A well drilling head comprises a housing and a bearing assembly. The housing has a sidewall structure defining a central bore. A tapered bearing assembly seating surface is provided within the central bore of the housing. The bearing assembly includes an outer barrel having a central bore, an inner barrel at least partially disposed within the central bore of the outer barrel and bearing units coupled between the barrels for providing concentric alignment of the barrels and allowing rotation therebetween. The outer barrel is removably seated within the central bore of the housing. A tapered exterior surface of the outer barrel is engaged with the tapered bearing assembly seating surface of the housing whereby engagement of the tapered surfaces align the outer barrel with respect to the central bore of the housing.