Mori Seiki LL-7 Spindle Repair

This Mori Seiki LL-7 spindle is the tailstock spindle off of this very large flat bed lathe.  It is lubricated by an oil bath and is capable of running up to 1,150 RPM.

CHALLENGE

Our customer sent in this Mori Seiki LL-7 spindle stating a nut had backed off allowing the shaft to move.  When the spindle arrived at Northland Tool we saw right away that the rear nut was loose and had rubbed on the brass cover.  We then completed a full disassembly of the spindle and recorded a few issues.

Rotating parts laid out for evaluation

First, the front shaft locking nut had rubbed on the front cover causing heat damage to both parts.  All of the internal spacers were damaged and no longer flat.  Lastly, the ID Morse taper had high runout and looked visibly poor.  We also noted that the rear nut is set deep in the housing and will require a tool to be tightened properly during assembly.

SOLUTION

The following actions were performed on this Mori Seiki LL-7 spindle:

• Clean, inspect overall dimensions
• Replace bearings, bolts, and seal
• Machine off damage on front shaft nut
• Machine off damage on front cover
• Fabricate tool for rear nut installation
• Manufacture replacement spacers
• Kiss grind Morse Taper

RESULT

After reassembly of all components and adjusting bearing preload, we put the spindle through a rigorous break-in and testing procedure to make sure it passes our final quality inspection. See below for the passing test reports:

Front Bearings Vibration Analysis Spectrum:                 Rear Bearings Vibration Analysis Spectrum:

This spindle passed our final quality inspection and was returned to our customer with a 1-year warranty.