A grinding-machine for finishing spur-gears is illustrated and described; claims are made that it will grind transmission gears on a production basis after they have been heat-treated and will produce correct tooth-contour, smooth finish and accurate tooth-spacing, these features being necessary in producing gears that are interchangeable and that run quietly.
This machine is of the generating type, its action being that of rolling a gear along an imaginary rack and using the grinding wheel as one tooth of the rack. The dished grinding-wheel is reversible, 30 in. in diameter, mounted below the gear, and can be swiveled to the right or left of the center position up to an angle of 25 deg. The work-spindle carries the indexing and the generating mechanisms at the rear, where they are accessible and yet are protected. Two or more machines can be operated simultaneously by one man, as a clocklike mechanism can be set to stop the work-carriage and the grinding wheel when the last tooth of a gear has been ground.
A drum-cam drives the work-carriage. Thin steel tapes are used to accomplish the generating principle; they wind and unwind on a pitch-diameter segment as the work-carriage is driven forward and backward, and produce uniform duplication of tooth contour. Slight variations of tooth-contour can be made easily by giving a greater or less angle to the wheel and also by varying the diameter of the pitch-circle or segment.
A machine for testing gears that have been ground is described also; it will develop the involute curve, indicate whether it is true or modified and test tooth-spacing. By means of adapters, engine-front spiral-gears and bevel-gears can be checked for accuracy of contour and for tooth-spacing.