PROBLEMS IX Dr.]rENSIO\S AND TOLERANCES 



183 



setting tolerances then becomes one of distributing certain tolerances over 

 various dimensions and different parts. This is a very difficult problem 

 and in the case of any individual tolerance a larger value does not neces- 

 sarily mean lower apparatus cost and may even mean the reverse. 



0.0006 



o.ooio" 



0.0016" 



^ DRILL ROD 



1.5 2.0 2.5 3.0 



STOCK DIAMETER IN INCHES 



Fig. 1 — Total diameter tolerances of commercial round stock 



This is easily demonstrated in the case of part tolerances on dimensions 

 which correspond to the dimensions of raw materials. Figure 1 shows the 

 tolerances of commercial grades of round stock. If, for example, engineer- 

 ing requirements dictate the use of a particular material there is no gain in 

 specifying larger tolerances than those to which it is regularly furnished and 

 doing so may require greater accuracy in the mating part. There may even 

 be economy in the use of higher priced material produced to closer toler- 



