Cutting test was carried out by using oxygen of various purities,i.e. 99.8 to 85 per cent. From the test results the relationships among oxygen purity, the maximum thickness that can be cut and cutting variables were obtained with a fair degree of accuracy. The main feature of the deleterious effects of lower purity oxygen is that for a cut of given thickness cutting speed must be lowered, and tip size enlarged. Consequently, the lower the purity of oxygen, the lower the cutting efficiency. The

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... purity of commercially pure oxygen is 99.8 per cen. If this purity is raised to absolute 100 per cent, a conside-