How to Use Scrapers and Parting tools
Scrapers, which date back to the earliest days of woodturning, still come in handy for modern turners in tasks as diverse as beading spindles and hollowing end-grain vessels. Here's how to use them, along with pointers about using parting tools.
Get into a few good scrapes
Unlike with a gouge or a skew, the bevel on a scraper doesn't lay against the workpiece to support the wood fibers as they are cut. So tear-out is more likely when turning spindles with a scraper.
Despite this, a scraper offers an advantage for turning spindles: The blade end can be formed to any shape, and will produce the exact pattern repeatedly, as in the case of beading scrapers, shown below. And a round-nose scraper is an effective, easy-to-use tool for hollowing end-grain turnings.
For best results, start with a sharp scraper
Sharpen square- or round-nose scrapers on a bench grinder. Position the tool rest 10° from horizontal to grind an 80º bevel on the blade. Lightly touch the tool to the wheel, and then swing a round-nose tool [Photo A], or slide a square-edge one [Photo B], against the wheel, maintaining the end contour. Some turners burnish the resulting burr with a special device for a smoother cut. To sharpen a beading scraper, hone flat across the top on a bench stone [Photo C]. Although scrapers cut better when sharpened on a grinding wheel, grinding the bevel could distort the contour.
Take a turn on a spindle with a scraper
Start by positioning the tool rest parallel to the lathe axis, slightly above the centerline. Lay the scraper blade flat on the tool rest, perpendicular to the axis of the workpiece. Raise the handle higher than the tip so the tip contacts the workpiece below the centerline [Photo D]. Then lower the handle in a smooth motion, raising the tip to make a shallow cut. Do not, however, let the handle go lower than the tip. Repeat until you reach the desired profile on the spindle.
When using a beading scraper, turn the blank (or the area on it that will be beaded) to the diameter of the top of the beads. As you form the beads, leave a small flat at the top center to be sanded away later [Photo E]. Cutting to full depth with a beading scraper almost always causes significant tear-out.
Scrape out end grain to make hollow vessels the easy way
It's hard to beat a 1⁄2 " round-nose scraper for hollowing endgrain vessels such as weed pots or goblets. The scraper is both effective and easy to control.
Chuck the workpiece and position the tool rest across the end of the piece, slightly above center. With the scraper flat on the tool rest, raise the handle enough to bring the tool tip to the centerline on the workpiece [Photo F]. Push the tool into the center of the revolving workpiece, and then swing the handle toward the back of the lathe [Photo G].
Keep the handle of the tool raised so the tip stays on the centerline. Repeat cutting from the center toward the rim until you reach the desired shape and depth. Adjust the cavity shape by sliding the tool on the rest and varying the rate at which you swing the handle.
To reduce tear-out by tilting the tool at a 45º angle on the tool rest while you swing the handle [Photo H]. Cutting at this angle is called "shear scraping."
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Grab a parting tool to form tenons or grooves, cut in to specific diameters for reference points, or, of course, separate (or part) a turning into multiple pieces. Restrict the parting tool to work where the grain runs parallel to the lathe axis.
Parting tools come with either flat or diamond-section blades, shown below. A standard 1⁄8 "-wide flat-blade parting tool fills the bill for most turners. Wider (1⁄4 " or 3⁄8 ") flat-blade tools excel at tenons, but prove more difficult to control in deep cuts. A knifelike 1⁄13 " ultrathin flat blade minimizes grain interruption for jobs such as parting off a box lid. A diamond-section blade (typically 3⁄16 " wide at the point) binds less in deep cuts.
Make it a point to part well
Sharpen a parting tool to a 45–80º total bevel angle at the tip [Photo I]. The exact angle isn't critical: A smaller angle cuts more aggressively, but a larger angle stays sharp longer. Experiment to find an angle that works best for you.
To sharpen the tool, adjust the grinder rest so the bevel rests on the wheel, stand the blade on edge on the rest, and slide it side to side. Flip the tool over and sharpen the opposite bevel until the bevels meet to form a sharp edge straight across the end. On a diamond-section tool, the bevels must meet at the widest part of the blade.
Here's the important part
With any parting tool, start by placing the tool rest parallel to the workpiece and slightly below its centerline. Stand the tool on edge on the tool rest, with its blade at a 90° angle to the workpiece. Touch the tip of the tool to the workpiece at the 10:30 position (when viewed from the tailstock) [Photo J]. Raise the handle, pivoting the tool on the rest, so the tip of the tool moves along the 10:30-to-center arc [Photo K]. Pull the tool straight back to remove it.
Continue this way until you reach the desired depth. You may have to widen the kerf to reduce friction in deep cuts. To do that, place the tool one-half its width to the waste side of your initial cut, then follow the 10:30-to-center arc as before. Alternate cuts on the left and right until you reach the desired depth.
The bedazzling bedan: It scrapes! It parts!
The French bedan can perform in much the same way as a skew chisel. "But I often use a 3⁄8 " bedan as both a parting tool and a square-nose scraper," says woodturning expert Brian Simmons.
"By maintaining a 60–70º bevel, I can use it like a parting tool to produce 3⁄8 "-wide parts and tenons—it makes long tenons really quickly—and as a square-nose scraper to cut recesses to hold bowls in a chuck," Brian says.
The trapezoidal blade section reduces friction in parting cuts, and provides clearance at the bottom left corner when scraping recesses. It's less likely to catch on the work than a 1⁄2 " square-nose scraper and, because it's 1⁄8 " thicker than most scrapers, reduces vibration.
But don't try to replace your parting tools with a bedan, Brian warns. "When making lidded boxes, for instance, a narrower part minimizes waste, and the grain lines up better," he says.