FARM MACHINERY 193 



If the box is solid, a piece of writing paper is wrapped 

 around the shaft, or journal, to give clearance or to prevent 

 the box from being too light. This paper is held in place by 

 a cord which burns up and leaves a useful oil groove. If the 

 box be split, or made in two halves, cardboard liners should 

 be inserted between the halves, fitting against the shaft to 

 divide the babbitt. Notches may be cut in these liners to 

 let the molten metal flow from one side to the other. When 

 hardened, the metal in these notches may be broken by driv- 

 ing a cold chisel between the halves of the box. 



It is usually best that the boxes be warmed before pour- 

 ing the metal, and the metal should be hot, to insure that it 

 will fill every part of the box. The metal is usually poured in 

 through the oil hole. When the metal has hardened and the 

 box removed, the oil hole should be drilled out, and, if the box 

 is a large one, oil grooves should be cut to lead the oil away 

 from the oil hole, to insure that all parts of the bearing will 

 be covered with oil. Often an old machine, when babbitted, 

 will run like a new one, the rattle and vibration due to the lost 

 motion in the bearings being overcome. 



Adjustment of the Bearings. The proper adjustment of 

 a bearing requires much skill. If the bearing be too tight, it 

 will heat, and, if too loose, it will knock and also heat. A good 

 rule to follow is to screw the top of the box down upon paper, 

 cardboard, or metal strips (called liners) between the halves 

 of the box until the box is rigid, selecting liners of such thick- 

 ness as will make the box fit the shaft as tightly as possible, 

 yet offering no resistance to the free turning of the shaft. 



QUESTIONS 



1. Define a tool. An implement. A machine. 



2. What is meant by the efficiency of a machine? 



3. Name the elements of a machine. 



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