Fig. 11. Diagrams showing Method of Turning and Boring a Flywheel on a Double-head Mill having one Turret Head
In order to show more clearly the method of handling work of this class, the machining of a flywheel will be explained more in detail in connection with [Fig. 11], which illustrates practically the same equipment as is shown in [Figs. 9] and [10]. The successive order in which the various operations are performed is as follows: Tool a (see sketch A) rough turns the side of the rim, while tool b, which is set with its cutting edge toward the rear, rough turns the outside. The direction of the feeding movement for each tool is indicated by the arrows. When tool a has crossed the rim, it is moved over for facing the hub, as shown by the dotted lines. The side and periphery of the rim are next finished by the broad-nose finishing tools c and d (see sketch B). The feed should be increased for finishing, so that each tool will have a movement of say 1/4 or 3/8 inch per revolution of the work, and the cuts should, at least, be deep enough to remove the marks made by the roughing tools. Tool c is also used for finishing the hub as indicated by the dotted lines. After these cuts are taken, the outside of the hub and inner surface of the rim are usually turned down as far as the spokes, by using offset tools similar to the ones shown at C and D in [Fig. 7]. The corners of the rim and hub are also rounded to give the work a more finished appearance, by using a tool L.
The next operation is that of finishing the hole through the hub. The hard scale is first removed by a roughing cutter r (sketch C), which is followed by a “sizing” cutter s. The hole is then finished smooth and to the right diameter by reamer f. The bars carrying cutters r and s have extensions or “pilots” which enter a close-fitting bushing in the table, in order to steady the bar and hold it in alignment.
When the hole is finished, the wheel is turned over, so that the lower side of the rim and hub can be faced. The method of holding the casting for the final operation is shown at D. The chuck jaws are removed, and the finished side of the rim is clamped against parallels p resting on the table. The wheel is centrally located for turning this side by a plug e which is inserted in a hole in the table and fits the bore of the hub. The wheel is held by clamps which bear against the spokes. Roughing and finishing cuts are next taken over the top surface of the rim and hub and the corners are rounded, which completes the machining operations. If the rim needs to be a certain width, about the same amount of metal should be removed from each side, unless sandy spots or “blow-holes” in the casting make it necessary to take more from one side than from the other. That side of the rim which was up in the mold when the casting was made should be turned first, because the porous, spongy spots usually form on the “cope” or top side of a casting.
Fig. 12. Gisholt Mill equipped with Convex Turning Attachment