Fig. 19. Tool Equipment for Machining Worm Gear Blanks—Davis Turret Lathe
Turning Worm-gear Blanks in Turret Lathe.—This is a second operation, the hub of worm-gear blank G ([Fig. 19]) having previously been bored, reamed, and faced on the rear side. The casting is mounted upon a close-fitting arbor attached to a plate bolted to the faceplate of the lathe, and is driven by two pins which engage holes on the rear side. The rim is first rough-turned by a tool A which operates on top, and the side is rough-faced by a toothed or serrated cutter B. A similar tool-holder having a tool C and a smooth cutter D is then used to turn the rim to the required diameter and finish the side. The end of the hub is faced by cutters mounted in the end of bars E and F, one being the roughing cutter and the other the finishing cutter. The work arbor projects beyond the hub, as will be seen, and forms a pilot that steadies these cutter bars. The curved rim of the gear is turned to the required radius (preparatory to gashing and bobbing the worm-wheel teeth) by a formed tool H held on the cross-slide.
Fig. 20. Turning Bevel Gear Blanks in Davis Turret Lathe—First Operation
Turning Bevel Gear Blanks.—[Fig. 20] shows a plan view of the tools used for the first turning operation on bevel gear blanks (these gears are used for driving drill press spindles). The cored hole is beveled true at the end by flat drill A to form a true starting surface for the three-fluted drill B which follows. The hole is bored close to the required size by a tool (not shown) held in the end of bar C, and it is finished by reamer D. The cylindrical end of the gear blank or hub is rough-and finish-turned by tools held in holders E and F, respectively. (These holders were made to set at an angle of 45 degrees, instead of being directly over the work, as usual, so that the cutters would be in view when setting up the machine.) It will be noted that the chuck is equipped with special jaws which fit the beveled part of the casting.