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From the pages of Fine Woodworking magazine Why Tablesaw Blades Get Dull Identifying the common culprits can help you postpone your next trip to the resharpening shop Editor's note: In the March/April 2002 issue of Fine Woodworking (#155), we test 14 top-of-the-line combination tablesaw blades Cuts made by the blades were checked for smoothness on a high-tech machine -- a surface roughness and profiling system -- that measures surface smoothness. Then, using the machine readings, the blades were rated as excellent, very good, good, and fair. The results, as well as more on our testing method, can be found in "10-in. Combination Tablesaw Blades" on pp. 32-37. Like any cutting tool, a tablesaw 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.
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 tablesaw-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 tablesaw 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 sawblade. Beyond that, it's mostly a matter of keeping the teeth away from nails, screws and free-swinging wrenches. In the end, your blade is going to enjoy a long time between visits to the resharpening shop.
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