What are Spade Bits?
Spade bits are the least expensive tools for boring holes larger than 3/8-inch in diameter in wood, and though every hardware store in Canada sells spade bits, few people appreciate their full value. The ability to resharpen spade bits easily with a file or bench grinder is one example of what I mean.
Spade bits get dull when the metal wings on each side of the central point lose their crisp edges, and a dozen strokes with a flat file or a couple of seconds of contact against a spinning bench grinder is all it takes to restore all but the most mangled bits. No need to worry about carefully balancing each side of a spade bit since they spin so slowly in a drill.
2 Ways to Customize Your Spade Bits
Spade bits are inexpensive enough that they can also be modified for one-of-a-kind use. By grinding the sides of the bit evenly, for instance, it’s easy to make a spade bit smaller to create a custom-sized hole. Grind a little metal off each side, bore a test hole, then grind again if necessary. This technique is also useful for creating holes that are just right to accept tapered wooden plugs for covering screw heads. Ready-made Shaker pegs for coat racks also come from the factory with tapered tenons on the ends. By grinding the edges of a spade bit on an angle, you can create a correspondingly tapered hole that yields a much stronger connection.
Whatever your intentions, don’t let spade bits get hot while grinding. It’ll change the consistency of the metal, preventing it from holding an edge as long as it should. Grind only for a second or two, then cool the bit in water before repeating.
Got a hole to drill in close quarters? Is a regular bit too long to let you get in with a drill? Cut the shank of a spade bit shorter so the drill can fit into the space. You’ll find the metal of a spade bit too hard to cut with a hacksaw, but you can grind through the shank, then clean up the rough end before chucking the bit in a drill.
2 Ways to Regulate Hole Depth
Spade bits can be used both in a drill press or a hand-held drill, and there are two ways to regulate hole depth when you’re drilling by hand. If you only need to ballpark hole depth, then wrap a piece of electrical or masking tape around the shank. As the tape starts to flap against the wood, you know you’ve bored far enough. It’s fast and easy. When precise hole depth is crucial, cut a length of 3/4” x 3/4” softwood, then bore a hole for the shank of the spade bit along its entire length. Slip this depth block over the spade bit, chuck the bit into your drill, then adjust bit position in the chuck so the block rubs against the workpiece and the drill chuck at the depth of hole you want.
Paint Mixing: New Life for Old Spade Bits
Stain, urethane and paint all benefit from mixing before application, and while you could use a stick, power mixing with a cordless drill is much better. I reserve a retired old 1 1/2” diameter spade bit for mixing duty and it works perfectly. Reverse bit rotation a couple of times for best results.
Spade bits have a tarnish reputation with some people because they create rough holes when they’re dull. But once you learn how to keep them sharp, and how to modify them to customize hole size and shape, you’ll find no more grounds for spade bit prejudice.
Got a Question? Ask Steve Maxwell
Have you got a home repair, renovation or woodworking question? Email me and it could appear in a future column.