Page:Cassells' Carpentry and Joinery.djvu/38

22 and are a great convenience if of good quality. The Forstner auger bit (Fig. 110) is guided by its periphery instead of its centre, and consequently it will bore any arc of a circle, and can be guided in any

Fig. 107.—Centre Bit with Pin.

Fig. 108.—Centre Bit with Screw.

Fig. 109.—Anderson's Expanding Bit.

Fig. 110.—Forstner Auger Bit.

Fig. 111.—Auger.

direction regardless of grain or knots, leaving a true, polished, cylindrical hollow.

Augers.—The auger (Fig. 111) bores well in the direction of the grain of the wood, and is complete in itself. It is a steel rod, having a round eye at one end, through which a round wooden handle passes. At the other end is a spiral twist terminating in a conical screw with a sharp point. The edge of the spiral is a nicker which cuts the grain of the wood around the edge of the hollow.

Fig. 112.—Handled Steel Scraper.

Steel Scrapers.—The scraper is a thin and very hard steel plate, approximately 5 in. by 3 in., with or without a handle (see Fig. 112). Its action is really that of a cutting tool. It is used on a surface previously

Fig. 113.—Action of Steel Scraper.

made as smooth and level as the plane can make it. The scraper is so sharpened that a burr or feather is formed along its edges (see the diagram, Fig. 113). The thickness of the scraper blade, which is about $\frac {1}{32}$ in., is shown exaggerated. The edge is filed straight and flat, it is then rubbed along the oilstone to remove file marks, and finally the edge is turned and sharpened by two heavy rubs with a round steel burnisher held at an angle of about 30° with the plate.

Glasspaper.—This is the chief abrading material used in woodworking, and consists