Abstract: A boring head having a diametrical bore adjacent the working end thereof for insertion and removal of two or more interchangeable cutter holders. The cutter holders are restrained against rotational movement within the bore but not axial movement, whereby rotation of a first drive member having threaded engagement with an internally threaded longitudinal bore in the cutter holder will cause radial adjustment of the cutter holder relative to the boring head. Rotation of the first device member is accomplished by rotation of a second drive member having a gear drive connection with the first drive member. A first micrometer dial on the outer end of the first drive member provides for rough orientation of the cutter holder during such radial adjustment thereof, whereas a second micrometer dial on the outer end of the second drive member provides for extremely precise measurements of such radial adjustment.

Abstract: Tool includes a plurality of circumferentially spaced radially extending guideways in an end face thereof for receipt of a corresponding number of cutting tool holders. The radial inner ends of the holders have cam followers thereon which are urged radially inwardly by spring members into engagement with one or more correspondingly tapered cam surfaces on a central pusher element. The pusher element is supported for axial movement within a longitudinal bore in the cutting tool and is precisely axially movable in opposite directions to cause precise radial inward and outward movement of the tool holders within such guideways.