Wheel Traverse

This is taken as the distance the abrasive wheel travels axially during a complete revolution of the work. While experts differ as to what proportion of the face of the wheel this should be, it would appear that where operating conditions will stand it, a traverse of above one-half the wheel face width per work revolution is desirable when rough grinding work. Fig. 326 shows the traverse markings upon a piece of ground work.

Grinding Allowances

When in grinding practice the work has been previously rough turned, it is customary to leave an amount of stock to be removed in the grinding machine dependent upon the size and character of the work and upon the roughing out method employed.

Table XII gives allowances left for grinding as worked out by the Landis Tool Company. If the roughing out is done, using an exceptionally coarse feed, as shown in Fig. 327, the tabulated allowances will need to be exceeded. It is well to note here that tabulated grinding details in machine construction are useful chiefly as a starting basis.

Fig. 327. Roughing-Out for Grinding Showing Heavy Cut.

Abrasive Wheels

Large enterprises are devoted to the production of artificial abrasives. Increased knowledge in the manufacture of the wheels themselves and an added knowledge in wheel selection has materially changed the abrasive wheel industry from that of previous years. The greater portion of modern machine grinding is now done with the manufactured abrasives. These are in most part very efficient in cutting qualities and are sold under a variety of trade names such as alundum, aloxite, carborundum,

Table XII. Allowances For Grinding

crystolon, and several others. Abrasive wheels can be had also in a variety of degrees of" hardness, coarseness, and varying bonds, as is seen by consulting Tables XIII and XIV. Degrees of hardness, coarseness, and bonding condition make up what is known as the "grain" and the "grade" of the abrasive wheel.