Bearings for downhole tools, downhole tools incorporating such bearings, and related methods

An earth-boring tool configured for use in a subterranean formation, comprising at least the following components:

• a tool body including at least one head;
• and
• a rolling cutter mounted on the at least one head;
• and
• a bearing system disposed between the at least one head and the rolling cutter mounted on the at least one head, the bearing system including:
• a head washer disposed on the at least one head;
• an at least substantially planar shaft washer retained within the rolling cutter and disposed around the at least one head;
• a first plurality of bearings disposed between the head washer and the at least substantially planar shaft washer;
• a rolling cutter washer retained within the rolling cutter;
• and
• a second plurality of bearings disposed between the at least substantially planar shaft washer and the rolling cutter washer;
• wherein the at least substantially planar shaft washer is directly interposed between, and in contact with, the first plurality of bearings and the second plurality of bearings.

A method of forming an earth-boring tool configured for use in a subterranean formation, comprising:

• inserting a tensioner bolt into a rolling cutter;
• inserting a rolling cutter washer into the rolling cutter;
• providing a plurality of bearings on the rolling cutter washer within the rolling cutter;
• inserting a substantially planar shaft washer into the rolling cutter such that the bearings of the plurality of bearings are disposed between the rolling cutter washer and the at least substantially planar shaft washer;
• providing a retaining member within the rolling cutter to retain the at least substantially planar shaft washer, the plurality of bearings, the rolling cutter washer, and the tensioner bolt within the rolling cutter;
• positioning a head washer over and around a head of a tool body of the earth-boring tool;
• providing an additional plurality of bearings on the head washer, such that the at least substantially planar shaft washer is directly interposed between, and in contact with, the bearings on the rolling cutter washer and the additional plurality of bearings on the head washer;
• positioning the rolling cutter on the head such that the tensioner bolt extends through the head, and the plurality of bearings on the rolling cutter washer is disposed between the head washer and the at least substantially planar shaft washer retained within the rolling cutter;
• and
• securing the tensioner bolt to the head to secure the rolling cutter to the head and tensioning the tensioner bolt to compress the additional plurality of bearings between the head washer and the at least substantially planar shaft washer, and to compress the plurality of bearings between the at least substantially planar shaft washer and the rolling cutter washer.