2o Laboratory Arts 



as the blocks are not then liable to be lost. Attachment may be 

 made either 



1. By cutting a "lug" on the block, and screwing through 

 this lug (Fig. 15), or 



2. By a strip of brass, let into the base of the block and screwed 

 into the base of the stand (Fig. 16). (See METALWORK for method 



of working brass.) 



The stand may now be 

 cleaned up with fine glass 

 paper supported on a cork 

 block, and stained maho- 

 gany colour (with " Bismarck 

 brown " dissolved in methy- 

 lated spirit), or walnut colour 

 (with " Vandyke brown " dis- 

 solved in ammonia solution), 



rIG. 15. JflG. lo. _ . . - . . , 



after which it may be sized 



with weak glue, and varnished with dark oak (inside) varnish. Or it 

 may simply be coated with a black material lampblack, shellac, and 

 methylated spirit when it is ready for the mounting of the tubes. 

 Details of the composition of these stains will be found in Section IV. 



EXERCISE 2. Teak and vulcanite base for plug key. 



The making of this will cause little trouble, the only new point 

 being in the handling of the new material. 



Materials required ': Teak, 4" x 4" x j" ; vulcanite, 3 J" x 3^" 

 X i" ; four brass countersunk screws, J" No. 6. 



Tools required ': Plane, square, turnscrew, brace, and counter- 

 sinking bit, twist drill to take screws, gimlet or bradawl, emery- 

 paper, glass-paper. 



Method: Plane up the teak to size, and mark a chamfer J" off 

 each edge. Plane this off, and glass paper the whole to a good finish. 



The vulcanite plate may not be exactly to size. It may be 

 sawn in shape by a tenon saw, and rubbed down to exact size by 

 rubbing an edge on coarse emery paper. The edges should be 

 slightly rounded, see Fig. 17, and the plate should be finished to 

 fit the top of the wooden base exactly. 



Holes are drilled in the vulcanite by means of a twist drill 

 not spoon-bit, or gimlet as these bore too quickly and would split 

 the material. The screw holes are placed at the four corners, " 

 from each edge. Countersinking may be performed either by the 

 hard-wood countersinking bit, or by a twist drill about three times 

 the diameter of that required for the screw hole. 



