For turning cast iron the speed of the job past the tool may be 150in. to 190 in. per minute; for wrought iron, 260 in. to 280 in. per minute; for yellow brass, 300 in. per minute; and for chilled rolls, 3ft. per minute. In boring, the following speeds are recommended: - For cast iron, SO in. per minute, and for wrought iron, 140 in. per minute. For screw-cutting in steel a suitable speed is 7 1/2 ft. per minute; it, however, should depend on the nature of the material, Bessemer steel, for instance, being turned or screw-cut at a higher speed than cast steel. To deter-mine approximately the peripheral speed of the job in inches per minute, multiply its diameter in inches by 3 1/2, or by 3.1416, and by the revolutions per minute.