Walking down the tool aisle of a store can be an overwhelming experience. You just want to make a small hole to run some wires; why are there so many options? How do you decide what the best drill bits for the job are, so you don’t find yourself back in the same aisle two hours from now? Here’s some advice to demystify drill bits, so you know before you go.
Prep for Success
Even the best bit isn’t going to help you if your project is set up for failure, so take the necessary steps to prepare. Make sure to secure the material that you’re drilling in a vice or otherwise immobilize it. Always wear protective clothing and goggles. The base of a bit that fits into a drill or press is called the shank and will probably be either round or hexagonal. Round shanks center more reliably in the chuck, but they slip easier too. Know the size shank that your drill chuck will accommodate. If you need a bigger hole drilled, you might need a drill press, because bigger bits require more torque to spin them. Presses provide much more torque than cordless tools, can drill more slowly and if they get stuck in the process of drilling, the kickback won’t break your wrist.
The most important consideration in choosing a bit is the type of material you’re drilling through.
Bits for drilling metal fall into basically two subcategories: those for soft metals (like aluminum) and hard metals (like steel). Harder metals require stronger bits made of materials like cobalt, titanium or carbide, but their hardness makes them brittle, so drill slowly. Softer metals can also be drilled with these, but, because they’re more expensive, you might just want to go with more all-purpose bits like HSS (high-speed steel). These can drill quickly and dissipate heat more efficiently. If you’re drilling a thin surface, a conical-shaped step bit is a great tool. These provide multiple diameter options in one bit and can also be used for deburring.
There are a ton of bit designs available for wood projects, depending on your needs. For simple holes, an HSS bit will get the job done. Regular steel bits work well for soft wood, but will dull quickly in the harder stuff (for that, choose a titanium coat). The feature that sets wood-drilling bits apart is called a brad — a sharp point at the end of the bit that helps hold the drill in place. Spade bits are used for larger diameter holes, but these lack the spiral flutes to carry away drilled material, so you’ll need to stop frequently to clear out debris. If your project has special requirements like creating a plug or drilling a pocket for a dowel, then you’ll need to get a more specialized bit like a plug cutter or Forstner bit, which requires a press.
Masonry and Other
Most of the bits already discussed will work just fine with fiberglass, plastic, PVC and more. However, be careful that you don’t create too much heat; take breaks to prevent melting. Bits designed to drill through concrete have a sloping tip conducive to their purpose and must have super-strong coating like carbide, otherwise you’ll get nowhere. Specialty projects like glass require specialty bits to make clean cuts and prevent shattering, so be very specific when picking these out.
Always choose a bit by material, function and size. Making the right choice not only speeds up your project, but will keep your bits sharper and reusable.
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Blair Lampe is a New York-based professional mechanic, blogger, theater technician, and speechwriter. In her downtime she enjoys backpacking wherever her boots will carry her, rock climbing, experimental theatre, a crisp rosé , and showering love on her 2001 Sierra truck.