Grinding is the process of removing metal by the application of abrasives which are bonded to form a rotating wheel. When the moving abrasive particles contact the workpiece, they act as tiny cutting tools, each particle cutting a tiny chip from the workpiece. It is a common error to believe that grinding
abrasive wheels remove material by a rubbing action; actually, the process is as much a cutting action as drilling, milling, and lathe turning.
The grinding machine supports and rotates the grinding
abrasive wheel and often supports and positions the workpiece in proper relation to the wheel.
The grinding machine is used for roughing and finishing flat, cylindrical, and conical surfaces; finishing internal cylinders or bores; forming and sharpening cutting tools; snagging or
removing rough projections from castings and stampings; and
cleaning, polishing, and buffing surfaces. Once strictly a
finishing machine, modem production grinding machines are
used for complete roughing and finishing of certain classes of work.
GRINDING MACHINE SAFETY
Grinding machines are used daily in a machine shop. To
avoid injuries follow the safety precautions listed below.
Wear goggles for all grinding machine operations.
Check grinding wheels for cracks (Ring Test Figure 5-11)
Never operate grinding wheels at speeds in excess of the
Never adjust the workpiece or work mounting devices
when the machine is operating
Do not exceed recommended depth of cut for the grinding
wheel or machine.
Remove workpiece from grinding wheel before turning
Use proper wheel guards on all grinding machines.
On bench grinders, adjust tool rest 1/16 to 1/8 inch from the wheel.
TYPES OF GRINDING MACHINE
From the simplest grinding machine to the most complex,
grinding machines can be classified as utility grinding
machines, cylindrical grinding machines. and surface
grinding machines. The average machinist will be concerned
mostly with floor-mounted and bench-mounted utility
grinding machines, bufting machines. and reciprocating
surface grinding machines.
UTILITY GRINDING MACHINES
The utility grinding machine is intended for offhand
grinding where the workpiece is supported in the hand and
brought to bear against the rotating grinding abrasive wheel. The accuracy of this type of grinding machine depends on the operator’s dexterity. skill, and knowledge of the machine’s capabilities and the nature of the work. The utility grinding machine consists of a horizontally mounted motor with a
grinding abrasive wheel attached to each end of the motor
The electric-motor-driven machine is simple and
common. It may be bench-mounted or floor-mounted.
Generally, the condition and design of the shaft bearings as well as the motor rating determine the wheel size capacity of the machine. Suitable wheel guards and tool rests are
provided for safety and ease of operation. Grinding machines come in various sizes and shapes as listed below.
Floor Mounted Utility Grinding Machine
The typical floor-mounted utility grinding machine stands
waist-high and is secured to the floor by bolts. The floormounted utility grinding machine shown in Figure 5-1 mounts two 12-inch-diameter by 2-inch-wide grinding
abrasive wheels. The two wheel arrangement permits
installing a coarse grain wheel for roughing purposes on one end of the shaft and a fine grain wheel for finishing purposes on the other end this saves the time that would be otherwise consumed in changing wheels.
Each grinding abrasive wheel is covered by a wheel guard
to increase the safety of the machine. Transparent eyeshields. spark arresters. and adjustable tool rests are provided for each grinding wheel. A tool tray and a water pan are mounted on
the side of the base or pedestal. The water pan is used for
quenching carbon steel cutting took as they are being ground. Using the 12-inch...