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Cincinnati Arrow 750 Spindle Repair

The Cincinnati Arrow 750 is a CNC vertical machining center. It comes fitted with a grease lubricated and pulley driven spindle capable of running up to 6,000 rpm.

CHALLENGE

This Cincinnati Arrow 750 spindle was very sluggish, hard to rotate by hand, and had slightly high runout incoming. Upon inspection, we noted that the 40 ID Taper was visually poor, with metal chips found jammed up into the gripper pocket. The coolant contamination had washed out most of the grease from all three bearings. It appears that the coolant passed by the front cover seal and inner spacer o-rings. We then measure the critical dimensions and found three main issues. First, the front shaft shoulder had high runout (+9/+11, ISO +/-4µ). Second, the shaft 40 ID taper was bell mouthed and had slightly high runout (3µ). Third, both front and rear housing bores were severely egged and out of ISO (Front -8/+22µ, Rear -3/+10µ). No other significant dimensional deviations were noted (bearing journals/shoulders, housing bores).

SOLUTION

The following actions were performed on this Cincinnati Arrow 750 spindle:

Clean, inspect overall dimensions
Replace bearings, bolts, o-rings, front cover gasket, bellevilles, and gripper balls
Grind, chrome plate, and finish grind (GPG) the 40 ID Taper
GPG the front and rear housing bores
Kiss grind the front shaft shoulder

RESULT

After reassembly of all components, adjusting bearing preload, and undergoing break-in and testing procedures, this spindle passed our final quality inspection before being returned to our customer with a 1-year warranty.

DETAILED CAUSE OF FAILURE

Contaminated bearings
Rotating parts laid out for evaluation

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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.

Your staff is amazing. I dropped off my spindle at the repair facility and I was met by four guys in the shipping and receiving department and they absolutely understood what I needed for my little woodworking spindle it was fixed properly. Everyone was professional machine is back up and running, it works properly no play, not overheating. The machine now cuts better with less noise. I saw other spindles there from Hubble telescope and an aircraft facility. I knew I was in good hands.

— Scott Masi, Chairman Of Maine

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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