SHEET NON-FERROUS METALS 



755 



thickness of material was used in each case. The results of one of 

 these comparison tests are shown in Fig. 2. Two other such com- 

 parisons were made incidental to the work being done to establish 

 operating technique on the Rockwell tester, but the results shown 

 here are typical. At least five readings were made on each sample 



2 4 6 8 10 



SPECIMEN NUMBER 



Fig. 2 — -Brass "Round-Robin" Series. Comparison of Rockwell and Scleroscope 



Testers. 



and the average was used in preparing these curves. It will be 

 noted that the readings on the different scleroscopes varied as much 

 as eight points from each other on cold-rolled materials. The varia- 

 tions in readings between the machines follow no apparent law, one 

 machine reading higher at one part of the scale and lower at another. 

 It will also be noted from the curves that the range of the scleroscope 



