JOINTS AND CONNECTIONS 191 



important except in very long rivets holding several plates. The 

 action is then similar to that on a pin and is investigated simi- 

 larly. It may be advisable then to use bolts or pins. 



Rivets are much cheaper than bolts, otherwise bolts would 

 be used, for they are safe in bending and in tension as well 

 as in shear. An objection, however, to bolts is that it is 

 difficult to screw the nuts tight and keep them from becoming 

 loose under vibration. When bolts are used where rivets, if 

 used, might be in tension, means must be provided for keeping 

 the nuts tight. Even the best nut locks require frequent 

 inspection. 



The accompanying table from the Jones & Laughlin Hand 

 Book gives the value of rivets in plates of different thicknesses. 

 The values used are common and the steei handbooks all contain 

 tables for other values. 



In single shear rivets connect two plates, so there is one joint 

 on which the plates may slide, precisely like the blades of shears. 

 In double shear rivets connect together three, or more, plates 

 so there are at least two joints on which the plates may slide. 

 When three plates are used the middle plate is assumed to be 

 pulling out from between the two outer plates. 



In the table the thickness of the plates connected by rivets is 

 given together with the bearing value and the shearing value. 

 Figuring shear at 10,000 Ibs. per sq. in. the value of the rivet in 

 shear is constant, no matter what the thickness of the plate. 

 The bearing value of the plate is 20,000 Ibs. per sq. in. and a 

 comparison of the figures shows immediately when the value of 

 a rivet is determined by bearing and when by shear. 



The strength in double shear is of course just twice that in 

 single shear. The bearing on the plate is determined by the 

 thickness of a single plate, of two adjacent plates in which the 

 stresses are opposite. If two or more adjacent plates are fastened 

 together and act as one plate, then the plate thickness is the 

 combined thickness of the plates. 



In the table the strength of the ri vetted joint is determined by 

 the shearing value of the rivet above the heavy line in some of 

 the columns. Below the heavy lines the strength is fixed by the 

 bearing value of the plate. 



To determine the number of rivets to use first select the size of 

 rivet. The thickness of the plate is determined when designing 



