Bearing clearance arrangement in a tricone bit

A leg assembly of a tricone bit comprising:

• a leg comprising:
• a first row of bearings,
• a second row of bearing,
• a third row of bearings,
• an axis defining an axial center of rotation,
• a first inner raceway disposed at a distal end of the leg,
• a second inner raceway disposed at a middle section of the leg, and
• a third inner raceway at a proximal end of the leg;
• and
• a cone rotatably mounted on the leg to rotate about the axis, the cone comprising:
• a first outer raceway having a first outer diameter and forming a first raceway with the first inner raceway, the first inner raceway containing the first row of bearings,
• a second outer raceway having a second outer diameter and forming a second raceway with the second inner raceway, the second raceway containing the second row of bearings, and
• a third outer raceway having a third outer diameter and forming a third raceway with the third inner raceway, the third raceway containing the third row of bearings, the third outer diameter smaller than the first outer diameter,
• wherein a first clearance for the first row of bearings in the first raceway is less than a second clearance for the second row of bearings in the second raceway, the first clearance radially extending from the axis between the first inner wall and the first outer wall, the second clearance radially extending from the axis between the second inner wall and the second outer wall, and the second clearance is less than a third clearance for the third row of bearings in the third raceway, the third clearance radially extending from the axis between the third inner wall and the third outer wall, and
• wherein, in response to a radial load applied to the tricone bit during a drilling process, the first row of bearings contacts the first inner raceway and the first outer raceway, and supports the radial load.

A tricone bit comprising three leg assemblies, each leg assembly comprising:

• a cone;
• and
• a leg fitting inside the cone, the leg having an axis defining an axial center of rotation of the cone, the leg comprising:
• a first raceway disposed between the cone and the leg at a distal end of the leg assembly and formed by a first inner wall disposed on the leg and a first outer wall defined by the cone, the first raceway containing a first row of bearings between the first inner wall and the first outer wall,
• a second raceway disposed between the cone and the leg at a middle section of the leg assembly and formed by a second inner wall disposed on the leg and a second outer wall defined by the cone, the second raceway containing a second row of bearings between the second inner wall and the second outer wall, and
• a third raceway disposed between the cone and the leg at a proximal end of the leg assembly and formed by a third inner wall disposed on the leg and a third outer wall defined by the cone, the third raceway containing a third row of bearings,
• wherein:
• a first clearance for the first row of bearings in for the first raceway is less than a second clearance for the second row of bearings in the second raceway, the first clearance radially extending from the axis between the first inner wall and the first outer wall, the second clearance radially extending from the axis between the second inner wall and the second outer wall,
• the second clearance is less than a third clearance for the third row of bearings in the third raceway, the third clearance radially extending from the axis between the third inner wall and the third outer wall, and
• the first row of bearings supports, in the first raceway, a radial load applied to the tricone bit during a drilling process.