Yinglong Superhard Materials Manufactory
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YingLong Superhard Materials Manufactory

Add: Lintong District, Xi'an, China

Tel: +86-29-63354776/63354775

Fax: +86-29-63354775/83852230

Skype: HeroHome-Sunny

Email: Info@HeroHomecn.com



What is Grinding?

What is Grinding? 

    Center less grinding. Center less grinding involves passing a cylindrical work piece, which is supported by a rest blade, between two wheels, i.e., the grinding wheel and the regulating or feed wheel.

The grinding wheel does the actual grinding, while the regulating wheel is responsible for rotating the work piece as well as generating the longitudinal feed. This is possible because of the frictional characteristics of that wheel, which is usually made of rubber-bonded abrasive.

The axis of the regulating wheel is tilted at a slight angle with the axis of the grinding wheel. Consequently, the peripheral velocity of the regulating wheel can be resolved into two components, namely, work piece rotational speed and longitudinal feed.

These can be given by the following  equations:

          V work pieceV regulating wheel×cosα

          Axial feedV regulating wheel×c×sinα

    Where c is a constant coefficient to account for the slip between the work piece and the regulating wheel (c=0.94~0.98).

    The velocity of the regulating wheel is controllable and is used to achieve any desired rotational speed of the work piece. The angle α is usually taken from 1°to 5°and the larger the angle, the larger the longitudinal feed would be.

    When α is taken as 0°, i.e., the two axes of the grinding and regulating wheels are parallel, there is no longitudinal feed of the work piece.

Grinding Wheels

    Grinding wheels are composed of abrasive grains having similar size and a binder. The actual grinding process is performed by the abrasive grains. Pores between the grains within the binder enable the grains to act as separate single-point cutting tools.

    These pores also provide space for the generated chips, thus preventing the wheel from clogging. In addition, pores assist the easy flow of coolants to enable efficient and prompt removal of the heat generated during the grinding process.

    Grinding wheels are identified based on their shape and size, kind of abrasive, grain size, binder, grade (hardness), and structure.

    Shape and size of grinding wheels. Grinding wheels differ in shape and size, depending upon the purpose for which they are to be used. Include the following types

1)Straight wheels used for surface, cylindrical, internal, and center less grinding.

2)Beveled-face or tapered wheels used for grinding threads, gear teeth, and the like.

3)Straight recessed wheels for cylindrical grinding and facing.

4)Abrasive disks for cutoff and slotting operations. (thickness 0.02 up to 0.2in. (0.5 to 5mm)).

5)Cylinders, straight cups, and flaring cups are used for surface grinding with the end face of the wheel.

    The main dimensions of a grinding wheel are the outside diameter D, the bore diameter d, and the height H. These dimensions vary widely, depending upon the grinding process for which the wheel is to be used.

    Kind of abrasive. Grinding wheels can be made of natural abrasives such as quartz, emery, and corundum or of industrially prepared chemical compounds such as aluminum oxide or silicon carbide (known as carborundum).

    Generally, silicon carbide grinding wheels are used when grinding low-tensile-strength materials like cast iron, whereas aluminum oxide wheels are employed for grinding high-strength metals such as alloy steel, hardened steel, and the like.

   Grain size of abrasive used. As you may expect, the grain size of the abrasive particles of the wheel plays a fundamental role in determining the quality of ground surface obtained.

    The finer the grains, the smoother the ground surface is. Therefore, coarse-grained grinding wheels are used for roughing operations, whereas fine-grained wheels are employed in final finishing operations.

The grade of the bond. The grade of the bond is actually an indication of the resistance of the bond to pulling off the abrasive grains from the grinding wheel. Generally, wheels having hard grades are used for grinding soft materials and vice versa.

    If a hard-grade wheel were to be used for grinding a hard material, the dull grains would not be pulled off from the bond quickly enough, thus impeding the self-dressing process of the surface of the wheel and finally resulting in clogging of the wheel and burns on the ground surface.

    In fact, the cutting properties of all grinding wheels must be restored periodically by dressing with a cemented carbide roller or a diamond tool to give the wheel the exact desired shape and remove all worn abrasive grains.

    Structure. Structure refers to the amount of void space between the abrasive grains. When grinding softer metals, larger void space are needed to facilitate the flow of the removed chips.

    The binder. Abrasive particles are bonded together in many different ways. These include bond, silicate, rubber, retinoid, shellac, and ox chloride. Nevertheless, the bond is the most commonly used one.

    In fact, the standard marking system is employed for distinguishing grinding wheels, by providing all the preceding parameters in a specific sequence.