968 Transactions of the American Institute. 



it is frequently performed, be called, tearing, the rivet holes with a 

 tapering punch considerably smaller than the die, always strains, and 

 sometimes fractures the iron between the rivet holes ; and bending a 

 plate, while cold, leaves the exterior of the curve in a state of tension, 

 and the interior is, by the same operation, compressed, both which 

 conditions tend to diminish their strength, and should, therefore, be 

 avoided. 



Besides the injury caused by wretched punching and cold bending, 

 the rivet holes in the inner and outer plates seldom agree, and they 

 are enlarged to admit the rivets by, what Chief Engineer Sewell, of the 

 U. S. navy, calls, with more force than elegance, " that damnable steel 

 drift pin." By the use of this the iron between the rivet holes is 

 still further weakened and burrs are raised at the sides of the holes, 

 which render it difficult to bring the plates into sufficiently close con- 

 tact to form a tight joint ; and, even after the riveting is completed, 

 careless workmen will frequently cut deep grooves in the plates while 

 chipping the seams, preparatory to calking them. 



These are some of the prominent causes which lead to the produc- 

 duction of weak boilers, some of which must, from time to time, 

 explode, if worked with steam at pressures which are very common, 

 and are keld by many to be safe~and economical. 



The writer's opinion of good workmanship, in boiler making, may 

 be learned from. the account given, in "London Engineering," vol- 

 ume III, page 10, of Mr. D. Adamson's boiler works at Newton 

 Moor, near Manchester, England. There " each plate is ordered from 

 the mill two inches longer and wider than wanted for the boiler, so 

 as to give a margin of one inch at each side, which is cut off by a 

 sheering machine, and is made use of for testing the quality of the 

 plate. This plan has the advantage of removing the rough ends of 

 the plates, and, at the same time, avoiding the use of those portions 

 which are always most likely to contain flaws, impurities or irregu- 

 larities, for forming the rivet-seams of the boiler. The strips removed 

 by the shears, which are justly considered to be inferior portions of 

 the plate, are, as we have said, used for testing the quality. Each 

 strip is bent by cold hammering, and is expected to stand doubling up 

 until the ends nearly touch each other, without showing any cracks or 

 fractures ; and all plates which fail under this test are rejected. As 

 a rule, the Bessemer steel plates stand more than this, allowing of 

 being doubled up quite close without the slightest signs of fracture, 

 •x- * -:<- % With boiler plates, particularly with those of steel, the 

 process of annealing is of the utmost importance. 



