ox TIIK SMALL SCREW (iAUGK. 



445 



by the ends a a into a sleeve F, so that they could not be unscrewed by the 

 forces employed in the test. On the ends It h were placed brass nuts B B, 

 supported on steel collars C C, which rested in spherical seats in the brass 

 pieces D D. These last pieces D D were screwed into E E, the cast-iron 

 terminal blocks of the testing-machine. 



Two experiments were made in each case. 



Fin. :j. 



/ 



I I 

 oasifTow ofruut. 





1. With a steady pull on the specimens the torque required to turn 

 both screws simultaneously in their nuts was measured. This was ascer- 

 tained by means of a small spring balance acting by a lever on the hexa- 

 gonal sleeve F. 



2. The pull of the testing-machine was then steadily increased until 

 one of the screws was pulled through the nut. 



Fig. 4. 



The screwed pieces A A were turned out of tool steel, bright drawn 

 rods of clockmakers' silver steel, y diameter. The main object of the 

 experiments being to find the force required to shear the thread out of the 

 nuts B B by screws of given form, any deformation of the screw itself had 

 to be avoided. The h ends of the steel pieces were accordingly water- 

 hardened and let down to a spring temper. In the course of testing, one 

 out of each pair of steel screws broke at the point where it enteral the 



