Hitachi Seiki HT-20 Spindle Repair

The Hitachi Seiki HT-20 is a CNC turning center and the HT in the name stands for Hightech-turn.  This machine can come equipped with this grease lubricated and belt driven spindle that is capable of running up to 3,600 rpm.

CHALLENGE

When this Hitachi Seiki HT-20 spindle arrived at Northland Tool and Electronics, our incoming test runs confirmed our customer’s indication of noisy bearings.  After a complete breakdown, we noted that there was gear oil contamination with metal particulate in the spindle.  The oil had contaminated the work shaft bearings as well and the grease in almost all of the bearings had been completely washed out.  We then evaluated all critical dimensions and found that the taper and face of the work shaft were in poor condition.  Both had high runout and the key was damaged and stuck in the keyway.  Lastly, the rear nut of the drive shaft was damaged and all the oil lines were deteriorated and contaminated.  No other dimensional deviations were noted for this repair.

SOLUTION

The following actions were performed on this Hitachi Seiki HT-20 spindle:

• Clean, inspect overall dimensions
• Fabricate and install new work shaft key
• Kiss grind the work shaft taper and face
• Replace all bearings, drive shaft nut, and oil lines
• Replace seals, o-rings, lock washers, and assembly screws

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.