124 



Journal of Agriculture, Victoria. 



[lo Feb., 1912. 



be I in., then the end would be upset to f in. diameter at the point. At 

 the same time, it would gradually become smaller as the distance from the 

 end increased, until the original diameter of the bolt is reached, which 

 would be where the heat does not rise sufficiently high to assume the red 

 colour. 



If the plain bar be long enough to conveniently hold in the hand 

 without burning it, the best means of upsetting it is to catch hold of the 

 cold end and hold it in a vertical position. By repeatedly raising it to 

 a good height and bringing the heated end down with as much force as 

 possible, it will become enlarged. In most cases, the bar will bend before 

 being sufficiently upset, but it can be straightened and the upsetting pro- 

 ceeded with. 



To form the scarf, the best plan is to follow each successive step 

 shown in Fig. 47, where a shows the bar upset, b with the end bent so 

 as to be conveniently struck with the hand-hammer in the direction and 

 position of the arrow, whilst c shows the shape made with the hammer, 

 as well as the fuller in its place tO' receive the first blow. As each blow 



M 



47. LENGTHENING BOLT. 



a. Bar upset. 6. End bent tor striking with hammer. c. Sliape made with hammer. Fuller 

 in position to receive the first blow. d. Effect of using fuller. e and /. Correct position for 

 hammering. 



is delivered, the fuller is moved slightly forward, leaving in its trail a 

 succession of little steps as shown at d. It should always be the object 

 of the operator to obtain the shape shown, for a bad weld is sure to follow 

 a badly formed scarf. 



Particular attention should be paid also to the manner in which the 

 pieces are laid together ; e and / show the correct position previous to 

 hammering. For welding small iron, the hand-hammer is heavy enough, 

 but the blows should be delivered as quickly as possible so that the union 

 is made complete before the temperature has fallen below the welding 

 point. If it is noticed that the weld is only partially made, then the 

 work should be returned immediately to the fire and again raised to the 

 welding heat and hammered. 



When a weld is properly made, there should be no part of the scarf 

 visible. If that is the case and the size has been maintained, then there 

 will be no reduction of strength. 



Before welding on the screwed end, the proper length should be 

 measured off, making sufficient allowance for the waste. To upset the 



