The following is an excerpt from Fundamentals of Sharpening (Fox Chapel Publishing, 2010). The skill of any craftsperson is based largely on the ability to create and maintain a keen edge on cutting tools. Fundamentals of Sharpening offers solid, straightforward advice on sharpening the most commonly used hand tools, from handsaws, chisels and gouges to bench planes, scrapers, and bits for braces and hand drills. This excerpt is from Chapter 2, “Maintaining Hand Tools.”
Sharpening a handsaw is a three-step operation. It begins with jointing, or filing the tips of the teeth so that they are all the same height. This is followed by setting the teeth to the correct angle. This ensures that the blade cuts straight and does not stick in the kerf. Setting involves bending the teeth alternately to each side of the blade’s centerline. The final step in the process is sharpening itself, typically with a file.
Not all handsaws are identical. The shape, spacing and set of the teeth vary according to the type of cutting the saw will perform. The spacing between teeth is usually expressed in TPI, or teeth per inch. The following describes how to sharpen ripsaws, combination saws, and Japanese and Western-style crosscut saws. Because of their very fine teeth, dovetail and tenon saws should be sent out to a professional for sharpening.
Anatomy of Saw Blades and Filing Angles
Filing Ripsaw Teeth. Ripsaws have widely spaced teeth with from five to seven teeth per inch (TPI). They also have a more pronounced set than other saws. Both features enable them to cut quickly along the grain. As shown in the Image Gallery, the leading edges of rip teeth are almost vertical. To sharpen the teeth, use a triangular mill file, drawing it straight across each tooth at a 90-degree angle to the blade axis.
Filing Combination Teeth. Combination saws are dual-purpose saws that can be used for both rip cuts and crosscuts, although they rip more slowly than a rip saw and cut more roughly than a crosscut saw. Combination teeth slope forward and backward at the same angle (about 60 degrees), and both edges are beveled. Sharpen both edges using a triangular mill file (see illustration in the Image Gallery), tilting the handle of the file down slightly.
Sharpening Crosscut Teeth. The teeth of a crosscut saw are closely spaced — eight to 12 TPI is typical — and they have very little set. Crosscut teeth feature sloped leading edges with bevels, which enable them to cut cleanly across the grain. As with ripsaws, the teeth should be sharpened with a triangular mill file. Hold the file at the same angle as the bevel, which is typically 65 degrees (see illustration).
Sharpening Japanese Crosscut Teeth. Japanese saws, which cut on the pull stroke, have tall, narrow teeth with very little set. Also, the teeth are beveled on leading and trailing edges, and on the tips. All edges should be sharpened with a feather file held at about a 60-degree angle to the blade (see illustration).
Sharpening a Handsaw
Jointing the Teeth. Mount the saw teeth-up in a vise with a wood pad on each side of the blade for protection. Install a flat mill bastard file in a commercial saw jointing jig. Hold the jig flat against the side of the blade and pass the file back and forth across the full length of the teeth (see illustration). This will flatten all of the teeth to the same height. A few passes should be sufficient.
Setting the Teeth. With the saw still in the vise, adjust a saw set to the same TPI as the blade. Starting at either end of the blade, position the first tooth that is bent away from you between the anvil and the punch block. Squeeze the handle to set the tooth (see illustration). Work your way down the length of the blade, setting all teeth that are bent away from you. Then turn the saw around in the vise and repeat the process on the remaining teeth.
Filing the Teeth. Refer to the appropriate illustration in the Image Gallery for the proper file and filing angle for the saw you are sharpening. For the crosscut saw shown at left, hold a triangular file at about a 65-degree angle to the blade with its handle tilted down slightly. As you file the teeth, work from one end of the blade to the other, filing all the teeth that are set in one direction. Then turn the saw around to sharpen the remaining teeth (see illustration).
A Bench Vise Saw Holder
Secured in a vise, this simple jig will hold a saw at a convenient height for sharpening. Make the jaws from two pieces of 1/2-inch plywood about 10 inches long and 7 inches wide. Then saw two 1/8-inch-thick strips and glue them along the inside faces of the jaws, flush with the top end; the strips will grip the saw blade. Fasten the two jaws together near the bottom end, screwing a strip of 1/8-inch plywood between them. Finally, bore a hole for a carriage bolt through the middle of the jaws and install the bolt with a washer and wing nut.
To use the jig, secure the bottom end in your vise. Loosen the wing nut, slip a saw blade between the jaws, and tighten the nut to hold the saw securely.
Shop Tip: A Saw Holder
Storing handsaws properly will both eliminate clutter and keep the tools accessible and safe from damage. This device can be used to hang a saw on a shop wall in plain view. Cut a wood scrap a little thicker than the saw handle to the same profile as the opening in the handle. Use the opening as a template, fasten the piece to the wall at a convenient height, then screw a small block with rounded ends to the piece as a turnbuckle. Make the turnbuckle shorter than the width of the handle opening, but longer than the height. Leave the screw slightly loose so that you can pivot the turnbuckle vertically to secure the saw to the wall.
Reprinted with permission from Fundamentals of Sharpening, published by Fox Chapel Publishing, 2010.