In cutting spiral gears the universal milling machine is generally used, as it is provided with proper devices for rotating the gear blank at the same time that it is fed toward the cutter. The machine is provided with an indexing mechanism, and also with change gears by which any length of lead of the spiral may be obtained. In all cases of spiral gear cutting, the milling-machine table must be set at an angle, as shown in Fig. 276, the center of the cutter being directly above the point of intersection of the axes of the arbor carrying the gear blank and that upon which the cutter is mounted.

The preliminary cutting or gashing of worm gears is frequently done on a universal milling machine, on account of its adaptability to all kinds of angular work and to making feeds in all directions.

Lubrication of Cutters

In gear cutting, the lubrication of cutters is governed by the same conditions and requirements as in ordinary milling-machine work, and is governed by the material to be cut.

Types Of Gear-Cutting Machines

To familiarize the student with the special features of different types of gear-cutting machines, illustrations and descriptions are given of the machines made by some of the more prominent builders.

Whiton Gear-Cutting Machine

In Fig. 283 is shown the Whiton automatic gear-cutting machine. The cutter is carried by the spindle A, which is journaled in a saddle B, sliding upon the swinging carriage C and capable of adjustment at any angle necessary to cut bevel gears. The machine is shown arranged for cutting spur gears. The cutter arbor A is driven by the pulley D at the back of the machine, acting through a system of gears not shown. The blank to be cut is held on an arbor fitted into the vertical spindle E, and its upper end supported by a center in the arm, adjustably clamped to the column G. The traversing screw H, has a graduated dial. A gage is provided for centering the cutter; and graduated stops provide micrometer adjustments for setting over the cutter in bevel gear cutting, and for setting over the blank. At J are the change gears of the indexing mechanism.

Fig. 283. Automatic Gear-Cutting Machine Courtesy of D. E. Whiton Machine Company, New London, Connecticut.

Brown and Sharpe Gear-Cutting Machine

Fig. 284 represents a Brown and Sharpe gear-cutting machine. The gear blank is carried on an arbor fitted to the horizontal spindle A, and supported by the outer supporting bracket B. The indexing mechanism is in the rear of the indexing wheel C. The cutter is carried by the cutter spindle D, mounted in the traveling carriage E. In smaller machines the base upon which this carriage slides is pivoted so as to be set at any required angle for cutting bevel gears. The machine is entirely automatic in its action. It has an attachment for cutting internal gears.

Fig. 284. Number 6 Gear-Cutting Machine Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island.