Metal Working Exercises 55 



These holes and the two holes AA in the 2" piece should be 

 countersunk, either by using a larger drill, or by a metal counter- 

 sinking tool, resembling a wing drill, but 

 sharpened to the screw head angle. 



The metals may now be placed down 

 on the base board, their positions marked, 

 and the holes scribed round with the 

 knitting needle used in the previous exer- 

 cise, unsoldered, and thoroughly cleaned 

 and faced, about y\" being removed from 

 the tinned ends of the smaller pieces. 

 The several pieces should be finished by FIG. 49. 



"draw filing," and by rubbing on fine 



emery-paper, when they are ready for lacquering. This may con- 

 veniently be done by heating them over a bunsen until just too 

 hot to handle comfortably, dipping them into a clear solution of 

 shellac in methylated spirit, and brushing off the excess by one 

 or two strokes of a camel-hair brush. Usually they will dry 

 evenly ; if not, the process must be repeated, from the emery- 

 paper stage. The brushing must be done quickly and firmly, a 

 single stroke only should be required on each surface. When 

 quite dry, the metal may be heated again, either in an air oven 

 or over (not in) a bunsen flame, until the desired colour is reached, 

 any shade being obtainable from pale straw to black, according 

 to the temperature to which the metal is raised. Once the shellac 

 is dry it must never be touched with the fingers until " stoved " or 

 " coloured " and cooled, otherwise finger-marks will remain. 



Mounting may now be proceeded with. The vulcanite is to be 

 drilled under all the holes in the brass, and under the steady pins. 



By means of a bradawl the wood is pierced for screws under the 

 countersunk holes, and all is now mounted by means of brass 

 screws, care being taken to drive these well home, using the turn- 

 screw vertically, m order to prevent. damage to the screw head. 

 There should be a space between the large and the two smaller 

 pieces of about ^". 



The terminals have now to be fixed, and these may either be 

 made by soldering i" or |" brass blanks into round-head brass 

 screws (see Fig. 50), or bought terminals may be used, in which 

 case, however, their bases should have been soldered to the brass 

 bars before lacquering. 



Three terminals are required, one for each small piece, and one 

 for the centre of the larger piece of brass. 



Finally, the plug is to be made. For this purpose a piece of 



