Exemption availability for job work castings remains despite incidental scrap when used in manufacture of specified goods. Exemption under notification Nos. 83/94 and 84/94 applies where castings received from job-workers are used in the manufacture of specified final products; the principal manufacturer must undertake that such goods will be used in or in relation to manufacture of exempt goods or those falling under specified tariff headings and to pay excise duty if that undertaking is breached. Incidental generation of waste or scrap during manufacture does not negate the exemption, and the percentage of waste is irrelevant so long as the castings are used for the specified products.