6 Essential Drill Bits

Good advice for boring jobs
By Jim Heavey

Woodworkers have come a long way since the days of the bit and brace. Though we may romanticize those times, limited bit options meant craftsmen often settled for holes that were “good enough.” Today, we can choose from specialized bits, many of which create clean, tear-out-free holes, and others that drill specially shaped holes, something that eluded woodworkers of long ago. These bits fit most of the needs of today’s woodworker. 

Brad-point bits. Guided by a centerpoint, these bits resist wandering. Sharp corners, or spurs, photo below, cut cleanly across the grain, eliminating tear-out and producing a hole with clean side walls. The deep flutes clear chips quickly. You’ll find these bits in diameters ranging from 18 " to 1". 

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The brad point starts the bit on target, and the spurs cut clean edges, but they leave a ridge in the bottom of a counterbore (a hole that doesn't go through a workpiece).

Forstner bits. For drilling flat-bottomed holes, overlapping holes to create mortises, or partial holes that extend off the edge of a board, use a Forstner bit. Here again, a center spur ensures an accurate start. The sharpened rim produces clean edges, and angled cutters between the spur and rim plane away waste. Because of the large shavings they create, occasionally retract the bit from the hole while drilling to clear chips and reduce the chance of the bit binding or overheating. These bits may have a smooth rim or a saw-tooth rim, photo below, and come in diameters from 316 " to 4". Use bits larger than 38 " in a drill press to control the rotational torque created by the large cutting surface. 

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Saw-tooth rims dissipate heat better than smooth rims, so larger-diameter bits typically use this design.

Taper and Countersinks. Ideal for drilling pilot holes for screws, they create a hole for the screw shank as well as a recess that allows the screw​head to sit flush with the wood surface, or be counterbored as needed. Adjust the collar around the bit up or down to match the screw length. Find bits sized to match #4–#12 screws.

Self-centering bits. The spring-loaded nose, sized to fit the screw hole on a hinge leaf, retracts when drilling, centering the pilot hole. That ensures hinge screws seat fully in the countersink in the leaf, and hinges end up where intended. Bits sized for #4, #6, and #8 screws prove most useful.

Twist bits. Wander into any woodshop and you’ll find common twist drill bits, the utility players of drilling. Available at hardware stores, this versatile bit has a 118° tip, photo below, that drills into wood, plastic, and metal. Because the cut begins at the center of the tip and moves to the outside edge, wood fibers on the periphery of a hole suffer tear-out. 

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Twist bits typically tear out most across the grain. The bottom contour of a counterbore matches the bevel of the drill-bit tip.

Spade bits. Though generally not used in furnituremaking, these bits make short work of drilling holes in construction-grade wood projects. Again, a centerpoint guides the bit, and outside spurs reduce tear-out on the edge of the hole. Find these in diameters from 14 " to 112 ". Back up the material when drilling a through-hole to reduce blow-out as the bit exits the board.

So there’s the drill. Add these bits to your workshop to open up a “hole” world full of boring possibilities. 

 

 

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