Metal Working Exercises 57 



however, is cheap and easily obtained, which cannot be claimed 

 for copper. 



A piece of tin 3|" x 7" has its two 7" edges turned up in the 

 same direction, one |", the other J", a line being scored down to 

 assist the bending. The plate is then wrapped round a broom 

 handle or similar mandrel, and shaped with a mallet into a cylin- 

 drical tube, having two projecting flanges, one ", the other J" high 

 (see Fig. 52). The larger one is now to be turned over upon the 

 smaller, a matter of some little difficulty without the tools of a tin- 

 smith, but success will be achieved by a pair of square-nosed pliers, 

 dealing with a small portion at a time, or the flange may already 

 have received its shaping before the plate was bent round. The 

 flange having been bent at right angles, it is next hammered over 

 against the edge of the anvil, and a tight joint made (Fig. 53). 



FIG. 52. FIG. 53. 



The cylinder is now transferred to the original mandrel, upon 

 which it should slip easily, and the flanges flattened with a light 

 mallet. Solder may then be run down the groove with a soldering 

 ron in order to make the joint watertight, but this should not be 

 necessary. The inlet and outlet tubes are made from 2" x i" strips 

 of tin, rolled round a lead pencil or similar mandrel, and allowed 

 to overlap |", solder being used to hold these together. 



Holes are now punched or cut in the condenser jacket (while 

 on the mandrel) somewhat smaller than the tubes, and then en- 

 larged by cutting back radially and bending up in such a way as 

 to provide flanges for the tubes, which are inserted and soldered 

 in. Trouble may be experienced in keeping the tube tightly held 

 together while soldering in, and, as an aid, the tube may be mean- 

 while wrapped with thread or fine wire, which is, of course, removed 

 when the job is finished. It is necessary to have the tubes a good 

 fit for the holes, as it should be remembered that solder is but a 

 cement, and joints should never be " moulded up " in solder except 

 with fixed purpose, in special cases (as, e.g., in dealing with lead, 

 which needs extra support). Solder will never make a badly 

 fitting joint into a sound job ; it is not meant to hide defects 



