PASSAGE FOR OIL

Timaru Herald, Volume CXXV, Issue 18459, 28 December 1929, Page 14

PASSAGE FOR OIL

HIGH PRESSURE SYSTEM. DRILLING CONNECTING RODS. Drilling a hole one-eighth of an inch in diameter through the entire length of a nine-inch iron rod is one of the precision operations required in manufacturing the lubrication system of an American six. This long but tiny hole permits oil to be forced upward through the connecting rod to the piston pin.

Engineers not only had to find ways of performing such operations, but the methods had to be such that could be used in quantity production and with out adding a prohibitive amount to the cost of manufacture.

To drill a hole through the length of the connecting rods, drills had to be more than nine inches long, they had to be hollow to permit a flow of oil to lubricate and cool the cutting edge, and some method had to be devised to remove the chips of metal created by the drilling.

The drills have a hole 3-64th of an inch in diameter running through their centre, and a V-shaped flute cut in one side the entire length of the drill. Oil is forced through the centre hole under 500 pounds pressure, and after performing its lubricating and cooling functions, the oil returns down the flute carrying with it the metal chips The cutting edge of the drill is ground off centre so as not to interfere with the oil hole, and for that reason the drill has to be made in two pieces with the cutting point welded to the shank. Usually in drilling operations the drill is rotated. In drilling connecting rods, however, this was found impractical as the long thin and hollow drills broke when rotated at speeds up to 3000 revolutions a minute, so machines were devised whereby the drills are stationary and the connecting rods are rotated.

These specially designed machines are absolutely accurate, and are so efficiently constructed that only one man is required to keep six drills in constant motion.

With these rifle drilled connecting rods, oil is forced from the pump up through the crankshaft to all main bearings, and from these up through the connecting rods to the piston pins. Camshaft bearings are lubricated in the same manner, giving full pressure lubrication, which has long been considered a mark of quality in fine automobile engines.