RIVETING. 



test ; second, the diameter and pitch of the rivets ; and third, 

 the resistance to shearing per square inch of the material of 

 which the rivets are made. On this latter requirement there 

 has been no little discussion. It was formerly assumed, when 

 only iron plates and iron rivets were used, that the shearing- 

 resistance of a square inch of rivet was equal to the tensile 

 strength of a square inch of the rivet itself or of the plate. 

 That is, if we have iron of a tensile strength of 45,000 Ibs. per 

 square inch, the shearing-resistance of a square inch of rivet 

 would be 45,000 Ibs. On this assumption it would be only 

 necessary to so arrange the diameter and pitch of rivets that 



FIG. 40. SINGLE-RIVETED JOINT. 



the area of the rivet or rivets to be sheared should exactly 

 equal the net section of plate to secure a perfect joint. Later 

 experiments, together with the improvements in the manu- 

 facture of iron, and the introduction of steel, have changed 

 these conditions relatively. While the shearing-resistance of 

 the rivets per square inch has been, and even to-day is, by 

 many assumed to be 45,000 Ibs. per square inch, the assump- 

 tion has arisen, no doubt, from the fact that rivets rarely shear. 

 I have examined many exploded boilers, and the fractures 

 have almost invariably been through the solid plate or along 

 the line of rivets. It is very rare that the rivets shear. This, 

 no doubt, arises from the fact that the pitch of the rivets was 

 out of proportion to the net section of the plate. The old rule 

 seemed to be: the more rivets, the stronger joint. There 

 was, no doubt, a desire on the part of the boiler-makers to 



