::. FOR REFERENCE

MACHINE ACCESSORIES FOR SMOOTH GRINDING

Smooth finishing in industrial production has been at all times determined by severe requirements of surface quality, dimensions accuracy, parts shaping and positioning and processing of cutting-resistant materials. Material removing during grinding is characterized by low cut cross-section or cut thickness accordingly, simultaneous contacts of numerous cutting edges of an abrasive wheel with the workpiece, and by very high cutting speeds as compared to other processing methods.

Here are major types of polishing machines:

-circular grinding center-type machines
-circular grinding centerless machines
-internal grinding machines
-horizontal spindle surface grinding machines
-vertical spindle surface grinding machines
-longitudinal grinding machines
-circular continuous grinding machines
-thread-grinding machines
-coordinate grinding machines (jig grinders)
-abrasive metal-cutting machines
-all-purpose toll grinding machines

Machine accessories used for grinding must meet high quality requirements.

If possible, parts should be secured between non-rotational centers for circular exterior grinding. This will provide high grinding accuracy. To compensate lengthwise stretching, which may occur due to heating while grinding, tailstock center must be spring-controlled. Long thin parts must bear on back-rest units. Parts with processed apertures and having exterior cylindrical surfaces to be processed, are secured by mandrels. Common conic mandrels, motorized, hydraulic or pneumatic mandrels are used for compensation of inner diameter deviations. Heavy workpieces that require long-term grinding are secured in back-rest units, since center-type clamping can cause centering failures.
Collet holders and common three- or four-cam chucks with radially adjustable cams are used for circular interior grinding. Thin-walled bushings can be secured in expandable chucks.

To secure parts for flat-type grinding, magnetic chucks are often used, unless it is forbidden by workpiece shape and material. There are magnetic chucks of two types: permanent magnet and electromagnetic chucks. Parts that do not allow installation by means of magnetic chucks, in large-scale manufacturing are secured in special mechanically, pneumatically or hydraulically driven clamp mechanisms that match workpiece shape. In single-job or small-batch production following high accuracy machine accessories are used for flat-type grinding: turning and non-rotational precision vice, sine vice for grinding of precise angled surfaces, and sine one- and two-axis tables. Besides, there are dividing mechanisms with exchangeable dividing plates and exchangeable round tables for grinding ring-shaped parts.

When centerless grinding is performed, the workpiece is rotated between the grinding and the control wheels and is installed onto a workrest blade.

Grinding machines are equipped with wheel dressing mechanisms, which allow to shape worn-out grinding wheels. Diamond grit, dressing diamonds and rods, steel and diamond shaping rollers are used as dressing tools. There are also independent devices for dressing and balancing of grinding wheels.