51) What is the angle between the adjustable jaws of a three jaw chuck?

52) Which part of screw rod of 4 jaw chuck permits the screws to rotate but not to advance?

53) Which part of the lathe is H shaped cast iron on the bed ways?

54) Which part of carriage is only for possible manual operation?

55) Which part of lathe slides over the bedways between headstock and the tailstock?