Mazak HTC400 Expedited rebuild with machining & grinding


Mazak HTC400 - Oil mist lubrication, Coupling driven, 10,000 rpm

The bearings of this horizontal milling spindle were very noisy when rotated by hand incoming. The residual lubrication oil in the spindle was thick and contaminated, and the inside of the front cover was full of coolant residue and chips. All of the bearings felt worn when rotated, especially the #4 rear bearing. The tooling taper ID was damaged and bell-mouthed with runout >20µ. The integrated drive dogs were worn. The drive coupling was stuck on the shaft and the keys, key ways & t-bar slot were worn.


The spindle went to the machining & grinding side of the shop first so we could rework the drive dogs, keys, drive coupling key ways & t-bar slot. We also performed a green grind, chrome plate & finish grind of the tooling taper ID. After cleaning, we installed the bearings, o-rings & assembly screws. We adjusted the preload, assembled all components, then test ran and balanced the spindle before shipping to our customer. We advised our customer to check their spindle oil lubrication system for contamination & proper settings prior to reinstalling the spindle. This rebuild was accomplished on an expedited basis.

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