APPARATUS FOR MAKING GLASS ROD

PURPOSE:To inexpensively and easily obtain a glass rod for welding of high roundness, which is used as a welding material for producing ferrite magnetic heads, by charging and melting glass materials in a crucible having the large-diameter part and the small- diameter part, making the materials semifused in the small-diameter part using a low-temperature subheater, extruding the semifused materials and conveying with rollers. CONSTITUTION:Glass melt 14 is charged in a heat-resistant metal crucible 20 which is composed of the cylindrical part of a large diameter 21 having a opening part, the cylindrical part of a small diameter 22 and the funnel part 23 connecting the large diameter part 21 to the small diameter part 22. The glass melt is kept in the liquid state by heating with furnace 24 around the large-diameter cylinder 21, then made semifused in the small-diameter part 22 by lowering temperature with the preform-forming furnace 25 and allowed to go down through the small-diameter part 22, then an exact cylindrical glass 14 is allowed to flow out from the end of opening part and to be drawn out with rollers 26, as the viscosity is controlled with the elec tronic controller 27 and a couple of rollers 26 are controlled in their rotation whereby the glass 11 of exact roundness is obtained, as the drawing ratio and the diameter are adjusted.