54 Laboratory Arts 



accurately bent into shape, and it will be found useful to have a 

 small piece of iron rod " square filed to square edges, upon which 

 to shape the box in case of difficulty. 



Having bent the flanges into shape, and made up the box, paint 

 a little zinc chloride solution on each joint, taking care that it runs 

 well into the various joints, and by means of a hot, well-tinned 

 soldering iron, stroke the joints in turn, supplying solder in the 

 form of a strip when necessary. Do not use too much solder. 

 There will be endless trouble in making a neat joint if too much 

 be used, and if the soldering iron has already one small bubble or 

 bead of melted solder upon it, and is used sufficiently hot, this will 

 be enough to complete the box. 



Before the solder completely sets, in each case, the joint may 

 be squeezed by pliers, and so held till cold (meanwhile proceeding 

 to the second joint), from which it will be gathered that method (2) 

 will make the neater job. 



The box should be washed well in boiling water, shaped if 

 necessary on the iron plug as above, and tested by weighing empty, 

 and full of water. If the box is correctly made, the difference 

 will be 16*4 grams. 



A subsequent useful exercise may be the making of a i c.c. box. 



EXERCISE 3. Three-way plug-key. 



The base for this instrument has already been prepared (see 

 Woodwork, Exercise 2), and we are thus provided with a vulcanite 

 plate, mounted on teak of suitable size for our work. 



Take a strip of brass, " x J" section, 5" long. Cut this with a 

 hack saw into three pieces, one 2" long, and two i" long. Face 

 up these pieces, and solder them together as shown in the sketch. 

 Drill * two J" holes in the centre of the soldered pieces at XX, 

 resting the material meanwhile on a spare piece of wood, in which 

 nails may be driven to hold the brass in place. Drill also two " 

 holes in the long piece as indicated at AA, Fig. 49, and one similar 

 one in each of the smaller pieces, J" from the end, in every case. 

 Also a J" hole in the centre of the 2" piece. Underneath the 

 brasses, at points BB, i" from the free ends, drill a T V hole three- 

 sixteenths of an inch deep, and into these solder \" pieces of brass 

 wire, well straightened to form " steady pins" when mounting. 

 Two further |" holes, \" from the soldered ends, may also be drilled. 



1 Drilling must always be preceded by marking with a dot punch or 

 centre punch, in order that the drill may enter where it is intended to. 



