ship auger, tapered, multi-spur, cornering
Photo: Keate
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Special-Purpose Bits

These wood borers come in handy when you need holes that are extra big, extra long, curved, or super-precise

1. Ship Auger
Its corkscrew shape bores clean holes for pipes or wires or the rebar in landscape ties. A screw tip pulls along the single cutting edge, which is rugged enough to slice through nails and staples. Chips exit easily from the bit's hollow center. $25 for the 1-inch shown; 1/4 inch to 11/2 inch; 71/2 inches long; irwin.com
2. Tapered
Designed to drill the perfect pilot hole for wood screws, which have tapering shanks. An integral countersink digs a cone-shaped recess for the screwhead. You can adjust how much the bit projects past the countersink to suit screws of different lengths. $7 for the #12 shown; #6, #8, #10, #12 wood-screw sizes; wolfcraft.com
3. Multi-spur
Multiple cutting edges aggressively shave wood for the big holes you need to install door locks or thread pipe through framing. To muscle this bit through lumber, you'll need a corded drill (or at least an 18-volt cordless),with side handle to cope with the torque. $25 for the 29/16 shown; 1 inch to 29/16 inch; dewalt.com
4. Cornering
Sporting six separate cutting surfaces, this bit can carve a curved hole, useful for running wire or PEX tubing. Start by drilling straight into the wood at medium spee then slowly angle the bit any way you wish and let its side cutters gouge out the curve. $60 for a set of four; 5/8 to 1 inch; rockler.com

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