Fig. 2516.
The method of using the scraper, [Fig. 2516], is shown in [Fig. 2514], which latter represents an engine cylinder. At b is shown the wooden rest or fulcrum; and at c the lever scraper operating on the ridge at the closed end of the cylinder. The lever c is worked on the pulling stroke only, and is so held that the edge presents a keen scraping tool which will cut very freely. The fulcrum b should be adjusted as closely as convenient to the work, so as to obtain good leverage for the scraper. It should be moved in its position, so that during the roughing out only the lower notches in the fulcrum are used.
A plan was lately resorted to on the White Star Line of steamships for re-boring a cylinder. The cylinder heads and piston follower were taken off; a groove was cut from the outer end of the cylinder along the bore as far and as deep as the counterboring was required to be done. The counterboring was then accomplished in the manner shown in [Fig. 2515]. The junk ring was provided with a small tool holder, such as is used upon boring bars. The tool was fastened in the holder while its cutting edge was in the groove referred to, cut as deep and as far up the cylinder as the counterboring was to be. To the junk ring was fastened, by two long bolts, a wooden lever extending above and across the cylinder. Two men walked around pushing the lever, and when the tool at each revolution arrived at the groove, a fresh cut was taken by moving the engine so as to raise the piston the necessary amount. It is obvious that the piston head may be steadied and held true in the bore of the cylinder by means of a few wooden wedges. Thus we see that in this operation the junk ring was made to serve as a boring bar head, the men furnishing the necessary rotative motion, the feed motion to the tool being obtained by advancing the piston toward the end of the cylinder where the work was being done.
The ridges which in time form at the two ends of a cylinder bore are usually removed by the hand-boring bar shown in [Fig. 2513], but they may, in cylinders of from 12 to 24 or 30 inches in diameter, be readily cut out by hand as follows:—
Fig. 2517.
Take a bar of steel 9⁄16 inch square and 3 feet 6 inches long; forge it at one end to the shape shown in [Fig. 2516], in which from a to b is the forged end. This end must then be heated along its entire length to a cherry red, and dipped vertically into cold water to harden it; after which it must be ground from a to b on all four faces square across, and as nearly of an even curve as can be ascertained by the eye. Next take a piece of hard wood—oak, for instance—about an inch thick and 3 inches wide; cut it to such a length that when placed upright its ends will wedge tightly into the counterbore of the cylinder. Into the edges of this piece of wood saw out a series of notches, making its finished appearance to be such as shown in [Fig. 2517]. The object of fitting its length tightly into the counterbore of the cylinder is as follows: If both cylinder covers are off or can be conveniently taken off, the ridge can be operated upon at each end of the cylinder; hence our piece of wood, which is merely an improvised rest to act as a fulcrum for the bar scraper shown at the top of the figure, would require to fit into the counterbore.