THREAD CUTTING AND EXPANSION COLLET Russian patent published in 2014 - IPC B23G1/02 

FIELD: process engineering.

SUBSTANCE: invention relates to thread cutting at lathes in hollow thin-wall cylinders, for example, rocket engine body. Preliminary boring of inner surface is performed by rough and finish passes followed by thread cutting in rocket engine body. After rough boring, rocker engine body sizes are thermally stabilised at normal temperature for at least 24 hours. Then, said body is clamped at lathe chuck with turn through 120 degrees to perform finish boring and thread cutting. Prior to clamping said body in said chuck, an expansion collet is fitted inside said body. Said expansion collet is composed by split bowl with cone there inside and lugs bent off outward. Said lugs form surface conical section conjugated with cone surface at back of said lug. They have contact sites made at the ends to form opposite force in rocket body compression zone. Note here that a through hole is made at cone centre to receive the screw to be screwed in bank threaded bore made at bowl leg. Bowl leg base has circular skew for connection with rocket engine body bottom.

EFFECT: minimised errors in cross-section shape.

2 cl, 4 dwg