An 8-in-diameter grinding wheel rotates at a surface speed of 4000 ft/min in a surface grinding job performed on a flat piece of 4340 steel with hardness = 325 BHN. There are 300 active grits/in2 of wheel surface, and the operation is performed dry. Infeed = 0.0015 in per pass, crossfeed (transverse feed) = 0.20 in, and the reciprocating speed of the work is 30 ft/min. Determine (a) length of contact between the wheel and the work, (b) volume rate of metal removed, (c) number of chips formed per unit time, and (d) average volume per chip? (e) If the tangential cutting force on the workpiece = 23 lb., what is the specific energy U calculated for this job?