Fig. 2045.
Fig. 2046.
Fig. 2047.
The circumferential surface of a wheel may be employed to grind a flat surface, providing that the work be traversed to the wheel, as in the side view in [Fig. 2045]. In this case, however, the cut must be taken while the work p is travelling in the direction denoted by the arrow j, and no cutting must be done while the work is travelling back in the direction of k. After the work has traversed back in the direction of k, and is clear of the wheel, the cut is carried farther across the work by moving or feeding the work in the direction of the arrow in the front view, [Fig. 2046]. In this case the whole surface of the work passes beneath the wheel thickness, and the wheel face wears parallel to the wheel axis, producing a true plane (supposing the work to be moved in straight lines), save in so far as it may have been affected by the reduction of the diameter of the emery wheel from wear, which is not found sufficient to be of practical importance. If the whole surface of the work does not pass across or beneath the wheel thickness the wheel face may wear taper. Suppose, for example, that in [Fig. 2047], p is a piece of work requiring to have produced in it a groove whose bottom is to be parallel to the lower surface f. Then the upper work surface being taper the thick side a would wear away the side b of the wheel, and the groove ground would not be parallel to f.
