Abstract: A central cutting structure for use with a drill bit includes a plurality of cutters, of which at least one overlaps the center of a supporting member from which the cutters extend. Each cutter has a side rake angle that provides an overlapping relationship with at least one other cutter to provide an aggressive cutting surface for penetrating hard formations.

Abstract: A drill bit, insert and method useful for subterranean drilling, or forming boreholes in subterranean formations is provided. More particularly, a more efficient cutting structure and method is provided in the central portion of a PDC drill bit. The present invention provides a drill bit, insert and method having a central cutting portion with a more normalized angle of attack. The drill bit of the present invention provides for various attack angles much closer to the optimum side rake.

Abstract: A mold usable to form a drill bit body and a method for forming such a mold are disclosed. A shell is provided, the shell having a cavity. Fusible material, such as foundry sand, is provided into the cavity, then fused to form a solid insert within the shell. The solid insert is then modified, such as by machining, to form a mold having features usable to form a drill bit body having desired characteristics. Materials for forming the drill bit body can then be provided into the mold, for heating and cooling. Then, the drill bit body and mold can be removed from the shell. The shell is thereby reusable, while the mold, being formed from inexpensive fusible materials, can be removed or destroyed, if necessary, to free the drill bit body.

Abstract: A drill bit, insert and method useful for subterranean drilling, or forming boreholes in subterranean formations is provided. More particularly, a more efficient cutting structure and method is provided in the central portion of a PDC drill bit. The present invention provides a drill bit, insert and method having a central cutting portion with a more normalized angle of attack. The drill bit of the present invention provides for various attack angles much closer to the optimum side rake.

Abstract: An integral generally channel-form runner for securing and supporting one or more wallboard panels in a demountable structure, the runner having an integral support for the lower edges of the wallboard panels in a position spaced above the bottom of the runner to prevent absorption of water and formation of mildew at the edges of the wallboard panels.