Standard Open Roller Bearing-
Standard open roller bearings are bearings without a seal. This means that the bearings are open to outside debris, which can enter through the cone.
The advantage of an open bearing bit is that they are usually cheaper. They are ideal for drilling shallow holes, in the hundreds of feet. If drilling deeper holes with an open bearing bit you will probably have to pull it out every couple hundred feet to clean out the debris in the cones to free them up.
Air Blast Bearings are equipped on Air Circulation Bits. These bits have air passages that supply air to the bearings for cooling and lubricating of the bearing, and for cleaning of the bearing from the drilling debris.
Sealed Roller Bearings have some of the features of the non-sealed open bearings, but longer lifetime because the bearings are sealed with an O’ Ring Seal.
A lubrication and compensator system prevents leakage into the bearing system and stops the possibility of debris blocking the bearing as well as leakage of grease.
Sealed Journal Bearings have very good durability and wear resistance. Instead of rollers inside the cone there is a floating bushing.
The bushing is usually made out of special material that is highly resistant to heat and galling (surface damage).