4. In the traverse surface grinding of a steel workpiece, 3 inch by 6 inch by 9 inch large, as shown in the following figure, the 90 grit aluminum oxide grinding wheel has a diameter of 6 inches. The cross feed (f) used is 1/4 inch, the radial depth of engagement is 1/16 inch, the spindle speed is 3,500 rpm, and the traverse speed is 1 in/s. In this case the grain aspect ratio is 4 (1) Determine the total time needed to grind one flat surface. (2) In order to cut down the grinding time by 50%, it has been suggested that either Option 1. the cross feed should be doubled, or Option 2. the traverse speed should be doubled. If the same grinding wheel is to be used while any of the above suggestions is followed, what is the effect of each option on the change of wheel hardness grade in grinding? The wheel hardness grade in grinding is determined by the maximum uncut chip thickness, acmarc- The increase in ac, max tends to make wheel behave softer amax 4v Crv When using the equation. , in Chap. 4 to calculate de,max, please note that the f in this equation is for plunge grinding. This is the transverse grinding configuration. radial depth of engagement f ap traverse velocity cross feed 9"- 6"