The Technique of FURNITURE MAKING
Sharpening bits
Basic rules as laid down by Ridgway are: (1) always sharpen from the inside or underneath, never outside or on top; (2) maintain original shape and angles; (3) use suitable smooth-file, never grind and always file lightly, removing as
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70 Sharpening wood bits
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little metal as possible and preserving the balance of the bit so that each side does the same amount of work. Figure 70 gives the procedure. In 70:1, A is the side wing, B the cutters, C the spurs and D the throat. The sequence of sharpening is as follows:
Sharpening the side wings (70:2). Rest the bit in the bench with the screw lead down. File with the file working through the throat of the bit. Never file the side wings on the outside or the clearance will be ruined (the appropriate file section is shown alongside each drawing).
Sharpening the spurs (70:3). Hold the bit nose uppermost with its twist firmly against the edge of the bench. File the inside of the spurs. Never file the outside as this reduces the clearance, causing binding and clogging of the bit.
Sharpening the cutters (70:4). Hold the bit as in (70:2) and file the cutting edges on the underside only, i. e. with the file working through the throat of the bit. The cutters must be at the same level so that they cut chips of equal thickness.
Another wood-boring tool which is always abused is the common bradawl. It should be carefully sharpened with a fine file and finished on the oilstone, and is used for boring fine holes for nails or the threads of screws but not the clearance hole for the actual shank of the screw which should be made with a shell-bit or twist - drill. The birdcage-pattern bradawl with square shank bores with a reamer-like action, and can be used on the thinnest wood without splitting. Reamers for use in the arm-brace can also be obtained, and are used for widening existing holes.
Plug-cutters
Cross-grain pellets or plugs for filling screw - holes can be cut with Stanley plug-cutters, available in three sizes for Nos. 6, 8 and 10 screws. These are virtually hollow drills cutting a circular path, of which the core or waste forms the required pellet. Larger sizes cutting standard 3/8 in (9.5 mm) and 1/2 in (12.5 mm)
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71 Stanley plug-cutter
diameter plugs can be obtained for use in the drill-press or drilling machine.
