64 



THE i\IICIlOSCOPE 



Grinding 

 and polishing 

 specimens. 



Grinding 

 and 



polishing 

 machine. 



m 



and about 1 inch diameter. Lay one of these at each end of a 

 3x1 glass slip, and lay the metal specimen face downwards 



on the glass slip in the space be- 

 ' tween the two pieces of wood. 

 Take another 3x1 slip with a 



lump of wax adhering to the 



Y^Q 66 centre, and, holding it with the 



wax downwards, press it down 

 upon the wooden plates until it is in contact with them ; the wax 

 will adhere to the metal specimen and cement it to the upper 

 slip. This can now be removed and turned over, and the speci- 

 men is ready for examination (see Fig. 66). 



The grinding and polishing is generally done on a machine 

 with a horizontal revolving disc with carborundum and emery, 

 and polished on the same machine with rouge or diamantine. The 

 following describes 

 a special machine 

 made for the 

 purpose which is 

 driven with an 

 electrometer from 

 the ordinary light- 

 ing circuit. 



It is com- 

 plete and self- 

 contained, and 

 only requires to 



be connected with the electric current supply by the usual fittings 

 to be ready for immediate use. 



Fig. 67 gives a general view of the machine, which consists of a 

 vertical spindle carrying a grinding or polishing disc, driven by 

 a small electric motor. 



The machine consists of a vertical spindle (A) carrying a 

 grinding or polishing disc (B) driven by a small electric motor (L), 

 and gives in a compact, convenient form all that is required for 



preparing metal specimens 

 for examination. 



The spindle (A) is made 

 of steel, and is bored out 

 at the upper end to re- 

 ceive the disc upon which 

 the polishing or grinding 

 material is to be placed. 

 The lower end is hard- 

 ened to prevent undue 

 wear. This spindle is 

 with pulleys of varying 

 of a belt from the driving 



Fig. 68.— No. 1292. 



furnished with 

 diameters, and 



a speed cone (F), 

 is driven by means 



