Metal Working Exercises 



53 



These may be added wherever necessary, clearance pieces being 

 cut away, as required. The box is then roughly cut out, either by 

 snips or chisel ; if the latter be used, the brass must be supported 

 on some heavy substance e.g. a block of iron while being cut out. 

 The roughly cut sheet is heated to redness, quenched in cold water 

 to soften it, and cut out exactly to shape. (This softening may be 

 done before the marking out of the box, if more convenient, but as 

 it usually entails making a much larger piece hot than necessary, 

 or else a waste of material by the cutting of very roughly approxi- 

 mate shapes, the sequence above given will prove, as a rule, more 

 economical). The flanges are then bent into the required shape 

 by hammering over the edge of the anvil, or by grasping the metal 

 in a vice (the flange only projecting), and hammering down flat. 



FIG. 47. 



FIG. 48. 



The edges of the box to be bent should now be scored by a scribing 

 tool (an old knife with a broken blade answers this purpose 

 admirably), on what will be the outside of the box, and the edges 

 bent as before. Previously to making the box complete, the whole 

 of the inner surfaces of the flanges, and the outer surfaces of the 

 box, should be well cleaned with emery-paper, and care should be 

 taken not to finger-mark these, or they will be difficult to solder, 

 and equally difficult to clean. 



If the plan shown in Fig. 47 be adopted, the flanges may be 

 turned on the outside of the box, by increasing the dimensions 

 of the base by the thickness of the metal on each side, in excess 

 of the geometric proportions, when scoring before bending. Simi- 

 larly if Fig. 48 be adopted, the flanges should be scored for bending 

 in a line outside the constructed squares by the thickness of the 

 material. 



Under these circumstances the box should be easily and 



