PURPOSE: To perform the inner face grooving with good accuracy by passing a blank pipe through the space with the grooved plug being provided freely rotatably with rotating a taper roll and work member so that the rotation direction thereof becomes in the reverse direction each other for the pipe axis.
CONSTITUTION: The rotary taper roll 1 in ≥three pieces having a taper face 1' is provided freely rotatably for the pipe axis of a blank pipe W and the floating plug 2 having an approach face 2' is arranged among the taper rolls 1. At the front of the taper roll 1, the rotary work member 5 equipped a planetary ball or roll 6 is provided and the freely rotatable groove plug 3 linked to the plug 2 is arranged at the position of the work member 5. In case of working the inner face groove 7 on the blank pipe W, the pipe W is passed with rotating the taper roll 1 and work member 5 so that the rotary direction thereof becomes in the reverse direction each other for the pipe axis. In this way a deep inner face groove or the inner face groove of a thin pipe can be worked with good accuracy.
SATO TAKUYUKI
ISOZAKI AKIO
