Sharpening Circular Saw Blades

Keep your circular saw working in top form with these step-by-step instructions for sharpening a circular saw blade right in your own workshop.
March 7, 2011
http://www.motherearthnews.com/diy/sharpening-circular-saw-blades-ze0z11zhir.aspx
Use the wrench supplied with the saw to loosen the arbor nut.


FOX CHAPEL PUBLISHING

The following is an excerpt from Fundamentals of Sharpening (Fox Chapel Publishing, 2010). You can prolong the life of your woodworking tools — and improve your efficiency and quality of carpentry — by keeping their blades well-sharpened. Fundamentals of Sharpening will guide you through honing the edges of a variety of hand tools and the blades and bits of several power tools with thorough instructions alongside detailed illustrations. This excerpt is from Chapter 3, “Sharpening Blades and Bits.” 

Changing Table Saw Blades

Removing a Blade. Working at the front of the table, unplug the machine, remove the insert, and wedge a piece of scrap wood under a blade tooth to prevent the blade from turning. Use the wrench supplied with the saw to loosen the arbor nut (see illustration in the Image Gallery). Most table saw arbors have reverse threads; the nut is loosened in a clockwise direction. Finish loosening the nut by hand, making sure it doesn’t fall into the machine. Carefully lift the blade and washer off of the arbor. A worn or damaged blade should be discarded and replaced.

Installing a Blade. Slide the blade onto the arbor with its teeth pointing in the direction of blade rotation (toward the front of the table). Insert the flange and nut and start tightening by hand. To finish tightening, grip the saw blade with a rag and use the wrench supplied with the saw (see illustration). Do not use a piece of wood as a wedge, as this could result in over-tightening the nut.

Changing Portable Circular Saw Blades

Removing a Portable Circular Saw Blade. Set the saw on its side on a work surface with the blade housing facing up. Retract the lower blade guard and, gripping the blade with a rag, loosen the arbor nut with the wrench supplied with the saw (see illustration). Remove the nut and the outer washer, then slide the blade from the arbor. As with table saw blades, carbide-tipped blades should be sent out for sharpening, but high-speed steel types can be sharpened in the shop. To install a blade, place it on the arbor with its teeth pointing in the direction of blade rotation. Install the washer and the nut, and tighten them by hand. Holding the blade with the rag, use the wrench to give the nut an additional quarter turn. Do not over-tighten.

Cleaning Those Saw Blades

Most saw blades these days consist of silicon carbide cutting teeth welded onto steel plates. Carbide is extremely hard and holds its edge for a very long time, which is a good thing because you really can’t resharpen them at home, you have to send them out to a professional saw service.

Before you do that, however, you can improve the performance of any blade by giving it a through cleaning. Take a close look – you’ll see baked-on deposits of pitch and crud on the faces and sides of the teeth.

To clean the blade, drop it into a pizza pan and soak it in mineral spirits for a half-hour. Some workers prefer a commercial pitch remover, and some advocate using oven cleaner, but ordinary mineral spirits usually softens it up enough for easy removal. Then attack the crud with a brass-bristle brush and a small sharp knife. Get it all off.

After you clean it, inspect the whole blade. In most cases, a good cleaning all you need to restore your well-used blade to near-new performance. However, carbide is brittle and you may find some chipped teeth or even missing teeth.

Some woodworkers like to touch up chipped teeth with a small, flat diamond hone. If you try that, be sure you maintain the original angles and surfaces, and don’t round over the cutting edges. Once in a while you’ll find missing teeth. While the manufacturer may be able to replace them, it’s liable to be expensive, so unless that blade cost a lot in the first place, you’re probably better off to toss it and buy a new one.  (see illustration).

Sharpening Blades

Carbide-tipped blades are best sharpened professionally, but high-speed steel models can be sharpened in the shop.

Jointing the Teeth. To sharpen the teeth of a non-carbide-tipped circular saw blade, install the blade in a commercial saw-setting jig following the manufacturer’s instructions. For the model shown, the blade teeth should be pointing counterclockwise. Install the jointing head on the jig, butting its file up against the saw teeth. Then tighten the thumbscrew until the teeth drag against the file. To joint the teeth so they are all the same length, clamp the jig in a bench vise and rotate the blade against the file clockwise (see illustration). After each rotation, tighten the thumbscrew slightly and repeat until the tip of each tooth has been filed flat.

Setting the Teeth. Remove the jointing head from the jig and install the setting head. Also remove the jig from the vise and set it on top of the bench. Adjust the head for the appropriate amount of set, or bend. Using a pin punch and ball-peen hammer, lightly strike every second tooth against the setting head (see illustration). Remove the blade and reverse the position of the setting head. Reinstall the blade with the teeth pointing in the opposite direction, and repeat for the teeth you skipped, again striking every second tooth.

Sharpening the Teeth. After the saw teeth have been jointed and set, file them using a commercial saw-sharpening jig. Mount the jig to a workbench and install the blade loosely on the jig so the blade turns. Following the manufacturer’s instructions, rotate the triangular file in the file holder and adjust the guide arm to match the required pitch and angle of the saw teeth. Starting with a tooth that is pointing to the right, file the cutting edge by sliding the file holder along the top of the jig (see illustration). Rotate the blade counterclockwise, skipping one tooth, and repeat. Sharpen all the right-pointing teeth the same way. Adjust the triangular file and the guide arm to work on the left-pointing teeth and repeat, sharpening all the teeth you skipped.


Reprinted with permission from Fundamentals of Sharpening, published by Fox Chapel Publishing, 2010.