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    Tame Tearout on the Tablesaw

    Wood is an amazing material, widely available in all sorts of colors, with beautiful grain patterns. It cuts easily with small machines and tools—products that are accessible to the home craftsman—and its strength-to-weight ratio rivals high-tech materials. But it is organic, and therefore comes with some strings attached.

    Tablesaw tearout

    Tearout from crosscutting. At the bottom and back edge of a cut, unsupported surface fibers tend to splinter away, leaving a ragged surface.

    One is movement, and there is no stopping it. The other is tearout. A budding hobbyist soon encounters splintered edges and pockmarked surfaces, damage that grows more obvious when finish is applied. It happens with almost every tool in the shop. The good news is that it can be stopped, in most cases easily.

    Tearout: Caused by unsupported wood fibers
    Tearout happens when wood is cut and its plant fibers aren’t held firmly in place. There are two main types: One happens when wood is cut across its grain, and the other when the surface is planed.

    Here’s how to avoid tearout when crosscutting on the tablesaw. It’s the easiest type of tearout to handle.

    Crosscut with no worries
    Ripping wood happens along the grain, and generally causes little to no tearout. The few long fibers involved simply shear away from each other. But crosscutting applies pressure across every fiber in a board. That’s fine through most of the cut, but near the bottom or back edge, the last few fibers have nothing behind them and would much rather splinter away than be sliced through. On most tools, there is nothing there to stop them.

    Manufacturers build those tools to make both square and angled cuts, so the opening in the table or fence needs to be extra large to allow the blade to be tilted. Carpenters don’t mind, because tearout doesn’t matter on framing, and they usually can hide the bottom side of a trim- or deck board. But furniture makers can’t always hide a splintered edge, and they quickly learn to close up that big gap with a “zero-clearance” plate, usually just a piece of plywood tacked or clamped onto the tool.

    The secret? A zero-clearance plate
    The principle is always the same: The blank plate is attached, and the sawblade is used to cut a kerf through it. (See photo at the top of this post). Then, when wood is crosscut on top or in front of that plate, the lower or back edge is supported completely on both sides of the blade. Granted, that plate will need to come off or be replaced for angled cuts, but most cuts are at 90°.

    On tablesaws, you should replace the throat plate (the one with the big slot) with a blank plywood one for all square cuts (See Fundamentals: “Get safer, cleaner cuts on your tablesaw,” FWW #200).

    Sacrificial material for the miter gauge fence too
    But you can use a zero-clearance plate on the miter gauge fence, too, to support the back edge of the cut. This is nothing more than some plywood or MDF (medium-density fiberboard) screwed to the existing fence.

    Sacrificial fence

    Add support to your miter gauge, too. A hardwood or MDF fence screwed to the front of the miter gauge will prevent the wood from splintering at the rear of the cut.

    The same goes for any crosscut sled you build for the saw
    You can tape or tack sacrificial surfaces onto the base and the fence.

    Crosscut sled

    Zero-clearance also works on sleds. Clamp a piece of ¾ -in. MDF to the fence and tack down a sheet of ¼ -in. plywood. Then cut a new slot to match the crosscut or dado you plan to make.

    Don’t use thick pieces on the base; you’ll steal too much of the blade’s height capacity. Later, when the zero-clearance slots on these plates get beat up by angled cuts or different-size blades, you just attach new ones.

    Photos: Steve Scott

    Excerpt from Christiana’s March/April 2010 (FWW #211) article “How woodworkers tame tearout”.