No Fancy Drill Bits for Metal Required
If you'll be drilling a lot of holes, or need to drill through hard, abrasive metals like stainless steel or cast iron, spend a couple bucks more for black oxide or a cobalt steel drill bit for metal. These bits will bore more holes before becoming dull. Some bits also have a special coating called titanium nitride (TiN), which manufacturers claim helps resist heat and friction better, making these bits last up to six times longer than standard high-speed steel bits.
Protect Your Eyes
It only takes one tiny metal fragment to cause a serious eye injury, so proper eye protection when drilling metal is an absolute must. For the best protection, choose safety glasses that wrap around the sides of your face.
Make a Dimple
Drill bits have a tendency to wander when you first start drilling. To prevent this, measure and mark where you want the hole and then use a center punch and hammer to create a small dimple. This gives the tip of your drill bit a place to ride in as you begin to drill.
Lubricated Bits Last Longer
For drilling holes in steel that's 1/8 in. or thicker, use cutting fluid or a multipurpose oil like 3-IN-ONE. Lubricating the bit reduces friction and heat buildup, which makes drilling easier and your bits last longer. For easier-to-drill metals like aluminum, brass or cast iron, lubrication isn't usually necessary.
Clamps Prevent Stitches
Start with a Small Hole
Deburr the Hole
After drilling a hole in metal, it's a good idea to remove any sharp edges or burrs left behind. You can buy fancy deburring tools to smooth sharp edges, but before spending money on one, try this trick: Take a twist bit slightly larger in diameter than the hole you just drilled, and gently hand-twist it over the top of the hole. This will smooth out the edge of the hole and grind away any burrs.
Hole Saws Cut Bigger Holes
For large holes, a hole saw gets the job done cleanly and quickly. Like twist bits, hole saws chuck right into your drill and will cut through thin-gauge sheet metals like aluminum and steel. Use a scrap of plywood as a backer for the hole saw's pilot bit and to protect your work surface.
Drill at a Slow Speed
Make a Sandwich
For clean, precise holes in thin sheet metal, make a wood sandwich. Simply sandwich the sheet metal between two pieces of wood and clamp everything down on a table or workbench. The wooden 'bread' layers of the sandwich keep the sheet metal flat and prevent the drill bit from wandering as it bores through the sheet metal.
Try a Step Bit
Step Up to a Drill Press
While it's fairly easy to drill most holes in metal using nothing more than a handheld drill, you'll almost always get greater accuracy and better results using a drill press. Most drill presses are actually built with metalworking in mind. Pulling down on the handle causes the bit to plunge straight down into a workpiece and make a very precise hole.
Drill presses also come with beefy cast-iron tables with tilt and height adjustments, and allow a variety of clamping options. Speed changes are as easy as opening the lid and moving a rubber belt from one pulley to another. The most expensive drill presses are floor-standing models, but you can buy a decent benchtop unit for about $100.