Cincinnati FTV850-3700 Spindle Repair

The Cincinnati FTV850-3700 is a large CNC vertical machining center.  It can come fitted with this oil mist lubricated and pulley driven spindle that is capable of running up to 6,000 rpm.

CHALLENGE

Our customer sent in this Cincinnati FTV850-3700 spindle stating they were getting low drawbar pullforce.  Once the spindle arrived at Northland Tool we completed a full disassembly and evaluation.

This is what we found:

• We were only seeing about 1300Lbs of draw bar force. (Print specs 3300 Lbs.)
• The inside of the shaft was heavily corroded and rusted, one of the factors in the low force.
• The draw bar shaft was heavily corroded and we recommended it be replaced. (Pic 3)
• Ball cage was also heavily worn and needed to be replaced.
• The ( Shaft ID ) housing for the brass ball cage was corroded (Pic 2)
• All four bearings were worn and the rear bearing grease was contaminated with a dark brown grease (Pic 1)
• ID 50 Taper had poor contact and measured “AT wrong” on our air gauge
• The Bellevilles were worn
• The OD bearing journals had score marks

SOLUTION

The following actions were performed on this Cincinnati FTV850-3700 spindle:

• Replace Bolts, O-rings, Bearings, Bellevilles, Belt, Brass ball cage, and Draw bar
• Grind-Plate-Grind (GPG) ID 50 taper due to poor contact, low gap and failing on the air gauge system
• GPG ball cage housing in rear ID of shaft
• GPG tail of shaft where Belleville’s pilot due to heavy corrosion
• Polish OD bearing journals in assmembly

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.