Downloads and Support › Why Saw Blades Get Dull

    Written by Tom Begnal for Fine Woodworking Magazine©

    Like any cutting tool, a saw blade gets dull as it is used. And it can become dull for any of several reasons or some combination of them all.

    General wear -

    Wear is certainly one reason why a blade gets dull. As each tooth slices through wood, the cutting edge slowly abrades until it no longer cuts as cleanly or easily as it once did. That's why blades with carbide-tipped teeth are usually favored over high-speed steel (HSS) teeth. Carbide teeth are harder, so they don't wear as easily as blades with HSS teeth. Indeed, some manufacturers claim that teeth made from carbide can last 15 times longer than those made from HSS. Pitch is a problem. A heavy buildup of pitch on sawblade teeth can lead to poor cutting and shorter blade life.

    Pitch buildup -

    Another culprit is pitch buildup. As a blade cuts through wood, some of the resins in the wood stick to the teeth. Those resins can build up to a point that the blade can't cut as smoothly.

    Resin buildup also causes the cutting edge of each tooth to run hotter than normal. This is a particular concern for carbide-tipped blades, because each tooth is actually just a bunch of tiny grains of carbide held together by a material, called a binder, that acts like glue. When a blade runs hot, the binder begins to weaken, allowing some of the grains to break away.

    Resins can cause problems in still another way. Chemicals in some resins can react with the binder and break it down, again causing grains of carbide to disappear.

    Nails and other metal in wood -

    Because of its hardness, carbide is a great material for saw blade teeth. But that hardness comes at the cost of brittleness. Granted, brittleness isn't usually a problem when cutting wood. But when carbide teeth have unintentional run-ins with steel, the teeth come away either cracked or chipped. So be sure to remove any nails or screws from a board before cutting.

    A saw blade doesn't have to be spinning to encounter a problem. Once, while changing a blade, I chipped a carbide tooth by accidentally hitting it with the arbor-nut wrench.

    What to do -

    Because pitch buildup has the potential to be a three-way problem, it makes good sense to regularly clean off any pitch that shows up on your saw blade by cleaning it carefully with a little oven cleaner. Once it is clean, rinse, wipe dry, and coat the surface with a little WD40 to keep it rust free. Beyond that, it's mostly a matter of keeping the teeth away from nails, screws and free-swinging wrenches. (Remember, never lay a carbide tipped saw blade on a metal surface, like the top of your table saw, as it can damage the teeth.) Follow these simple tips, and in the end, your saw blade is going to enjoy a long time between visits to the resharpening shop.

Tom Begnal is an associate editor for Fine Woodworking.

Looking for more?