EXTENSION-TYPE REAMER BIT Russian patent published in 2011 - IPC E21B7/28 

FIELD: oil and gas industry.

SUBSTANCE: extension-type reamer bit includes centraliser, housing with central through channel and slots, blades equipped with rock-destructing elements and projections in the form of teeth, which are fixed in slots of housing with possibility of being extended, and extension mechanism of blades to working position, which includes hollow shaft with piston, and pusher. Hollow shaft is installed so that it is fixed against being rotated relative to housing. Reamer bit has blade locking device in non-working position, which includes radially spring-loaded annular segments interacting with pusher and located in shaft groove, and groove mating those segments and made in inner wall of housing. Dies of centraliser are extension-type and installed in additional slots of housing. Shanks of dies are equipped with projection of dovetail type, which interact with mating slots made on inclined surfaces of fixing device fixed on shaft below piston and above sleeve.

EFFECT: reliable and long-life design, extended life of reamer bit equipment, and strictly required diameter of gauged well shaft throughout the length of extended interval.

4 cl, 5 dwg