How to Drill Correctly
Nearly everyone owns a drill, but relatively few actually know how to efficiently and safely use one. If you plan to do any restoration work on a car it's a certainty that you'll need to do plenty of drilling, so here are a few techniques and tricks.
The drill itself should be as powerful as possible. That means the greater the current requirement (amps) the more powerful it is, so don't buy one that draws less than 6 amps. Regardless of brand or model, your drill should have a 3/8ths chuck (keyless preferred) and be variable speed with reverse. It's very hard to control drilling operations without variable speed.
As for drill bits, you shouldn't skimp on quality. Cheap bits are available everywhere, but these typically dull to uselessness after one or two procedures. Wood bits (blade and Forstner) are handy around the house, but will almost never be used in automotive work. Metal-cutting bits will earn their keep for many years, so spend your money well on a good set with lots of sizes.
Metal-cutting bits are frequently advertised as "high speed steel," "twist drill," and other terms. Look instead for descriptions such as "cobalt" or "Professional grade," as a determination of quality. For comparison purposes, a 115-piece set of high-speed steel bits costs around $30 in tool catalogs, whereas the same set in cobalt will cost about $100. The high-speed set will last a while, but bits will break more easily and lose their sharpness. The cobalt set will last a lifetime.
Drill bits: A: hole saw drill; B: Forstner bit; C: Spring-loaded center punch; D: three different-sized metal bits; E: wood bit; F: masonry bit.
You need to buy one more thing, a center punch. These are spring-loaded devices that punch a "starter hole" in metal when pushed down with your hand. They are invaluable in preventing "drill bit wander" when starting to drill a hole and help to precisely locate where to drill. Add to that purchase a pair of safety glasses and you're ready to go.
Insert a bit into the drill. Push it well into the chuck and then tighten the jaws to hold the bit firmly. Smaller bits can easily bend and snap, so insert them as far as possible to minimize the length outside the chuck's jaws. Grab the center punch and push it several times into the point to be drilled to create the "starter hole."
The center punch leaves enough of an indent in the metal (in this case aluminum) to keep the drill bit from wandering as you start to drill your hole.
Good drilling requires hand-eye coordination and a fair amount of well-directed strength. It's a good idea to get into the practice of holding the drill with one hand and using the other to add pushing force, as well as directional stability. Whether you are drilling down, up or in any other direction, the name of the game is to keep the drill bit exactly 90-degrees to the piece being drilled. As a rule, the bigger the drill bit the slower the speed of the drill. You'll have to practice a little, but you'll get the feel of it pretty quickly.
Remember to keep the drill at 90 degrees to the surface being drilled. Use pressure (rather than speed) to do the cutting.
If you are drilling sheet metal all you need is a good bit and some pressure. Start the drill rotating slowly until the bit begins to chew the metal, then speed it up — all the while pushing on the drill. The drill's noise will change pitch as the bit is about to drive all the way through, so be prepared to stop. Don't put your hand behind the work piece, because you won't be able to stop the drill in time to prevent injury.
For thicker metals (1/8th inch and up) you need something to cool down the bit while it's drilling. Friction-induced heat is the enemy of drill bits, so keep an oilcan handy. When a hole is started, put a few drops of oil into it and continue drilling. The drilling will cause smoke as the oil burns, so don't be surprised. Continue adding oil periodically. This is a messy, but necessary, procedure that will keep your bits from getting prematurely dull.
- If you have to push extremely hard it's likely the bit is dull.
- For larger holes it is sometimes easier — and more accurate — to drill smaller holes first and then re-drill with larger bits.
- If your drill uses a geared key for the chuck, fasten it in some way (string, special rubber devices) to the drill's cord. Otherwise, you will lose it.
- If using an extension cord, make sure it is heavy-duty enough to carry proper amperage to the drill.