12 Tips for Drilling Holes in Metal
For most do-it-yourselfers, there will likely come a time when you’ll have to drill a hole through a piece of metal. The tools and methods used to do it are almost as varied as the different types of metals out there. Here are 12 tips to make the task fast, easy and safe.
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.