Page:Practical Treatise on Milling and Milling Machines.djvu/82

76 Fig. 26

The centres swing, using three spindles, 4 inches; using the two outside spindles, 8 inches. Gear Cutting Attachment. The gear cutting attachment shown in Fig. 27 is useful for cutting spur gears of all diameters up to and including 16 inches, and is similar to ordinary index centres, only it

Fig. 27

will swing larger diameters. It is exceptionally rigid in construction and, to further insure steadiness to the gear while being cut, an adjustable rim rest is placed on the head-stock. The worm and wheel of this attachment are accurately cut, and the wheel is of much larger diameter than that of ordinary index centres; consequently the possibility for error in spacing is materially lessened. The worm and worm wheel can be disengaged and the spindle turned by hand by. means of the handle at the back, when setting or testing work.