| 摘要 |
PURPOSE:To obtain easily and continuously an internally worked pipe having a small wall thickness by connecting a grooved plug for internal working to a floating plug and maintaining the position thereof. CONSTITUTION:When a head 3 is rotated at a high speed in a specified direction while a pipe 1 is moved, the pipe 1 is reduced by rolls 32 rotating like a planet and is pressed onto a grooved plug 34, by which prescribed grooves or projections 12 are formed on the inside surface of the pipe 1. Advancing force acts on the plug 34 according to the friction with the inside surface of the pipe in this stage but the plug 34 is supported by a plug 21 via a connecting bar 5 and is therefore held exactly at all times at a position adequate with respect to the rolls 32. The internally worked pipe is drawn in succession through the 2nd die 4 and therefore the resulting worked surface 11 has a smooth outside surface and an exact outside diameter. |
