174 Materials and Their Handling 



cceding with the next operation. This is done to 

 detect the bad work, if there is any, before doing 

 anything further on the piece. 



d. Piece inspection. Done by inspectors of 

 the finished part before it is sent to the assembling 

 room. 



e. Selective inspection. This is often used 

 where the pieces are simple and made in great 

 quantities under conditions where defects can creep 

 in only slowly, as, for instance, from gradual 

 wear of tools. To inspect every piece would add 

 greatly to the cost of production. In such cases, 

 one out of a certain lot or number may be in- 

 spected. If this passes, the rest are assumed to be 

 correct. If it does not pass, others are inspected 

 and, if a certain number are found to be incor- 

 rect, the whole lot is rejected or given a 100 per 

 cent inspection. 



f. Unit-assembly inspection. Done in the as- 

 sembling room to make sure that the parts of a 

 certain definite unit, as, for instance, a typewriter 

 carriage or a lathe head, are in proper relation- 

 ship to one another. 



g. Performance inspection. Done by inspect- 

 ors, on the performance of the machine as a whole. 



Methods of Inspection. Where the pieces are 

 small and easily transported, it may be found de- 

 sirable to have the inspectors in a separate room 

 where they can do their work quietly, with every 

 convenience for the work in hand. In other cases, 

 it works out best to have the inspector on the floor 



