| abstract |
A method of manufacturing a glass tube (6), comprising the step of controlling a stress added to the inner peripheral side or outer peripheral side of the glass tube (6) when the glass material (3) is heated by a heating element (41) disposed around the glass material (3) for softening the glass material and the glass material (3) is gradually formed into the glass tube (6) by relatively press-fitting a boring tool (31) in the softened area of the glass material (3), wherein the control of the stress can be performed, for example, by controlling an internal pressure or an external pressure on the glass tube (6), whereby the high quality glass tube (6) can be provided by preventing the glass tube (6) from being deformed immediately after boring, and such a problem with the glass tube (6) that a residual stress after cooling is non-uniformed and cracking tends to occur at the time of re-heating can be solved. |