Cincinnati Milacron Magnum 800 Spindle Repair

The Cincinnati Milacron Magnum 800 is a CNC horizontal machining center.  It comes equipped with a 50 HP spindle capable of running up to 6,500 rpm with a CAT 50 tool holder.13775-spindle


Our customer experienced a crash with their machine, causing damage to the interior of the spindle, as well as where it made contact with the workpiece.


Dimensional analysis revealed that critical components were out of spec. The tooling taper ID measured with severe runout of >50µ. The #2 bearing had started to weld to the shaft, which caused the surface to become uneven and resulted in damage to all of the journals as it was pressed off the length of the shaft.

Cincinnati Milacron Magnum 800 Spindle Repair

All of the interior bearings had become severely contaminated with black sludge – a mixture of lubricant, coolant, and material swarf. The gear began to heavily fret on the shaft causing a significant difference of >70µ clearance.


All components were thoroughly cleaned and refurbished. This repair required a full replacement of new bearings, bolts, o-rings and seal, and Belleville washers, and a gear was sent to a requalifying facility to be refurbished.

This repair required significant precision grinding work to bring critical dimensions back to OEM spec. A grind-chrome plate-finish grind process was performed on the three 100mm bearing journals, CAT50 ID taper, and the 90mm surface where the gear is located on the shaft. Additional light grinding was performed on the shaft nose OD to address minor cosmetic damage.

Cincinnati Magnum 800 Chrome-plated Shaft


After performing all dimensional work, the spindle entered the final stages of our repair process:

  • Adjust bearing preload
  • Reassemble entire spindle
  • Balance shaft
  • Break-in procedure
  • Pass quality control inspection

Every Northland Tool repair is backed by a 1-year warranty.

Cincinnati Magnum 800 Spindle Repair


  • Cincinnati Magnum 800 Spindle Crash

    Evidence showing where the tool-holding end of the spindle made contact when the machine crashed.

  • Cincinnati Magnum 800 Spindle Repair

    Marred surface of inner race of bearings caused fretting along journals as the ring was being pressed off the shaft.

  • shaft-fretting-spindle

    Fretting on the shaft where damaged inner race made contact along the length of the shaft.

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More Case Studies

Repair History - Here are examples of similar spindle repairs that may contain additional information that will help you. If you have additional questions, please contact us.

I really didn’t expect this; You guys really pulled it off! My many thanks to your outstanding crew for helping us get back into production.
— Dan Eaton, Taylor Metalworks
Its great not to be sending spindles out on a regular basis since you addressed my problems, but I know they will still be coming sooner or later. Never a problem when we get them back , run better than new. Hope everything is ok there. Please tell everyone there that we here appreciate everything that you do to keep us up and running and the quick turnarounds. Have delt with the rest now deal with the best. Have a great week end and up and coming holiday.
— Northland Customer
Thank you NTE just received spindle today and WOW ! what a nice job. Can’t wait to use it. Thank the Northland team for us for a job well done 
— Northland Customer
Both of the spindles that you repaired are on the machines and running great. We don’t have any spares for those grinders. We probably will not be purchasing a spare, as you have been able to turn around the repairs quickly and the price of a spare is cost prohibitive.
— Northland Customer
I am writing to thank Northland Tool for going the extra mile and saving my company from expensive machine downtime and expensive repairs. We have always sent our Chiron spindles for repair as a shaft with bearings. None of our previous rebuilders pointed out the bearing fretting or the fact that the housing in the machine was out of tolerance and causing premature failure to the spindles. After Northland fixed the housings the spindles have never sounded as good or run as well! Great job guys!
— Northland Customer
The detailed cause of failure reports and the expert technical advice that Northland Tool provides is bar none the best I have ever seen. We struggled to keep two of our large our milling spindles running for longer than 6 to 12 months. Northland Tools evaluation showed that the hydraulic nuts were not holding the assembly together causing premature spindle failure. We discussed this in detail and mutually decided to modify the spindle shaft to prevent this from occurring again. The first spindle we performed this on is still in the machine running like new after 3 years. That’s over three times the life of previous repairs and it’s still going strong. Easily over $40,000.00 of savings so far on that one machine and counting.
— Northland Customer
Your people go above and beyond the call of duty when it comes to spindle repair. When we had difficulty with the spindle installation and we were able to talk directly to a spindle technician that helped us troubleshoot the issue it helped us out of a bind. We have sent several spindles to you and have nothing but great things to say.
— Northland Customer
Thank you for your attention with my quick turn spindle repair. Your status updates allowed me to plan around machine downtime and I now know that you deliver on your promises. In the past other spindle repair vendors talked a big game and consistently failed to deliver. You not only delivered my spindle before the due date but you kept me informed throughout the entire repair process.
— Northland Customer
You performed a miracle with my BIG PLUS spindle. After crashing the spindle severely damaging the taper we found that a replacement spindle was not only cost prohibitive but had a long delivery. Your repair was a fraction of the cost of new and you never would know that the spindle was damaged to the extent it was.
— Northland Customer
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