Abstract: A ball-bearing unit for a bearing of a deep-drilling apparatus having bearing races made from steel with balls disposed therebetween. Contaminated drilling medium passes into the space between the bearing races. Load-bearing balls made from ceramic alternate with separating balls of smaller diameter made from steel between the bearing races to extend significantly the service life of the ball-bearing unit.

Abstract: A ball-bearing unit for a bearing of a deep-drilling apparatus having bearing races made from steel with balls disposed therebetween. Contaminated drilling medium passes into the space between the bearing races. Load-bearing balls made from ceramic alternate with separating balls of smaller diameter made from steel between the bearing races to extend significantly the service life of the ball-bearing unit.

Abstract: A mounting plate for belt tensioning or guide rollers, or the like, which includes an attachment place generally more centrally disposed along the mounting plate at which the roller is supported and at least two tensioning places at opposite sides of the attachment place for the roller. The plate being attached to a mounting housing at the tensioning places. The plate having resting surfaces protruding from it toward the housing to which the plate is mounted and the resting surface in the attachment place in the region of the tensioning roller protrudes to a greater height than the resting surfaces at the tensioning places for assuring support of the roller against the housing. In another version, the mounting plate is slightly V shaped or concave, with the two tensioning places being on one arm of the V and the attachment place in the region of the tensioning roller on the other arm of the V.