Ball hole welding using the friction stir welding (FSW) process
A roller cone drill bit includes a bit body, at least one leg extending downward from the bit body, a journal on each leg, and a roller cone mounted on each journal. A ball race is configured between each journal and roller cone, and a plurality of retention balls is disposed within each ball race. A ball hole extends from the back face of each leg to the ball race, and a ball hole plug fits within the ball hole. The ball hole plug is secured to the leg by a friction stir weld.
1. A method for retaining a roller cone on a bit leg, comprising:
mounting a roller cone on a journal extending downward from the bit leg;
inserting a plurality of retention balls into a ball hole extending through a leg back face to the journal;
inserting a ball hole plug into the ball hole;
covering the ball hole plug with a plate; and
friction stir welding the ball hole plug and the plate to the leg back face.
2. The method of claim 1 , further comprising providing an additive material and friction stir mixing the additive material into the bit leg.
3. The method of claim 1 , wherein the ball hole plug is friction stir welded to the bit leg prior to friction stir welding the plate.
4. The method of claim 1 , wherein the ball hole plug comprises a non-cylindrical head and the ball hole is non-cylindrical near the back face of the bit leg.
5. The method of claim 1 , further comprising welding a plurality of bit legs together.