Document zzawke79xjOYp9BOXQEXev37m

BENCH AND STAND GRINDERS DRESSING 1 Wear a face shield over your goggles for pro tection against heavy particles 2 Use a dressing tool approved for the job Never use a lathe cutting tool 3 Inspect star dressers for loose shaft and worn disks 4 Round off the wheel edges with a hand stone before and after dressing to prevent the edges from chipping 5 Use the work rest to support and guide the tool Use a tool holder if one is available 6 Apply moderate pressure slowly and evenly 7 Always apply diamond dressers at the center or slightly below the center, never above Fig 26-24 --Major safety measures to be taken in a wheel dressing operation wheel may overheat at the nm and crack Operators, therefore, should be trained and supervised to make sure they clamp work tightly, always turn a magnetic chuck on before applying the wheel, and control the speed and depth of the work Baffle plates on each end of a surface gnnder are generally standard equipment, but should include some provision for ex hausting the grinding dust (Fig 26-25) Internal grinders can be guarded with an automatic positioning hood that covers the grinding wheel when it is m the retracted or idling position Grindstones Grindstones are made from natural sand stone, usually the Ohio and the Huron types Huron grindstones are harder, have a finer grain, and can be operated at higher speeds than the Ohio Ohio grindstones should never be run at a peripheral speed greater than 3000 sfpm, and for ordinary purposes not over 2500 sfpm Huron stones may be safely run at 3000 sfpm, but should not exceed 3500 sfpm Stones of unknown composition should never be run more than 2500 sfpm and ordi narily not more than 2000 sfpm The size and weight of grindstones require a stand that is rigidly constructed and heavy enough to hold the stone securely mounted on a solid foundation to withstand vibration Since gnndstones are run wet, all possible precautions should be taken to prevent slipping accidents near the stones Rough concrete or other nonskid floor material is recommended Gnndstones should be carefully inspected for cracks and other defects as soon as they are received from the manufacturer Those not to be used at once should be stored m a dry, uniformly heated room In storage they should be placed so that they will not be damaged Many gnndstone failures result from faulty handling and from incorrect methods used in mounting Gnndstones should not be left partially submerged in water This practice causes an unbalanced stone that may break when rotated Wooden wedges should not be used on power-dnven stones Often such wedges are dnven excessively tight or be come wet and swell In either case, cracks start m the comers of a square center hole, radiate outward, and so weaken the stone that ruptures occur at norma) speed After the stone has been centered, the cen- FlC 26-25 --Guarding and exhaust provisions for a surface gnnding operation 779