Heavy-duty live centers

The method of forming and making a heavy-duty live center having a workpiece capacity of 35 tons and greater, the steps including:

• (a) forming a hollow quill of determined configuration;
• (b) forming and supplying a rotatable spindle and carrying this spindle in the bore of the quill and with this quill in mounted condition having a work load supporting and extending beyond the quill and shaping the intermediate portion of the spindle so as to provide sufficient clearance between the bore and spindle allowing the spindle to bow with the application of a heavy load and when bowed by this load the spindle turns freely in the quill;
• (c) supporting and mounting a self-aligning roller bearing on the foreportion of the spindle and adjacent thereto and to the rear thereof supplying and mounting a self-aligning spherical roller thrust bearing;
• (d) forming a front bore in the quill with the front portion of the bore being precisely sized to receive and retain the outer race of the self-aligning roller bearing, and to accommodate the outer race of the spherical roller thrust bearing additionally forming the rear portion of this front bore to a determined amount oversized in its diameter with respect to the diameter of the outer race of this thrust bearing, and forming the rear of this front bore to provide a face surface normal to the axis of the bore, this face surface providing a stop surface for the rear face of the outer race of the thrust bearing;
• (e) providing and mounting antifriction bearing means on the rear of the spindle and carrying this bearing means in the bore of the quill, this bearing means adapted to receive and support the rear of the spindle;
• (f) providing a biasing means on the rear of the spindle and in association with the bearing means this biasing means provides a determined preload to the bearings carried in the front bore of the quill;
• (g) providing a shoulder on the foreportion of the spindle, said shoulder adapted to engage the inner race of the self-aligning bearing and as urged by the applied preload the spindle and this bearing is drawn rearwardly and as this bearing is moved rearwardly its inner race moves the inner race of the spherical roller thrust bearing rearwardly to cause the outer race of the thrust bearing to be brought into sliding engagement with the inner rear face surface of the front bore, and (h) providing a sealing means in association with the spindle and front bore of the quill to close the front bore to dirt, coolant and the like and retain the grease in the bearings without contamination and when a heavy load is placed on the extending end of the spindle, the spindle is bowed in accordance with the load and the stiffness of the spindle, the self-aligning bearing moves into adjusted alignment with the bowing of the spindle and said outer race of the thrust bearing moves in the enlarged bore an amount equal to the bowing of the spindle at the inner race of the thrust bearing, this displacement of the thrust bearing from the theoretical center line of the bore and to the center line of the bowed spindle enabling the thrust bearing to equally accept the end thrust on the spindle while the radial bearing is also aligned with the bow of the loaded spindle.