Cutting tools

A cutting tool for incising a helical cut around the internal surface of a hollow member comprising:

• tool carrier means for insertion into the hollow member adjacent the internal surface thereof to be cut, the tool carrier means comprising a shaft with its longitudinal axis aligned parallel to the axis of relative rotation of the tool and the hollow member;
• cutting block means carried by the tool carrier means and extending generally axially thereof, the block means being freely pivotally mounted on the carrier means about an axis offset from and normal to the axis of the shaft;
• and a cutting member secured to the cutting block means and extending from the block means with its longitudinal axis generally parallel to the axis of pivot thereof upon the carrier means and approximately intersecting the axis of the shaft normally thereto, whereby as the tool moves in a helical path around the internal surface, the cutting edge of the cutting member moves in a direction generally towards the axis of the pivot of the cutting block means on the shaft;
• whereby in cutting use the cutting block means turns on its pivotal connection on the tool carrier means such that the cutting member is aligned with and cuts at a helical angle determined by the relative rotational and axial speeds of the hollow member and tool during cutting.