Reinsertable adjustable boring bar

An adjustable boring bar combination comprising:

• (a) an elongate bar having an axis of rotation and a first recess in the working end of said bar extending transversely to said axis across said bar with parallel side walls lying in planes parallel to said axis of rotation, and a second transverse recess formed as a well in the bottom of said first recess and closed at each end,
• (b) an adjustment screw having a threaded shank with each end mounted for rotation in said bar at the respective ends of said second recess and axially retained in said bar,
• (c) an index block slidably positioned in said well and having a projection extending into said first recess and having a tapped hole to receive said threaded shank of said adjustment screw,
• (d) a boring head having a rib with parallel side walls to fit slidably in said first recess and a hole on said rib to receive said projection on said index block, and
• (e) means to retain said rib in said first recess comprising a lock pin in a transverse hole aligned with said first recess and communicating therewith through an opening in a wall of said first recess, and a pressure screw to move said pin laterally against one side of said rib of said boring head.