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Tame Handplane Tearout
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.
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 happens when wood is cut and its plant fibers aren’t held firmly in place. Handplanes can create nasty tearout in wood surfaces, especially when they hit grain that changes directions.
You can often reduce tearout by reducing the size of the opening around the hole of the blade. I call this the zero-clearance principle, or, more accurately, the tight-clearance principle.
How handplane tearout happens
The force of the blade tends to pry fibers upward, while the plane’s sole holds them down.
|If the mouth is set too wide, there is nothing to hold down the wood fibers, allowing cracks to travel forward, deep into the surface.|
A tighter blade opening puts the sole closer to the front of the blade and prevents the fibers from lifting during the cut.
|When the plane’s mouth is tightly set, the sole holds down the wood fibers in front of the cut. The iron shears them off cleanly.|
For the final, critical passes on a board, resharpen the blade, set it for a fine cut, and adjust the mouth to a very tight opening.
Depending on the plane, you either adjust the frog forward or adjust the toe of the sole backward to close the mouth.
|Set up the plane for a clean cut. Move the frog (blade carriage) forward to create a tight mouth opening. For fine cuts, open the mouth 1⁄64 in. to 1⁄32 in.|
And on planes with a chipbreaker, it helps to place it as close as possible to the tip of the blade, so it applies additional downward pressure on the chip as it curls it, fighting its tendency to tear upward.
Last, when tearout is unavoidable, use scrapers and/or sandpaper to work past it and produce a flawless surface.
Photos: Steve Scott. Drawings: John Teatreault
Excerpt from Christiana’s March/April 2010 Fine Woodworking article (FWW #211) “How woodworkers tame tearout”.