Document k9eBXJMB5yD5QD1Vqjq9JmkDn

-46- Operation Particles per cu. ft. Dressing 1-l/Z" x~TZ" Aloxite Wheel (Grit 40.Grade H, Bond S3).................................. 226,660 (Evidently particles in the cloud of dust thrown off by the 2-1/2" x 6" Metcalf .Emery Wheel Dresser are larger than 30 microns in size) Grinding "Diamond Point" Chisel on 1-1/2" x 12" Aloxite Wheel (Grit 40, Grade H).2,067,360 ;Grinding 2-1/2" x 6" Landis die on 2-1/2" x l-l/2" x 12" Aloxite Wheel (Grit 4SA-P P678)...................................... ...................... 755,203 Under the Konlmeter microscope dust particles in samples taken while dressing the 1-1/2" x 12" Aloxite Wnee} appeared slightly angular with a yellowish tinge and were"five microns or less in size. About 75J? of the particles from grinding the Landis die were round, opaque, and less than 1 micron in sizej 25%e were slightly angular crystalline, less than 2 microns. "Particles from grinding the diamond point chisel were less quartz-like than those from grinding the die. This difference is, of course, due to difference in the composition of the two wheels. On an average, Landis tool grinders are used about twenty hours a week, usually by different men. G - YANKEE DRILL GRINDER: Used for grinding all types of drill bits. Has a side grinding type 1" x 1-1/2" x 9" Carborundum Aloxite (Grit 30, Grade M, Bond 28) Wheel. Operating speed 1735 RPM. On an average a Yankee Drill Grinder runs about three hours a day and is used by four different men with an average servioe of twelve years, Samples taken during the grinding of a 2-5/16" high speed drill had an ave rage _oI 1,000,829 "particles, ten microns or less, per cubic foot. About 70% of these dust particles are slightly crystalline in appearance, five microns or less1 in sizej SO% were rounded, semi-opaque, over ten microns in size. There were also a few small metallio shreds. No exhaust or dust colleotor is used in this grinding. E - AUTOMATIC CIRCULAR SAW SHARPENING MACHINE: There are a number of these grinders in use in the wood working operations - such as in the production of wooden barrels, boxes and crates - closely associated with the refining of petroleum pro ducts. Since they are automatic when once put in operation, there is very little dust hazard except where no exhaust or dust collectors have been installed and the dust produced is thrown into the filing room atmosphere. Automatic Circular Saw Sharpening Machines are equipped with l/4" x 8" Norton Alundum Wheels (Grain 60, Grade N), 3/B" x 8" Norton Alundum (1946 M) wheels, or l/2" x 6" Carborundum wheels. The average dust produoed during operation of these machines is: Wheel Particles per cu. ft. l/2" x 1/4" x 3/8" x l/4" x 6"Carborundum.................................................................................... 12" " 8"Alundum (1946M)............................................................................ 8" " (Grain60, Grade N)..................................................... 1,923,280 3,568,320 2,095,680 1,461,312 About 9B% of dust particles in samples taken while sharpening circular saws on the Carborundum wheels were black metallic in appearance, and one micron or less in size. About 75% of the particles from the Alundum wheels were rounded crystal line, 5 miorons or under in size, and 25% round black metallic, about one micron or less in size. There were a number of small metallio shreds in the samples from the thicker (3/8" x 8") wheel. I - AUTOMATIC BAND SAW GRINDER: After the Ban^ Saw has been inserted and the EM001536