by L. T. CHRISTOPHERSON
Several technical publications, within the last year, have dealt quite extensively with the treatment of ablasives, and have proven valuable to the people who are using grinding and polishing materials.
Presuming that there are some readers of this article who use these various abrasives just as they come from the supply house and find at times that these powders are not quite satisfactory will find a simple check test which will be of value.
Arkansas Oil Stone powder and pumice are used quite extensively in the reduction of balance pivots and pinions and inasmuch as it is not quite uniform in the granules-some dissatisfaction may occur.
In order to avoid such trouble use a steel slab and a stiff spatula ground off to about 3 inches long and at end of blade sharpen on a 45 degree at right angle to the blade, then place a small amount of the powder on steel block to which has been placed a small amount of oil, preferably liquid petrolatum, then rub the powder with quite a little pressure to a smooth paste, being sure that you use oil sparingly. This method is also used on other grinding powders, except diamond. When you have rubbed out powder so that it feels smooth, scrape it off the slab and place on your tin slip polishing block. This block should have several compartments, each one of which should contain a different abrasive. When you desire to grind some flat pieces the abrasive is always available and always of the right consistency, whether you desire to use crocus powder on pivot polisher, wig-wag, or tin slip.
Regarding diamond powder, do not I use this on the polishing block. Keep separate and use olive oil as a mix. In checking diamond powder, it is necessary to use a small crusher. I have one which is very adaptable for this abrasive. I use a round block of bard steel 2 inches high and It inches in diameter. In center I have a round depression 10 MM across the top edge. Be sure that the pestle fits closely. To check your diamond powder, place therein a small quantity with a little olive oil and use pestle in a grinding motion. Use a lot of pressure until mixture is smooth. Remove mixture, using a very small spatula, and place in a slim glass vial to which some gasoline has been added. Shake well and let stand about 24 hours and use the top settlings for fine polish. It is just right to use for removal of pits in end stones. I have a special diamond lapp used for that purpose. Should you wish to experiment on a formula of your own in the grinding of different materials, a small crusher of this kind is valuable. I might add that diamond abrasive is one of the most costly, yet it is inexpensive because so little of it is used. There is nothing that will take its place.