Fig. 87.—Cold Chisel.
First draw 1⁄2 inch of one end to a smooth, round taper about 3⁄8 inch in diameter at the extreme end, then grind off the rough projecting edges until it is 1⁄2 inch in diameter. This end should not be cooled quickly, because it might harden somewhat, which would cause it to break easily. Starting 2 inches from the opposite end, draw the tool tapering to 1⁄8 inch thick and 1 inch wide, using the flatter on these tapered sides and edges. They should be made straight and smooth, with the edges perfectly parallel. Two views with dimensions are shown in [Fig. 87].
Grind the cutting edge of the chisel to the desired angle, then harden and temper it as follows: Heat about 2 inches of the cutting end to a dull cherry red and plunge about 1 inch of this perpendicularly into water; withdraw it about 1⁄2 inch, and keep it in motion between the first and second cooling places until the end is perfectly cold. Remove the tool and quickly polish one side with emery cloth or sandstone, watching the varying colors as they make their appearance and move toward the edge; when the dark purple or blue color entirely covers the point, thrust it into the water again and leave it there until thoroughly cooled. Regrind cautiously, protecting the temper, and test its cutting qualities on a piece of cast iron or soft steel.
103. Hot Cutter.—Figs. [88] and [89]. Punching, fullering, forging, hardening, and tempering. Material: 4 inches of 11⁄4-inch square tool steel.
Fig. 88.—Steps in Making the Hot Cutter.
Fig. 89.—Hot Cutter.
Punch and drift an eyehole 13⁄4 inches from the end, making all sides straight and smooth, as shown at a, [Fig. 88]. With a pair of 3⁄4-inch fullers, form two depressions on opposite sides 1⁄4 inch from the eye, as at b, fullering the metal to 5⁄8 inch thick. From this place draw the end tapering to 11⁄2 × 1⁄8 inch, and trim it off at a right angle to the stock, as at c. Using a hot cutter and working equally from all sides, cut the tool from the bar 11⁄4 inches from the edge of the eye. Draw the head end tapering to about 7⁄8 inch from the eye, draw the corners to form a slightly octagonal section. Remove all projecting metal so as to produce a convex head. (See [Fig. 89].) This will be referred to later as forming the head. Grind both sides of the cutting end equally to form an angle of 60 degrees, with the cutting edge parallel to the eye. Harden, and temper to a dark purple or blue.
104. Cold Cutter.—Figs. [90] and [91]. Punching, forging, hardening, and tempering. Material: 4 inches of 11⁄4-inch square tool steel.