The cutter head of a tunnelling machine is mounted for rotation about the axis of the tunnel and has a face extending on a plane perpendicular to that axis. The cutter head serves as a mount for a plurality of roller cutters, each of which is mounted in a box like saddle member fixed to the cutter head. Each roller cutter includes a frame having a shaft on which the roller cutter is journalled and a pair of end members which fit in recesses on the inside of the saddle member. These recesses open toward the rear of the cutter head to allow removal and replacement of cutters and cutter frames from the rear face of the cutter head. Each cutter frame is held in place by a wedge member on each side of the saddle and wedge members, one on each side, engage mating wedge surfaces on the saddle and the adjacent end member of the cutter frame so that movement of each wedge member by a jack screw in a direction transverse to the axis of the roller forces each end member forwardly in its recess. Suitable clamp bolts extending along an axis parallel to the roller axis extend through the wedge member to make threaded engagement with the saddle to hold the wedge members in place.

In the saddle structure of the improved drill bit cutter assembly of the invention both spaced-apart legs are provided with bores each extending through the leg to receive a clamping bolt. These bores extend in directions including between them an angle of up to 90.degree.. The shaft-receiving recess, between the legs, has a polygonal shape complementing that of the end portion of the shaft.

A roller cutter assembly adapted to be fixed to the cutter head of a tunneling machine is disclosed. The cutter assembly includes a cutter rotatably mounted on a shaft so that end portions of the shaft project from the cutter. Each of those projecting end portions has a pair of flat faces the planes of which intersect at an angle of 90.degree.. A generally U-shaped saddle having projecting arm portions mounts the shaft so that the cutter is rotatable on the shaft. Each arm of the saddle has a pair of flat faces the planes of which intersect at an angle of 90 degrees and which engage the faces on a projecting end portion of the shaft. The engaged faces are clamped together by bolts, each of which exerts a clamping force having components normal to the engaged faces and each of which is more nearly horizontal than vertical with respect to the intended cutting plane. According to one aspect of this invention, the cutter is a gauge cutter and one projecting arm portion of the saddle may be removed from the remainder of the saddle to facilitate removal and replacement of the gauge cutter.

A raise boring head which includes a plurality of rolling cutters distributed over the head and including circumferentially spaced gauge cutters. Each cutter has a rotatable part and a support shaft supporting the rotatable part with the ends of the support shafts carried in saddles fixed to the body of the raise boring head. Each end of each support shaft is formed to a rectangular shape and fits into a rectangular slot in the respective saddle and is secured therein as by bolts. The radially outer sides of the saddles for the gauge cutters are provided with hard wear resistant inserts to reduce the wear thereon.

A rock-boring machine of the type comprising rotatable headplate having a plurality of cutting units mounted on the front face of the headplate. Each cutting unit includes a cutter journalled for rotation on a shaft. The ends of the shaft are hexagonal in cross-section and are supported in complementally-slotted saddles to prevent rotation of the shaft in the saddles. The shaft is locked in the saddles by means of a single locking member at each end of the shaft. Each locking member is secured to a saddle and is adapted to bear against one of the surfaces of the hexagonal ends of the shaft.