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CNC Technology

RADIUS AND FORM DRESSING

Contours, radii, and other special shapes can be ground by forming the reverse geometry on the grinding wheel. Various methods are used for this. Using a radius dresser that swings the single-point diamond in a preset arc is one method. The wheel dressing pantograph (Figure L-59) can form dress a vitrified grinding wheel to almost …

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TRUING AND DRESSING

When a new wheel is installed on the grinder, it must be trued before use. The cutting surface of a new wheel will run out slightly due to the clearance between the wheel bore and machine spindle (Figure L-51). Truing a wheel will bring every point on its cutting surface concentric with the machine spindle. …

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OTHER FACTORS IN WHEEL SELECTION

Grinding is probably the most challenging part of machine tool operation because so many variables must be integrated to get first-class results. Four of these factors relate to workpiece materials, which are constantly being changed in the shop environment. Four other factors in wheel selection are relatively fixed. Variable Factors Composition of the Workpiece For most steels …

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OTHER MARKING SYSTEMS

Because superabrasive usage is proportionally larger in Europe and Japan, wheels with markings other than Standard U.S. designations may be found. One example is the FEPA (Federation of European Producers of Abrasive Products) Standards. These standards apply to a variety of

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STANDARD WHEEL MARKING SYSTEMS

A standard wheel marking system (Figure L-47) is used for the purpose of identifying five major factors in grinding wheel selection: 1. Type of abrasive 2. Grit size A 60-J8V indicates the following: Selection of grit depends on the amount of stock to be removed and the surface finish requirements. Usually, coarse grits are used …

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SIZE AND SHAPE OF WHEELS

The standard coding system uses numbers 1 to 28 to indicate wheel size and shape. You should be familiar with five of the most common types: Type 1 Straight wheel (Figure L-42) Type 2 Cylinder wheel (Figure L-43) Type 6 Straight-cup wheel (Figure L-44) Type 11 Flaring-cup wheel (Figure L-45) Type 12 …

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CONCENTRATION

Concentration is a term applied to superabrasive grinding wheels that refers to the amount of abrasive contained in a unit volume of usable grinding wheel. A concentration of 100 corresponds to 72 carats in a cubic inch of wheel in the effective superabrasive volume of the grinding wheel. The concentration values are usually between 30 and 175. …

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CVSG

A recent development by the Norton Company has combined ceramic aluminum oxide (seeded gel abrasives) with cubic boron nitride (CBN). The grinding performance is three to five times that of conventional abrasives. This places the performance between conventional and superabrasives such as diamond or straight CBN. These new abrasives can be run on conventional grinding machines with sufficient power and rigidity to handle …

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TYPES OF ABRASIVES

Fused Aluminum Oxide Fused aluminum oxide is the most widely used abrasive in manufacturing. The higher the level of purity, the more friable (less tough) the grit becomes. The purer grades are often white in color and are used mainly on hardened steels. The grinding of hard steel causes a fairly rapid breakdown …

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GRINDING MACHINE SAFETY

Wheel Speed and Wheel Guards SAFETY FIRST The same general rules of safety apply to grinding machines as apply to other machine tools, but there are additional hazards because of the typically high speed of grinding wheels, which can store a great deal of energy. If a grinding wheel becomes cracked, it can fly …

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