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. 



WI< JJM «/'WI. 



The Various Parts of Fixtures Used in Boring Out a 

 Cylinder on a 14-inch Engine Lathe 



463 



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 



