Page:Popular Science Monthly Volume 89.djvu/477

 For Practical Workers

���Boring Cylinders with a Lathe

��THE average automobile repairman does not have a very extensive ma- chine shop outfit, yet he is often called upon to do repair work of consid- erable magnitude with very ordinary equipment. After automobile engine cylinders have been in use for a time, the cylinder bore is apt to be worn or scored from a wrist-pin loosening. The only possible method of repairing a cylinder that has depreciated to that extent is to bore it out. A job of this nature was done on a 14-in. swing lathe by the use of relatively simple and inexpensive fixtures.

The repair man had several scored cylinder castings belonging to a car that is no longer manufactured, and as there was a number of these cars in use in the vicinity it was considered more econom- ical to salvage the worn castings which were otherwise in perfect condition and have them in stock than it would be to purchase new parts. The cylinders, which were in- itially about 3^s-in. bore, were enlarged to33^-in.bore and oversize pistons and "leak proof" rings were fit- ted. The cyl- inder wail was of ample thickness to permit boring.

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���The Various Parts of Fixtures Used in Boring Out a Cylinder on a 14-inch Engine Lathe

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��The boring-bar guide used to support the open end of the cylinder block and the method of fastening this by clamps is shown in the illustration. The ar- rangement for feeding the cylinder- block by attaching it to the tool post of the lathe by means of a rod or key stock is also outlined. The other end of the key stock is clamped to the top of the cylinder and as the tool post carriage is fed down by the feed screw it is evident that the cylinder-block will also be pulled down on the boring-bar. The construction of the boring-bar and fi.x- tures may be readily determined by e.xamining the diagrams. A three-diame- ter boring-bar was used, two of the diameters being very accurately turned. The cylinders were provided with a threaded hole at the head end which was normally closed by a brass plug. This hole was furnished as a core print support when the cylinders were cast. A centering fixture was made to fit this hole.

This was a cup-shaped iron bushing having three equidistantly spaced set- screws bear- ing against a centering ring which was bored out to be a good sliding fit on the smaller

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