Hwacheon lathe with poor part finish


Our customer sent this turning center spindle in for rebuild because of poor part finish & excessive bearing noise. The front tapered roller bearing failed from contamination with coolant which had washed out almost all of the grease & allowed corrosion of the rolling elements & raceways. The contaminant had also largely displaced the grease in the rest of the bearing complement, including the rear tapered roller. Our dimensional inspection also showed slight damage on the tooling taper OD & face. We did notice that both the front & rear housing ID’s were on the loose side of ISO, but there was no fretting which would indicate that this condition contributed to the bearing failure. As the housing bores were likely manufactured this way, we did not recommend grind, plate & finish grind to tighten them up.


We first performed a kiss grind on the tooling taper OD and face to remove the high spots. We replaced the full bearing complement, a worn pulley retention nut and the assembly hardware. When our customer initially contacted us about this spindle, they asked if we perform a run-in cycle which would be sufficient to break in the new bearing grease. Especially with tapered roller bearings, the spindle must be run in to disperse the grease and prevent overheating due to churning. According to our standard break-in procedure, we ran in this spindle at progressively increasing speeds for a total of eight hours while checking the vibration signature, then balanced the spindle with all rotating components installed, and shipped it to our customer ready to make parts.


  • Compromised rolling elements

  • Front roller bearing

  • Front roller bearing outer race

  • Damage to the face that needed to be finish ground

  • Damage to the taper that needed to be finish ground

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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 Sandy, Louis and your outstanding crew for helping us get back into production.

Dan Eaton, Taylor Metalworks

Lou all in all everything is running good. Just had a call from Sandy just the other day, its funny great minds think alike. 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 Debbie 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