I have found, what I suppose everyone has who has had much to do with gas engines, that the finish and truth of the cylinder bore, piston and rings should be the very best possible. To attain this perfection I its center, running in bearings, a shaft carrying an emery, corundum or carborundum wheel at one end and a driving pulley at the other. G is the end of a casting from the same pattern as E. The end is counter-bored to receive a machinery-steel piece slotted across the face to receive a square piece of tool steel. A set-screw holds the end piece from turning and a long steel bolt with a hole at one end and a nut at the other holds the cutting tool secured. This is used for boring. Fig. 2 shows a grinding bar to use between the centers of the lathe when the work is secured to the carriage and bored with a boring bar. It consists mainly of a gray-iron casting A with a drived fitted to it; the larger part is cored out and has a flange at the end. The core cutting through at one side in the middle, as shown, allows the grinding wheel to project. This casting is bored and the flange finished all over and then secured by three solid studs to another flange carrying a short shaft. Of course this short shaft should be re-centered and finished in perfect alinement after the studs are fitted. This shaft carries a pulley running loose, to which is secured an internal gear B, which drives a rawhide pinion secured to the shaft of the pulley C, a belt from which drives the grinding arbor. A larger view of the flange of A shows the means for adjusting the grind-

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Fig nave designed and made for my own use two different rigs to grind the bore of cylinders. Fig. 1 shows a rig for the lathe that does the work well. The drawing is not to scale, but shows the idea, and any machinist can work out the details. A is a chuck which centers and holds one end of the cylinder, the other end being centered in the revolving steady rest B. C is the revolving part of rest carrying the four jaws D, which center and hold that end of the cylinder. E is a gray-iron casting that bolts to the cross slide of the carriage and has a gib under the bar F bolted to the carriage. When set for the cut the gib can be set up, making all rigid. The casting E has through ing wheel. A easting D is turned to fit nicely the bore in A. D is bored eccentrically to receive a casting E, which carries in proper bearings the grinding-wheel arbor. These castings are made in skeleton form to save weight as much as possible. A steel piece F is fastened to the flange and in it slides a steel piece G that fits into a counter bore in E, the grinding arbor passing through it. A tangent screw is provided for fine adjustment. The construction and use of it is too obvious to need any further description. A bearing H is secured to the bed of the lathe and adjusted to relieve the center of any belt pull. J. S. Rounce in "American Machinist."

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