260 



APPLIED SCIENCE 



Fig. 120), where S is the desired size, T the diameter of the tap or 

 screw, and N the number of threads per inch. 



For V thread : 



S = T 



1.733 



N 



For U. S. standard thread: 



r-i? 



N 



EXAMPLE. What is the tap size drill for a 

 thread per inch V-thread tap? 



in. diameter 10 



S = T 



1.733 



N 



1.733 

 10 



= .75 - .1733 = .5767 in. 



FIG. 121. Rivet Heads and Points. 



304. Rivets. A rivet before being driven is a simple 

 cylinder finished at one end with a head. Various forms of 

 BUTTON SMASHED __ heads are shown in Fig. 



121. The point of a rivet 

 is formed when it is 

 driven, while the rivet is 

 hot. Various forms of 

 points are shown in the 

 sketch. A tap rivet is not 

 really a rivet, but a form of screw. After being tightly 

 screwed in place and secured, the square projecting portion 

 shown in the sketch is cut off leaving a flat or flush head. 

 Tap rivets are used for connecting thin to relatively thick 

 parts. 



Questions 



1. State the advantages and disadvantages of a cut nail. 

 What causes a nail to split the wood? 



