104 



UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



the top of the wooden block, and to sort them into boxes according to 

 the position in the slot where they come to rest. The nearer we place 

 the lines the more grades of cuttings we will have and the less varia- 

 tion there will be in each grade. Fig. 6 shows the various positions 

 of the lines to make four, five, or six grades of the cuttings between 

 14 and % inch in diameter. To construct the grader the only measure- 

 ments needed are the length from a to e (1 inches) and the width at e 

 (1/2 inch) and at a (^ inch). 



The scale can be cut with a chisel on the block and the place of the 

 lines determined with sufficient accuracy by means of a rule showing 

 tenths of an inch. The distances between the lines of the three scales 

 have been calculated in such a way that each size bears a certain ratio 

 to the one next to it. The ratios used are .8409, .8705, and .8909, 

 respectively. This means that if we use the first scale each grade of 

 cuttings will average almost exactly five sixths of the diameter of the 

 next larger size. With the second scale the difference will be seven 

 eighths, and with the third eight ninths. Or, looking at it another 

 way, it means that the cuttings in one grade will not vary more than 

 as 5 : 6 in the first case, 7 : 8 in the second, and 8 : 9 in the third. 



The following table shows the average diameters of the several 

 grades (see Fig 6) : 



If the grader is used according to the directions given below the 

 cuttings will be sorted, if scale I is used, into six sizes. The largest of 

 these will be over % inch and the smallest under % i nc h 5 these should 

 be rejected. The intermediate will then fall into four sizes, which will 

 have the following diameters indicated in the table : 



Average Extreme 



Diameter. Variation. 



Size 2 2736 in. .0473 



Size 3 3254 in. .0562 



Size 4 3870 in. .0670 



Size 5 4603m. .0795 



These sizes differ from each other in such a way that the average 

 diameter of each is almost exactly five sixths of that of the next larger 



