In an embodiment, a disc cutter for use on a tunnel boring machine may include a shaft and a cutter assembly rotatably mounted on the shaft. The cutter assembly may include a cutter ring extending circumferentially about a central axis and one or more bearing apparatuses rotatably mounting the cutter assembly to the shaft. Each bearing apparatuses may include a rotor extending circumferentially about the central axis and a first plurality of superhard bearing elements distributed circumferentially about the central axis. Each first superhard bearing element may be attached to the rotor and may include a bearing surface. The bearing apparatuses may further include a stator extending circumferentially about the central axis and a second plurality of superhard bearing elements attached to the stator that are generally opposed to the first plurality of superhard bearing elements of the rotor.