GMN TSSV120 Spindle Repair


GMN TSSV-120, 42,000 RPM motorized grinding spindle, oil/air mist lubrication, quill pilot

This spindle had axial end play incoming, indicating a loss of preload. The shaft tooling pilot had very high runout (>36µ) and the pilot face was chipped. Our internal evaluation showed contamination with grinding swarf. Also, the rear ID of the main housing where the ball cage locates was egged & oversized with dings from the balls because the slide fit was so loose.


We completed a grind, chrome plate & finish grind of the spindle shaft to restore the tooling interface to top condition. We also undertook a G/P/G of the rear housing ID to remedy the wear and damage which contributed to the overall failure of this spindle. The spindle was reassembled with new high-speed ceramic bearings, o-rings & assembly screws and then run up and balanced in our test room.


Even though the TSSV has been replaced in the GMN grinding spindle line, we enabled our customer to avoid paying top dollar for the newer model. Their rebuilt spindle with all new internal rolling elements and all critical dimensions restored will perform at peak efficiency.


  • GMN spindle disassembled and ready for cause of failure evaluation.

  • This stator is encased in resin to help protect it from contamination causing electrical issues.

  • The ball cage assembly being removed from the rear of the spindle. The ball cage allows axial movement of the shaft caused by heat growth. Without the ball cage the shaft would heat up from normal use, expand and over preload the bearings causing spindle failure.

  • This is the chip in the front tooling face found during evaluation.

  • Clogged coolant jacket. We remove all coolant jackets from the main housings and this is a great example of why we do it. No coolant was able to circulate around the stator. The heat generated from the stator will no longer be carried away and will eventually cause the stator windings to deteriorate.

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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