Downhole tool and method of manufacturing a tool
Producing a drag bit includes creating a mold corresponding to the surface of the bit and inserting a core in the mold corresponding to the plenum of the bit. A preliminary shaped bit is cast in the mold. Excess material is removed from the casting to produce a final shaped bit.
1. A steel casting for a tool to drill a borehole includes:
a body;
blades extending from the body; and
a plenum in the body;
wherein the blades are machined to a final dimension and the plenum includes extensions to limit the mass of the body at the root of each blade.
2. The steel casting of claim 1 wherein the extensions to limit the mass of the body at the root of each blade extend helically with the root of the blades on the body of the bit.
3. The steel casting of claim 1 wherein the steel casting is heat treated prior to machining to reduce hardness.
4. The steel casting of claim 1 wherein the steel casting is heat treated after machining to increase hardness.
5. The steel casting of claim 1 wherein the steel material of the casting is selected for compatibility with corrosive materials encountered in boreholes.
6. The steel casting of claim 1 wherein threads are machined on the cast bit body for mounting the tool to a drill string.
7. The steel casting of claim 1 wherein the tool is a drag bit.