Hitachi Seiki HT-20 Spindle Repair

Hitachi Seiki Spindle Repair

Hitachi Seiki was a Japanese builder of CNC milling and turning machines targeted at the automotive manufacturing market until the[...]

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Hitachi Seiki was a Japanese builder of CNC milling and turning machines targeted at the automotive manufacturing market until the demise of the company in 2002. Although Mori Seiki took over the machine tool line and briefly produced several machines under the Mori Seiki Hitech nameplate, support for the original Hitachi Seiki machines was extremely limited.

Northland Tool & Electronics has been supporting Hitachi Seiki spindles since the beginning (over 30 years!) and we have amassed prints, parts and the knowledge to repair most types of Hitachi Seiki spindles. This allows us to guarantee quick turn around on the spindle repair to make sure you are up and running in the shortest time period possible.


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Upon arrival, every spindle is logged into our production tracking software system. Any issues associated with incoming condition as related to transit are noted.[...]

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The spindles are prioritized and moved to either the disassembly technicians or to the spindle run-up room, depending on the circumstances. Our techs carefully break down the spindle into its component parts while meticulously noting their general condition as well as specific damage to them. They also photograph the process and perform a full dimensional inspection to identify excessive wear which may help identify the cause of failure.

Once the initial disassembly and evaluation are completed, the spindle is given a second look by our production manager who reviews & completes the evaluation. He will identify the mode of failure and all pertinent issues, as well as recommended corrective actions. Many evaluations are not complete until the production manager consults with the head of our grinding & machining department. We often have recommendations for additional steps the customer can take to prevent premature spindle failure in the future. We call on our 30 plus years of experience rebuilding spindles to come to these conclusions.

After our purchasing department sources all replacement part costs & lead times, the quote is generated, given a final check and communicated to the customer for approval. Once we have received the approval, production is scheduled and parts are ordered. All spindle parts are carefully cleaned and any grinding or machining operations are completed. Only when all components are available and qualified does the spindle proceed to our spindle assembly technicians. These highly trained professionals assemble all the spindle components and then perform a rigorous break-in process which may include dynamic balancing as well as thermal & vibration analysis depending on the type of spindle. After a final quality control check is performed, the spindle is given back to our shipping department, carefully boxed to minimize the possibility of in-transit damage and shipped back to you, our customer. Hide Details

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At Northland, we take pride in our expert knowledge of every brand we repair-please see the list of models we repair below. If you do not see your particular model please contact us, we have probably repaired one just like it in our over 30 years of spindle rebuilding:

  • Hitachi Seiki HC400A
  • Hitachi Seiki HC630
  • Hitachi Seiki HC800
  • Hitachi Seiki HG500
  • Hitachi Seiki HG800
  • Hitachi Seiki HG400II
  • Hitachi Seiki HG500II
  • Hitachi Seiki HG630II
  • Hitachi Seiki HG400-III
  • Hitachi Seiki HS300
  • Hitachi Seiki HS500
  • Hitachi Seiki HS630
  • Hitachi Seiki VA40
  • Hitachi Seiki VA50
  • Hitachi Seiki VK45
  • Hitachi Seiki VK55
  • Hitachi Seiki VK65
  • Hitachi Seiki VK85
  • Hitachi Seiki VK45-II
  • Hitachi Seiki VK55-II
  • Hitachi Seiki VK65-II
  • Hitachi Seiki VM40
  • Hitachi Seiki VM50
  • Hitachi Seiki VM40-II
  • Hitachi Seiki VM40-III
  • Hitachi Seiki VS50
  • Hitachi Seiki VS50 B
  • Hitachi Seiki VS60
  • Hitachi Seiki MACC MATIC 48VGb
  • Hitachi Seiki MG 2500-H
  • Hitachi Seiki 2ML-9
  • Hitachi Seiki 2ML-P
  • Hitachi Seiki MS-400H


One of the most common causes of failure on Hitachi Seiki spindles is excessive wear of the mating parts of the rotary union which can allow through-spindle coolant to find its way to the interior of the spindle. This condition if ignored can cause not only bearing failure, but can also make it necessary to grind, plate & finish grind one or more bearing journals and in some cases rewind of the stator.

To avoid this failure replace the worn rotary union parts during every spindle change. You should also be sure that the pressure in your rotary union system is up to specification. Insufficient pressure will result in the two precision-ground mating surfaces of the rotary union not being forced together enough to prevent leakage.

  • Rotary Union Failure One of the most common causes of failure on Hitachi Seiki spindles is worn rotary union parts. This causes the through tool coolant to leak from its passageway and it often time finds its way to the interior of the Hitachi Seiki spindle. This causes bearing failure and stator damage. It is not uncommon that failures due to rotary union failure involve a stator rewind and grind plate grind to the bearing journal. To avoid this failure replace the worn rotary union parts during every spindle change. You also want to make sure the pressure in your rotary union system is up to specification. Reduced pressure can cause leakage, as the two mating parts of the rotary union will not be forced together enough to prevent leakage.
  • Spacer Damage From Loss of Preload Spacer damage can occur if bearing preload is lost or if the spindle is run after bearing damage has occurred. Depending on the severity of the damage the repair of the spacer can range from rework to manufacture of replacement parts.
  • Shaft Fretting When two mating parts, in this case the spindle shaft and pulley, are not within specification fretting will occur. The evidence of this is the brown almost rust colored discoloration. This area of the shaft was worn down from the micro machining that occurs when the two parts are allowed to move against each other. The shaft in this particular spindle repair was undersized and needed to be ground plate ground to bring it back to OEM tolerance.
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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