In drilling wrought iron either water or oil is required to cool the drill, but cast iron and brass are drilled dry. Light work such as hoop-iron may be drilled dry, but the cutting edge of the drill will last longer even in light work if the drill is fed with oil or water.
Figure 50.—(1) Electric Drill-Press. A small electric motor is attached to the drill spindle. (2) Tram Points. Two steel points are fitted with thumbscrew clamps to fasten them to a long wooden bar. They are used to scribe circles too large for the compasses. (3) Ratchet-Brace. Two braces, or bitstocks, are needed. A large brace with a 6″ radius for large bits and a small brace with a 3″ or 31⁄2″ radius for small bits.
In using drill-presses, some extra attachments come in very handy, such as a screw clamp to hold short pieces of metal. Before starting the drill, a center punch is used to mark the center of the hole to be bored and to start the drill in the right spot.
Figure 51.—Twist-Drills. Round shank for the post drill and square taper shank for brace work. Brace drills are small, 1⁄4″ or less.
