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The Woodwright's Guide: Working Wood with Wedge & Edge By Roy Underhill
Toothing Plane and Cabinet Scraper
Speaking of abrasive, I have mentioned sanding only once — not for finishing, but for the final rounding of the knuckle joint. Abrasive paper uses the sharp edges of crushed stone to scrape away tiny bits of wood. A fractured flint or a shard of glass gives a broader sharp edge to scrape with but functions in the same way. I plan to finish off with cabinet scrapers, but there’s another tool on the cabinetmaker’s bench that also scrapes, the toothing plane.
The grooved iron of the toothing plane sits almost vertically in the body. The grooves on the flat side of the iron become sharp teeth where the bevel side meets them at the edge. The irons come in coarse, medium, and fine, and the planes find work in veneering and in finishing impossible grain.
Even on the mellowest grained veneer, the toothing plane helps the glue hold. The coarse teeth leave tiny channels in both the background and the veneer to ensure that the trapped air can escape and that the glue is not all squeezed out by the veneer hammer — which just looks like one. It’s really a wooden squeegee worked along the freshly glued veneer, pushing it flat and squeezing it tight.
And when wood isn’t mellow, when it’s devil-twisted, passion-flamed stuff that glares back at you, then the toothing plane helps again. In such stuff, solid or veneer, a fine toothing plane may be the only tool that can bring it down without tearing it up. Working the finely set toothing plane in crosshatched patterns softly shreds the wood, leaving it level enough for finishing with the cabinet scraper.
Broken saw blades often live on as scrapers, but a purpose-made cabinet scraper has just the right degree of ductility to let you draw out and turn over a good hooked cutting edge. The words “draw” and “turn” are deceptive, because you create the hook by pushing the steel into shape with a rounded burnisher of even harder steel. This burnisher can be purpose-made or the polished back of a gouge, just as long as it is hard and somewhat cylindrical. Cylindrical is the trick. This shape concentrates all the strength of your arm into one tiny intersection with the scraper — a point of extreme pressure that you draw along the edge to reshape the steel as you need.
Once a scraper starts to scrape instead of shave, it needs sharpening. Sharpening the scraper takes three steps: truing the edge to 90 degrees, drawing out the burr, and turning the burr.
Clamp the scraper in the vise and draw-file the edge with a fine, flat file held squarely and pulled down its length. Follow the file with a whetstone, again keeping everything square. I find it easier to keep the scraper and the whetstone square if I leave the scraper in the vise and pull the whetstone down its length — just as when working with the file.
Now lay the scraper flat on the bench top with the edge even with the edge of the bench. Hold the scraper steady with one hand as you stroke down the very margin of the flat face with the burnisher — polishing and pushing the steel outward into a tiny burr with about eight or ten firm strokes. Give the burnisher a few licks with your tongue as you work.
Slide the scraper over the edge of the bench top so that you can now hold the burnisher vertically and stroke it down the narrow edge of the scraper to turn the burr upward. This takes about five or six strokes, as you gradually increase the angle and reduce the pressure, finishing the hooked edge with the final strokes.
You can’t see the cutting edge, but you can feel it with your fingers. More important, you can see it work. Hold the scraper in your fingers, springing it forward with your thumbs. Tilt it forward on the work and push it along. If you have to tilt it uncomfortably far forward before it bites, you’ve turned the edge a bit too much. The cabinet scraper gets very hot as you work. Walter Rose remembered the workmen’s thumbs turning red as raw meat from the heat of their work.
The same principle of the hooked cutting edge can apply to scrapers of any profile, from simple curves to compound moldings. Just remember that tilting a curved scraper forward changes its geometry, flattening its profile as you tilt. A bevel-sharpened scraper (sharpened like a chisel) will work when held at right angles to a surface, but it really is scraping and not cutting a fine shaving like a good hooked edge. The edge of a sharp scraper will give you a fine finish that may be diminished, rather than enhanced, by sanding.
Sandpaper has been around for a century or more, but so have other abrasives such as scouring rush, or Dutch reed. For thousands of years, artisans of all sorts have used sharkskin for fine finishing. Some friends managed to get some skin from dogfish, small sharks, and recommended it to me. They gave me some to try, and I stroked it lightly across my cheek to see just how sharp it was. Before I could try it on the wood, I was stopped by blood dripping on the bench. My entire cheek had been painlessly but thoroughly lacerated by a few million years of evolution.
"The Woodwright's Guide: Working Wood with Wedge & Edge" By Roy Underhill
© 2012 The University of North Carolina Press