furnace preheated to 2420 u00b0 f to 2460 u00b0 f and removed from the furnace when the o d of the cylinder reaches about 2410 u00b0 f the cylinder is then rapidly transferred to a centrifugal spinner and spun at a speed sufficient to generate a 75 g force on the i d of the cylinder the spinning continues until the o d of the cylinder reaches a temperature of about 1600 u00b0 f the cylinder is slow cooled to room temperature over a period of two days by placing it in a cooling pit and covering it with with an insulating material such as vermiculite following cooling the cylinder is rough bored to an internal dimension from 0 012 34 to 0 025 34 less than the desired finish dimension the cylinder is then heat treated it is placed in a furnace pre heated to about 1900 u00b0 to 2150 u00b0 f and allowed to reach an o d temperature as measured by an optical pyrometer of about 1900 u00b0 f and held at that temperature for about 45 minutes the cylinder is then rapidly transferred to a spinner and spun until the o d temperature reaches about 600 u00b0 f during the cooling cycle on the spinner both water and forced air are used to obtain the desired cooling rate during the treatment cycle with a typical total cooling time being about 5 minutes when the o d reaches about 600 u00b0 f it is removed from the spinner and cool slowly to ambient temperature the cylinder is.