Some people like to joke that the best tool for any job is a bigger hammer. A woodworker's joinery mallet, with its massive square head, fits that description, but there's more to it than that.
A well-designed mallet is light enough to control comfortably but heavy enough to deliver useful power without requiring a wild, roundhouse swing. A mallet also offers a broader striking surface than a hammer, and one that is tailor to the nature of the work. While a carver's slender mallet allows pinpoint control and a much lighter touch, the joinery mallets broad, flat striking surface is ideal for other tasks that require more force and less flexibility.
A square-headed mallet excels at driving chisels to chop joinery, especially when cutting across the grain for dovates or mortises. It's also great for project assembly and other tasks that require a firm rap or two. Another great thing is that a mallet is easy to make.
Start with a blank of splinter-resistant hardwood such as hard maple. A block about 3 in. sq. by 41/2 in. to 5 in. long will make a mallet head that is massive and heavy enough to deliver a blow with great force when needed. You can glue up such a block if you do not have 12/4 stock available, but be aware that the glue joint might fail ever.
A through-mortise in the mallet head provides an attachment point for the handle. To make it, find and mark the center in the top of the blank. Then, using a drill press or a hand-held drill with a spade bit bore a 3/4-in. diameter hole through the blank, top to bottom. Use a rat-tail (round tapering) rasp to elongate the hole on the top of the mallet head by 1/16 in. to 1/8 in. Toward the end grain in each direction. The wider opening should taper down about halfway through the mortise. If you do not have a rasp or file, a 1/2-in. dowel and some course wallpaper will do a decent job.
Next, mark the striking surfaces of the mallet for cutting at a slight angle from top to bottom. An angled surface will strike the butt of a tool handle more squarely because the mallet itself will typically be angled slightly upward when the blow lands. Cutting the ends is simple on the bandsaw. Plane or sand away the sawmarks. It's also a good idea to bevel the edges and corners of the block to prevent splintering.
The handle also should be of a sturdy, straight-grained hardwood such as maple, birch, hickory, or oak. Start with a 12-in. length that is 3/4 in. thick by 11/4 in. wide.
Begin by marking the layout for the tenon that will connect the handle to the head. At one end, mark a centerline to bisect the width of the piece. Use this line to lay out a 3/4-in. square. Next, mark out a shoulder line 31/2 in. from the end of the piece and then cut away the waste on the bandsaw to create the square tenon. The extra 1/2 in. of tenon length will allow the tenon to protrude from the mallet head so it can be trimmed flush after glue-up.
Making a square tenon round is reliably easy if you follow the steps shown in the photos on p. 34. (Of course, if you have a lathe, you can turn the entire handle. mortise. The handle should fit snugly, but you should not have to strike it to drive the tenon all the way into the mortise.
Next, use a bandsaw or a handsaw to cut a sawkerf about 21/2 in. deep down through the center of the tenon and perpendicular to the 11/4-in. dimension. This kerf will hold the wedge that secures the handle to the mallet head. You want the wedge parallel to the striking surfaces. If it was parallel to the long grain, it could split the mallet head. Before assembling the mallet, shape the handle for a comfortable grip.
To keep a solid connection between mallet and handle, I drive a glued wedge into the kerf in the top of the handle. This expands the handle against the walls of the mortise and tightens the fit. Make the wedge 2 in. to 3 in. long, no thicker than 1/4 in. to 3/8 in.
To assemble the mallet, put a little glue on the inside of the mortar and push the handle into place, making sure it's oriented correctly to the striking surfaces. Next, apply some glue to the wedge and hammer it into the sawkerf. When the glue dries, saw off the wedge and the excess length of handle, then chisel or plane the top smooth.
Wipe on a little Watco or linseed oil for an optional finish. Avoid wax-too much will make the grip slippery.