GB556668A - Improvements in and relating to diamond tools for dressing, abrasive, polishing or like work, and to the manufacture thereof - Google Patents

Abstract

556,668. Ball mills; grinding surfaces. JEARUM, F. C. April 7, 1942, No. 4550. [Class 59] [Also in Groups XXIII and V] Crushing rollers or discs are formed by impregnating hard metallic particles with diamond particles or dust by pressure or impact and mounting or embodying such particles in a malleable metal or alloy or a plastic material by moulding under pressure with or without heat. The impregnation may be effected in a ball mill either hard tungsten or tungsten carbide balls being used or the balls being replaced by diamond masses of from 2 to 3 carats weight with or without a proportion of loose diamond dust, a suitable proportion being 30 parts diamond masses to 60 parts tungsten or tungsten carbide particles. After treatment, the diamond-impregnated particles are separated from the diamond masses and mixed with about 30 per cent. of a powdered malleable or bonding metal such as silver, a mixture of silver and iron, or the metal sold under the Registered Trade Mark "Invar." The mixture is then inserted into suitably shaped moulds or dies, preferably of molybdenum or chrome molybdenum, and subjected to a pressure of the order of 100 tons per square inch. Alternatively, the hard metallic particles, the diamond masses, and a soft malleable metal in powdered form may be introduced together into the ball mill and the diamond impregnated material so obtained may be moulded under pressure. The moulding operation may be carried out under heat, a suitable bond which will flux below 700‹C. being chosen so as not to harm the diamond particles. Instead of tungsten the hard metallic particles may be of molybdenum, molybdenum carbide, chromium, cobalt. titanium carbide, nickel-cobalt alloy or any hard steel alloy and the bonding material may be copper, copper and iron, copper and silver or other metal or alloy capable of flowing under pressure.