Oscillating cutting toolhead

In a boring tool, a combination comprising a toolhead having a longitudinal axis and being provided with a slot extending transverse to said axis;

• a pair of oppositely directed cutting knives floatably mounted in said slot and movable away from each other to a cutting position and toward each other to an inactive position, each of said cutting knives having an outer cutting edge and an inner end face opposite a corresponding end face of the other cutting knife;
• biasing means connected to said cutting knives for biasing the same toward each other to said inactive position;
• a spacer disposed between said cutting knives and in engagement therewith, said spacer being generally circular in transverse section and including two parallel, axially directed flattened portions, said spacer being fixed against movement along but rotatable about the longitudinal axis of said toolhead to move said knives away from each other against the action of the biasing means;
• a rectangular recess formed in said spacer, said recess having transversely directed guide edges parallel to said flattened portions of said spacer, a rotary and axially movable dog member including a drive portion disposed within said recess of said spacer, means in said toolhead supporting said dog member during rotation and axial movement thereof, spring means in said toolhead to normally bias said dog member axially toward said recess said dog member including side edges slidingly engaging said recess guide edges, the transverse extent of said drive portion being less than the transverse length of said recess, thereby to couple said dog and spacer for rotary motion while permitting limited floating movement of said parts when said flattened portions of said spacer are parallel to the direction of floating movement of said cutting knives, drive means for rotating said dog member and coupling means between said drive means and said dog member permitting limited axial movement of said dog member and limited transverse movement thereof, shoulder means in said toolhead for selective engagement with said dog member when it is in its retracted position against the spring means to retain the dog member against axial movement, a hand tool access opening in a face of the toolhead to permit a hand tool to be inserted therein to engage and manually shift said dog member axially and then transversely in the toolhead into engagement with said shoulder means wherein said drive portion is clear of said spacer, said cutting knives in the cleared position of said drive portion being removable from said toolhead.