REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1903 169 



The finest of the numepous grades are again rewashed and 

 -orted by what is known as the elutriation process. The 

 powders are suspended in water and forced through a set of 

 tanks or cylinders, each 3 feet high and varying from 3 inches to 

 40 inches in diameter. That portion of the material that can no 

 longer be supported by the decreasing strength of the current as 

 it. passes from the smallest to the largest tank, settles to the 

 bottom and is afterward drawn off. Any impurities that may 

 have passed through the first cleaning process pass out with 

 the surplus water. The powders thus obtained are dried and 

 are then ready for market.^ 



In this condition the emery is purchased by the manufacturers 

 of emery products, who make it up in wheels, stones, emery 

 paper, emery cloth, etc. 



The wheels are made by binding the grains with some cement- 

 ing material. Celluloid, rubber, silicious and vitreous bonds 

 are used, each being specially adapted to certain classes of work. 

 The required amounts of emery and bond are carefully measured 

 out, thoroughly mixed, tamped into a mold and put in a kiln. 

 The temperature of the kiln varies from about 300° F. in the case 

 of vitreous bond to 150° F. when the least refractory bonds are 

 used. 



A bond composed of sodium silicate and zinc oxid is used by 

 the Standard Emery Wheel Co. of Easton Pa., which till 1903 

 was located in Albany N. Y. This bond set at a very low tem- 

 perature, no fusion being required. 



On removal from the kiln, the wheels are trued and shaped in 

 a lathe, the cutting of the wheel being accomplished by the use 

 of black diamond (carbonado). 



Much of the success of an emery wheel depends on the selec- 

 tion of a bond suitable to the work to be accomplished. It is 

 therefore the present practice, when ordering emery wheels, to 

 specify the work which is to be accomplished by the wheel, 



^The above description is condensed from an article by C. N. Jenks on 

 corundum. Min. Ind. 1896. 5:26. 



