Johnford SV-45H Spindle Repair

The Johnford SV-45H is a CNC vertical machining center.  It comes fitted with a grease lubricated and pulley driven spindle capable of running up to 8,000 rpm.

CHALLENGE

This Johnford SV-45H spindle was seized incoming.  After disassembly we noted that the front bearings appear to have lost preload from a previous crash.  The #2 bearing rubbed out on the inner bearing spacer causing damage to the spacer.  The pulley shoulder was worn and the shaft has light fretting on front bearing, sensor ring, and pulley journals.  We also noted that the shaft tooling taper had spot wear, poor tool contact, and had 3-4µ runout.  Lastly, the collet fingers are worn and the front of shaft had deep-drilled balance holes on the OD which almost reach the taper. Similar holes on sensor ring OD.  No other dimensional deviations were noted for this repair.

SOLUTION

The following actions were performed on this Johnford SV-45H spindle:

• Clean, inspect overall dimensions
• Kiss grind the shaft tooling taper and pulley shoulder
• Rework bearing spacers for parallelism and to remove rubout damage
• Replace bearings, collet assembly, bellevilles, o-rings, and assembly screws
• Customer to supply front cover, cooling jacket, rear pulley nut, and rear bearing nut

RESULT

After reassembly of all components, adjusting bearing preload, and undergoing break-in and testing procedures, this spindle passed our final quality inspection before being returned to our customer with a 1-year warranty.