually want just a small hole through the floor or wall.)

Sometimes people write in and ask me, "What does THIS column have to do with Analog Stuff?" Well, in this case I'm making an analog drill size, not just a digital drill size that you select from a discrete number of available sizes.

I'm still annoyed that I can't buy a light, high-rpm "1/4-in." electric drill. In the last four years, I have travelled in 24 countries, looking for 1/4-in. drills. No hardware stores, mail-order stores, or e-stores sell them. Don't try to tell me that 3/8-in. drills are "better," because they're heavier, bulkier, slower, and their chucks won't hold 0.034-in. drill bits. Maybe I'll just send off that letter to the Attorney General, complaining about the conspiracy....

A long time ago (at least 35 years), I read in some "Mechanical Design" magazine an article that praised the design of a little hand drill, which had new high-tech plastic gears. I looked closely at the picture and frowned. I went to my toolbox and dragged up the miserable, cheap, junky hand drill that I had recently bought. Yes, it was the same drill. The cheap, flimsy plastic gears didn't stay engaged. Even when the gears turned, the chuck might stop because the gear wasn't secure on its shaft. Plus, the friction was lousy. What a piece of junk, yet the magazine article bragged about its neat design.

One guy recently wrote about a problem he had shutting off his electric drill in case of a bind. If the drill grabbed and the workpiece started to spin around or rise up, he wondered why his right hand would work so poorly at letting go of the power switch. But when drilling with his left hand, he could easily turn off power. He thought my idea of using my stronger right hand to control my bike's front brakes was a bad idea and that he could let go of the brakes better with his left hand. He suspected that it's a left-brain/right-brain kind of problem.

I replied that my right index finger is well trained to let go when I want it to. So I don't have any problem letting go. Besides, when drilling difficult holes, I put the object in a drill vise, with a chunk of wood under the metal, so it won't tend to grab when it starts to drill through. (If it's important to be neat, I turn the object over and drill from the reverse side, to minimize rough edges.)

I also pointed out that when my bike's rear wheel lifts off the ground, I don't want to let go of my front brake lever. I want to servo to keep the rear wheel just barely on the ground.

Note: a bicycle is inherently neutral as to which hand you use for front-wheel braking, even if your hands are not. But an electric drill always turns the same direction when you're drilling. The extra torque (in case of a stall) may try to pull the drill out of your right hand. But it can push the drill handle toward your left hand. So maybe your left hand is better for certain kinds of drilling. Life ain't always symmetrical!

All for now. / Comments invited!
RAP / Robert A. Pease / Engineer
[email protected]—or:

Mail Stop D2597A
National Semiconductor
P.O. Box 58090
Santa Clara, CA 95052-8090

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