This piece started out as a 550 lb.(249.48 kg) blank. At this point it weighs 163 lbs. (73.94 kg) The pilot or the part of the piece standing proud on the top as the part is sitting now, has to be accurate to +/- .0005" That is a total allowance of one thousandth of an inch. The operation being performed in this picture is the starting process of drilling a hole that will be tapped to accommodate a lifting eye.