Sharpen A Scraper...And Put It To Work: Turn a hook and watch the shavings fly.Comments (0)
This article is from Issue 67 of Woodcraft Magazine.
Turn a hook and watch the shavings fly
By Andy Rae
When smoothing wood, I reach for a rectangle of steel called a card scraper. Despite its humble appearance, a card scraper is remarkably versatile at refining surfaces. It will remove hardened glue, smooth and level difficult woods and exposed joints, and smooth a finish. Its small size makes it more maneuverable than a plane for reaching into tight spots, so you can preserve your supply of sandpaper. A scraper does it better, faster and without annoying dust.
Scrapers come in all sorts of shapes and sizes, including curved and profiled. Some can be used in specially designed planes and scraper holders. But my daily scraper is the card scraper, either thin (0.020-0.025") or thick (0.30-.0.040") depending on the job at hand. Thinner scrapers excel at delicate work, where light cuts and finesse are required. Thicker scrapers are best for heavier work: smoothing tabletops, removing milling marks, and the like. For most applications, the scraping work is done by a small hook along the working edge. With a little practice, you can use this tool to produce tiny shavings, even on hard and figured woods that show tearout when worked with a plane.
Scrapers require sharpening to work properly, and I’ll show you how this can be done with a few basic tools. You’ll need a mill file, a block of wood, medium and fine honing stones, and a round burnisher (a length of polished, hardened steel). For rough work, such as removing cured glue or cleaning grimy wood, a few strokes on a file will prepare you for scraping. For finer work, you’ll want to polish the edges to a mirror shine and then burnish four small hooked edges.
Scraper job description
Getting edges straight and square is the first step
On new or old scrapers, I use a file to establish straight and square edges and to remove any nicks or old burrs. Next, I hone the faces and edges on a 1200-grit waterstone using a simple kerfed block of wood. Then I create a mirror shine by polishing the same surfaces on an 8000-grit stone (similar-grade oilstones work, too), again using the block of wood. Total filing and honing time: About four minutes.
Burnishing creates a tiny hook you can detect with your finger
The tiny arc of steel on a scraper’s edge, called the hook, is what does all the shaving. Don’t try to maximize the size of the hook–a smaller hook will provide the best performance and a longer-lasting edge. The two steps shown here shouldn’t take more than about 20 seconds, then you’re ready to scrape! When the hook dulls, you can restore the hook once or twice by re-burnishing. When you can only produce dust rather than tiny shavings, it’s time to resharpen.
Burnish flat. A good burnisher has a polished, mirror-bright finish. Rub a little oil on the rod, and keep it flat on the scraper and slightly angled, as shown. Press downward while pushing or pulling to coax the small burr outward and to consolidate the edge.
The payoff: Super-fine shavings and superb control. Hand technique makes a difference: For an aggressive shaving, bow the scraper slightly away from you, tilt it forward 1° or 2° past 90°, and push. Firm strokes generate heat; don rubber tips (from office supply stores) to keep thumbs cool. Reverse the procedure for a pull cut. For fine shavings, use little or no bow and angle the scraper 45° or more. Scrape with the direction of the grain,
but when you can’t, such as when smoothing crotch figure or other difficult woods, no worries. Lighten your pressure and take smaller shavings. No edge tool leaves a smoother finish–with zero tearout!
Pull the hook. Hold the scraper slightly off the edge of a work surface, and angle the burnisher 1° to 3°. Using light pressure, give the edge just two or three strokes to form the hook. Pull towards you in an upward sweeping motion, letting the burnisher move off one corner; then push to the opposite corner.
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