GRINDING MACHINES - Carnegie Mellon University

1 TC 9-524 Chapter 5 GRINDING MACHINESG rinding is the process of removing metal by the applicationof abrasives which are bonded to form a rotating wheel. Whenthe moving abrasive particles contact the workpiece, they actas tiny cutting tools, each particle cutting a tiny chip from theworkpiece. It is a common error to believe that grindingabrasive wheels remove material by a rubbing action; actually,the process is as much a cutting action as drilling, milling, andlathe GRINDING machine supports and rotates the grindingabrasive wheel and often supports and positions the workpiecein proper relation to the GRINDING machine is used for roughing and finishing flat,cylindrical, and conical surfaces; finishing internal cylindersor bores; forming and sharpening cutting tools.

2 Snagging orremoving rough projections from castings and stampings; andcleaning, polishing, and buffing surfaces. Once strictly afinishing machine, modem production GRINDING MACHINES areused for complete roughing and finishing of certain classes MACHINES have some special safety precautionsthat must be observed. These are in addition to those safetyprecautions described in Chapter PRECAUTIONSGRINDING MACHINE SAFETYG rinding MACHINES are used daily in a machine shop. Toavoid injuries follow the safety precautions listed goggles for all GRINDING machine GRINDING wheels for cracks (Ring Test Figure 5-11)

3 Before operate GRINDING wheels at speeds in excess of therecommended adjust the workpiece or work mounting deviceswhen the machine is operatingDo not exceed recommended depth of cut for the grindingwheel or workpiece from GRINDING wheel before turningmachine proper wheel guards on all GRINDING bench grinders, adjust tool rest 1/16 to 1/8 inch fromthe 9-524 TYPES OF GRINDING MACHINESFrom the simplest GRINDING machine to the most complex, GRINDING MACHINES can be classified as utility grindingmachines, cylindrical GRINDING MACHINES .

4 And surfacegrinding MACHINES . The average machinist will be concernedmostly with floor-mounted and bench-mounted utilitygrinding MACHINES , bufting MACHINES . and reciprocatingsurface GRINDING GRINDING MACHINESThe utility GRINDING machine is intended for offhandgrinding where the workpiece is supported in the hand andbrought to bear against the rotating GRINDING abrasive accuracy of this type of GRINDING machine depends on theoperator s dexterity. skill, and knowledge of the machine scapabilities and the nature of the work.

5 The utility grindingmachine consists of a horizontally mounted motor with agrinding abrasive wheel attached to each end of the electric- motor -driven machine is simple andcommon. It may be bench-mounted or , the condition and design of the shaft bearings aswell as the motor rating determine the wheel size capacity ofthe machine. Suitable wheel guards and tool rests areprovided for safety and ease of operation. GRINDING machinescome in various sizes and shapes as listed Mounted Utility GRINDING MachineThe typical floor-mounted utility GRINDING machine standswaist-high and is secured to the floor by bolts.

6 The floor-mounted utility GRINDING machine shown in Figure 5-1mounts two 12-inch-diameter by 2-inch-wide grindingabrasive wheels. The two wheel arrangement permitsinstalling a coarse grain wheel for roughing purposes on oneend of the shaft and a fine grain wheel for finishing purposeson the other end this saves the time that would be otherwiseconsumed in changing GRINDING abrasive wheel is covered by a wheel guardto increase the safety of the machine. Transparent arresters. and adjustable tool rests are provided for eachgrinding wheel.

7 A tool tray and a water pan are mounted onthe side of the base or pedestal. The water pan is used forquenching carbon steel cutting took as they are being the 12-inch wheel, the machine provides a maximumcutting speed of approximately SFPM. The 2-HPelectric motor driving this machine has a maximum speed Type Utility GRINDING MachineLike the floor mounted utility GRINDING machine, one coarsegrinding wheel and one fine GRINDING wheel are usuallymounted on the machine for convenience of operation.

8 Eachwheel is provided with an adjustable table tool rest and an eyeshield for protection. On this machine, the motor is equippedwith a thermal over-load switch to stop the motor if excessivewheel pressure is applied thus preventing the burning out ofthe motor . The motor revolve at RPM maximum toprovide a maximum cutting speed for the 7 inch grindingwheels of about 6,300 surface feet per minute (SFPM).TC 9-524 Bench-Type Utility Drill GRINDING MachineThe bench-type drill GRINDING machine is intended for drillsharpening.

9 The accuracy of this type of grinder is notdependent on the dexterity and skill of the operator becausethe drill is placed in a holding device. The holding deviceplaces the drill in the correct position for the clearance andincluded angle. For more information on this machine refer tochapter Utility GRINDING and BuffingMachineThe bench-type utility GRINDING and buffing machine is moresuitable for miscellaneous GRINDING , cleaning, and buffing It isnot recommended for tool GRINDING since it contains no toolrests, eyeshields, or wheel guards.

10 This machine normallymounts a 4 inch-diameter wire wheel on one end. The wirewheel is used for cleaning and the abrasive wheel is used forgeneral GRINDING . One of the two wheels can be removed and abuffing wheel mounted in its place for buffing and 1/4-HP electric motor revolves at a maximum of 3,450 RPM. The maximum cutting speed of the 4-inch-diameterwheel is approximately 3,600 Tool and Cutter GrinderThe bench-type tool and cutter grinder, see Figure 5-4, wasdesigned primarily to grind end mills.