The Design of Rolling Bearing Mountings

20 Tailstock spindleOperating dataMaximum speed n = 3,500 min –1Cylindrical roller bearings have a high radial loadcarrying capacity, and angular contact ball bearingswith a 40° contact angle have a high axial load carryingcapacity.Bearing selection, dimensioningThe bearing arrangement must be particularly rigidand have a high load carrying capacity. Other requirementssuch as precision and high-speed suitability aremet by bearings of precision design.At the work end the high radial load is accommodatedby a double-row cylindrical roller bearing FAGNN3014ASK.M.SP. The high axial load is accommodatedat the opposite end by four angular contact ballbearings FAG 7210B.TVP.P5.UL. Three of these bearingsare mounted in tandem arrangement; the fourthbearing is merely for axial counter guidance.The maximum bearing O.D. is dictated by the size ofthe quill.Bearing clearanceThe cylindrical roller bearing with a tapered bore ispreloaded with 2...3 µm by pressing the inner ring onto the tapered shaft seat (taper 1:12).The angular contact ball bearings of universal designUL have a light preload in the O arrangement. The twospacers are identical in width and exclusively serve toprovide a cavity which can accommodate the excessgrease escaping from the bearings.Lubrication, sealingThe bearings are lubricated for life with FAG rollingbearing grease Arcanol L135V. A labyrinth seal preventsdirt from penetrating into the bearings.Machining tolerancesBearing Seat Diameter Form tolerance Axial runout tolerancetolerance (DIN ISO 1101) of abutment shoulderShaft, tapered Taper 1:12 1.5 µm 2 µmCylindrical roller bearing Housing –13 / +2 µm 2.5 µm 4 µmShaft –4 / +4 µm 1.5 µm 2 µmAngular contact ball bearings Housing –4 / +6 µm 2.5 µm 4 µm20: Bearing arrangement of a tailstock spindleFAG 32