Why Am I Always Out of 1/16-Inch Drill Bits?

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Kevin Cameron has been writing about motorcycles for nearly 50 years, first for <em>Cycle magazine</em> and, since 1992, for <em>Cycle World</em>. (Robert Martin/)

Many an adventuresome motorcyclist has decided to have a go at roadracing. And even if you’re not committed to a season of competition, there’s also the popularity of trackdays. It’ll be great! I’ll be out there, terrified by other total neophytes while terrifying them in turn. Who wouldn’t want a piece of that?

So where do we start? As our hero’s forefinger moves down the rule book’s technical requirements, he encounters the first of many hurdles: “All oil drain plugs must be safety-wired to prevent unscrewing.”

Now what? All we have to do is drill some little hole, right? How hard can that be? And so the journey through the looking glass begins.

How to Get Started Safety-wiring a Bolt

The idea behind safety wiring is simple: You pass a length of stainless steel wire (a good all-around size is 0.032-inch) through a hole drilled in the head of the fastener, fold the free lengths of wire parallel, twist them together, find someplace to attach those ends, pass one part of the wire through that point, and twist the free ends together.

The simplest way of drilling a drain bolt is to bore straight through its hex, transfixing it from the center of one flat to the center of the flat 180 degrees opposite. While this involves chewing through a lot of steel, all the drilling is perpendicular to the surface of the flat, an advantage because the 1/16-inch drill bit usual for this work is somewhat fragile.

With a center punch and hammer, engrave a dimple into the center of one of the hex-head’s flats. This dimple will prevent the drill point from wandering at the start. It’s best to do this work on a drill press, holding the bolt in a vise. No drill press? You can use an electric drill freehand, but the vise is really a necessity.

When you get to the actual drilling, apply a drop of oil, and apply enough pressure to make the drill push out chips. Stop every few millimeters of progress to withdraw the drill, clear the chips, and add more oil; this helps keep the drill bit alive.

As with any drilling operation, the critical moment comes when the drill breaks out on the far side. As you approach the exit, be ready to lighten up with the pressure and make the breakout gradual. If you don’t, the drill bit tries to take a big bite of metal right at the end. If so, the bit often breaks, leaving a short piece of hard drill bit in the hole. At this point, if your shop’s windows are open, the children next door may hear some colorful language.

What to Do With a Broken Drill Bit

Your Get Out Of Jail Free card for a broken bit? The tool kept handy by all who have ever done this work: a punch whose end has been ground down to 1/16 of an inch, so you can tap the broken piece of drill back out the way it came. I used my little punch just last week. (More than once, as a matter of fact. I had bought a bargain-price packet of ten 1/16-inch drill bits, and have only five left.) Just as the neighbor kids will learn new words, you too will quickly learn to anticipate breakout from the sound and feel of the drill speeding up. Lighten up or the bit will be broken; go gently until the hole is complete.

And rely on it—you will break drill bits. So keep them on hand. Think of them as ammunition you fire to become a marksman: Every round costs roughly one dollar, but over time, your skill accumulates.

Clean up the drilled hole’s sharp edges with a countersink, remove all the chips, and reinstall the drain bolt. The game now is to see how the twisted wire can be fastened somewhere nearby, remembering that it should be pulling the head in a clockwise (tightening) direction. Sometimes there’s a thin, finlike section you can drill to create an anchor point. Sometimes it’s the head of a nearby fastener, also drilled to receive the wire.

To make the wire pull clockwise from one of the ends of the drilled hole, you must twist the wires together for the whole distance from drain bolt to wherever you attach it. When I was starting out, I used to just hand-twist the strands, but soon found a worn-out ex-Air Force wire twister. Frustrating to use, it motivated me to buy a proper pair of safety-wire pliers. These allow you to grasp the doubled wire, lock the tool closed, and then twist the wire by pulling a built-in helix rod. The goal is to have just enough twisted wire to reach the point of attachment, with enough untwisted wire beyond that to pass through the attaching point and then be twisted to secure the wire in place.

Finally, use the tool’s narrow jaws to bend the projecting end 180 degrees at its center and back onto itself. So many of us learned this the hard way: If you don’t bend the twisted, cut-off end over as described, you will painfully impale your thumb, perhaps repeatedly. It will hurt all weekend, and more bystanders will be treated to imaginative new phrases rich with short, harsh words.

Milbar and Robinson (I believe the former bought out the latter) are common makes of safety-wire pliers. They’re not inexpensive. The Air Force and the airlines used to buy them by the thousands, but today they use mostly self-locking fasteners, making wire twisters into a low-volume specialty item.

How to Drill a Nut at an Angle

Survived your first few race outings and started to develop a taste for it? If so, you’ll eventually have to safety-wire nuts too. This changes everything: No longer can you simply drill perpendicularly into one flat of the hex head and through to the opposite side. Instead, now you must somehow drill at an angle, through an apex, from one flat to an adjacent flat. So how do you drill into a surface at an angle?

Some rely on patent jigs that clamp onto the nut and guide the drill. While these may be helpful, my initial experience with such things caused me to learn another way, which isn’t easy either. Nothing you do with 1/16-inch drill bits is easy!

Holding the nut in a vise, center-punch a flat about a quarter inch from an apex. I drill straight in with an electric hand drill, perpendicular to the surface, for about a millimeter (roughly 0.040 of an inch). Then I pull the bit out of the hole, re-angle the drill by about 30–40 degrees, and very gently drill again. I’m trying to create a secure pocket into which I can drill, at an angle where the bit will emerge on the opposite side of the apex and about 1/4 inch from it. I never change the angle of the drill while it’s turning; I pull the drill out, change the angle, and very gently begin drilling anew.

As with drilling straight through a bolt head, the riskiest moment is when the bit breaks out on the adjacent flat. In the case of this diagonal drilling, as the hole nears completion you’ll see a bump form on the adjacent flat: The eureka moment is nigh, and the tip of the bit is about to break through. Ease up, go very gently, and the bit can survive the breakout. Make sure to clean up the sharp edges of the two holes with a three-cornered machinist’s scraper.

Drilling in steel soon dulls a bit, especially these small ones. When the bit you’re using stops producing chips, replace it with a fresh one. I keep a bunch of 1/16-inch drills in a little plastic tube, top center drawer in the toolbox, topped up with regularity. If you want to go racing, they’re as essential as the fuel in your motorcycle’s tank.

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[Gerontious]

Me too. It’s a constant struggle.