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Page:Popular Science Monthly Volume 89.djvu/478

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��Popular Science Muuthly

��diameter of the horing-bar illustrated. A three-arm spider tastinp; having a substantial boss was bored out to be an easy runnintj fit on the intermediate diameter of the boring-bar. This was securely held against the cylinder base- flange by means of clamping straps. It is held away from the base-Hange by tubular spacers while the clamping straps were separated at the top by

hardwood spacer

blocks. The boring tool was a special iron casting having an inserted cutting tool made of tool steel. The cutter was held in place l)y a set-.screw and was inserted in a drill hole made to re- ceive it. The bor- ing tool was .se- curely clamped to the intermediate portion of the bor- ing-bar by a set-screw, was made to smooth

��cylinder and the boring-bar guide se- curely clam[)ed thereto, it will be appar- ent that the boring-bar center line had to coincide with that of the cylinder.

The cutting tool is set for the desired depth of cut, leaving about 1/64 in. of stock on a side to be removed with the reamer. The lathe is started on the back gears and the cylinder-block is moved back slowly to meet the cutting tool by moving the tool




���Boring-Bar Guide and Method of Fasten- ing It with Clamps

��A special reamer the cylinder after the boring cut was completed. This was made of a tool steel disk having sixteen cutting teeth milled on it and forced on a cast-iron bushing which was a good fit on the boring-bar. The boring-bar was machined from a piece of machinery steel \]A. in. in diameter.

In assembling the parts, the first step was to put the centering disk into the cylinder interior and then locate the cylinder carriers and boring-bar guides. The centering disk was an easy push fit in the cylinder interior and, of course, held the boring-bar in the center. When the cylinder carrier was clanipcd to the base flange of the cylinder-block, and the centering disk was backed out and its place taken by the boring tool, the cut started straight. Absolute parallelism of the boring-bar with the cylinder walls was secured by i)utling the centering disk at the head end of the cylinder and then adjusting thi' centering fi.xture screwed into the core jjrint hole so that the guide ring would supfKjrl the head end of the cylinder properly on the small diameter of the l)()ring-bar. After the centering disk had been moved to the open i-nd of the

��to finish the job.

��post carnage with the hand feed. As soon as the cut is started the power feed is adjustecl for a fine cut and the regular feed screw is used to bring the cylinder casting down. Only one cut is taken with thecutting tool, this being afterwards re- moved and the reamer substituted As the cylinder-block floats on the boring-bar and as the guide members must be accurately located initially by the centering disk provided, the new bore nmst lie true to size and the walls parallel to the center line of the cylinder.

It took about ten hours to bore and ream four cylinders or one cylinder- block. The setting up and locating took about two hours while the cutting occu- pied the remainder of the time. The cyliiuicr flange rested on the ways of the lathe, this resisting the tendency of the cutting tool to turn the cylinder casting about the boring-bar. The weight of the casting was enough to prevent any N'ibration or chattering due to movement of the cylinders. In doing a job of this kind it is essential that the cylinder be accurately located on the boring-bar. Till' guiile bearings should be thoroughly oiled and should lie a goixl sliding fit on the arbor without ha\lng any vertical movement or shake. Tlu' boring tool should bi' carefully sharpened and it is absolutely essential it be fed in slowly, so that only a fine cut will be taken. There is no necessity of blocking up the cylinder casting as this is ade- (|iiately supjxMted.- John B.Maynard.

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