Glass Working Cutting, Grinding, and Drilling 77 



1. Using a china drill. 



2. Using a ground file. 



In either case the cutting tool will be the sam 

 point of a rat-tail file, ground 

 upon a wet grindstone to the 

 shape of a triangular based 

 pyramid. 



Such a cutting tool may 

 either be mounted in the chuck 

 of a china drill, or be used 

 without breaking off the file 

 by bowing. 



A china drill is run by the 

 inertia imparted to a heavy 

 wheel near the work, and 

 mounted on a long spindle, 

 carrying the chuck at the wheel 



-the 



urn 



FIG. 67. Hollow glass spectromete 

 cell, built up of plate glass. 



end, and connected with a sliding cross-bar of wood by means 



of a leather thong (see Fig. 68). Upon the downward stroke 



sufficient energy is given to the wheel to 



enable it to wind up the leather thongs and 



raise the cross-bar. Many forms of this 



tool are known, and it is not necessary to 



describe the management of the tool further. 



Bowing is a simple method of com- 

 municating rotation to the file. The file 

 is taken from its handle, and a small hole 

 drilled part of the way through a brass 

 blank in order to permit the revolution of FIG. 68. China drill, 

 the tang of the file. A string is now 

 wrapped round the file, and attached to a bow at each end, 

 so that when the bow is moved backwards and forwards, the 

 file rotates (see Fig. 69). 



The cutting tool is entered by dipping it in camphorated 

 turpentine, and pressing firmly into the glass at the required 

 spot, twisting half round while pressing. A small piece of 

 glass is thus cut .out, which allows the point of the tool to 

 find entrance. 



