280 



SHOI 1 TKSTS. 



the angle is denoted by 0. Fig. 141 : Cold test, to bend 

 without fracture to the following angles : 



lin. plate 

 |in. 

 iin. ,, 

 Jin. 



Lengthways. 



10 to 15 deg. 

 ^0 to 25 

 30 to 35 

 55 to 70 , 



Crossways 



5 



5 to 10 

 10 to 15 

 20 to 30 



The same plan is adopted by private purchasers, and 

 in the case of both iron and steel plates and bars it is usual 

 to specify that a specimen of required size must be able 

 to stand bending back upon itself that is, through 

 180 over a bar of certain radius, generally one and a 

 half times the thickness of the plate or bar, without 

 showing any signs of cracking. In some cases specimens 

 from steel plates and bars are bent close upon them- 

 selves that is, with no internal radius of curvature at 



o 



BEFOBE. AFTEB. 



FIG. 143. DRIFTING TEST. 



the bend, without signs of cracking, Fig. 142. If the 

 specimen begins to crack at a less angle than the specified 

 one, which may not be necessarily 180, the angle at 

 which this takes place is noted and given in the report. 



146. Drifting Tests. A good test often applied to 

 rnild steel is that of drifting out a hole of specified size to 

 one much greater. When this is done, any lack of ductility 

 is at once shown by the cracking of the edges of the hole 

 so drifted. A usual drifting test is to punch or drill a 

 hole fin. diameter in a piece of the metal 4in. or Gin. 

 square, and enlarge this hole by forcing in a circular drift 

 with a ten-to-one taper until the hole has been enlarged to 

 l^in. diameter. This is seen on Fig. 143. When tested 

 under these conditions, if the metal is not sufficiently 

 ductile, either the plate will be split clean across or small 

 local cracks will appear around the edges of the hole. 



