Flare manufacturing method

摘要

It is an object of the present invention to reduce variations in dimensional accuracy such as the outer-diameter accuracy and roundness of a flare shape and the concentricity between the bulb portion and the flare portion. According to the present invention, a lower mold (1) formed of a metallic material and forming a recess flare shape (1a) that is subjected to surface treatment forms a flare shape (21b) almost identical to the flare shape (1a) by means of the rotational motion of a rotating head portion (2). An upper mold (10) is fitted in the lower mold (1) to form a flare-shaped gap portion (13), into which glass is forced to form a flare shape (22).