If the proper authority be given the metallurgical engineer to govern the handling of the steel from the time it is purchased until it is assembled into finished product, mild-analysis steels can be used and the quality of the finished product guaranteed. It was only through the careful adherence to these fundamental principles that it was possible to produce 20,000 Liberty engines, which are considered to be the most highly stressed mechanism ever produced, without the failure of a single engine from defective material or heat treatment. MAKING STEEL BALLS Steel balls are made from rods or coils according to size, stock less than 9/16-in. comes in coils. Stock 5/8-in. and larger comes in rods. Ball stock is designated in thousandths so that 5/8-in. rods are known as 0.625-in. stock. Steel for making balls of average size is made up of: Carbon 0.95 to 1.05 per cent Silicon 0.20 to 0.35 per cent Manganese 0.30 to 0.45 per cent Chromium 0.35 to 0.45 per cent Sulphur and phosphorus not to exceed 0.025 per cent For the larger sizes a typical analysis is: Carbon 1.02 per cent Silicon 0.21 per cent Manganese 0.40 per cent Chromium 0.65 per cent Sulphur 0.026 per cent Phosphorus 0.014 per cent Balls 5/8 in. and below are formed cold on upsetting or heading machines, the stock use is as follows: TABLE 14.--SIZES OF STOCK FOR FORMING BALLS ON HEADER ------------------------------------------------------- Diameter of | Diameter of | Diameter of | Diameter of ball, inch | stock inch | ball, inch | stock, inch -------------|-------------|-------------|------------- 1/8 | 0.100 | 5/16 | 0.235 5/32 | 0.120 | 3/8 | 0.275 3/16 | 0.145 | 7/16 | 0.320 7/32 | 0.170 | 1/2 | 0.365 1/4 | 0.190 | 9/16 | 0.395 9/32 | 0.220 | 5/8 | 0.440 ------------------------------------------------------- For larger balls the blanks are hot-forged from straight bars. They are usually forged in multiples of four under a spring hammer and then separated by a suitable punching or shearing die in a press adjoining the hammer. The dimensions are: ----------------------------------------------------------- Diameter of ball, | Diameter of die, | Diameter of stock, inch | inch | inch -------------------|------------------|-------------------- 3/4 | 0.775 | 0.625 7/8 | 0.905 | 0.729 1 | 1.035 | 0.823 -----------------------------------------------------------