replacing CNC mill spindle bearings

[OC_]

Ok, so I’m pretty damn new to cnc machining centers and I’m having what looks to be a major problem with the one I use. I use an old Kiwa 510 colt which is in mint-condition and belongs to my university. This machine is basically new, it probably has less then 50 hours since bought in 1991-92. I am the first one to really use it because the machine wasn’t parametered correctly and didn’t have complete manuals. No one really sat down, like I did, to figure it out. Instead, other people used a different machine tool we have (which is not as good).

Anyway, its giving tell tail signs of bearing failure and I have a few questions concerning this problem;

What might have caused this failure? Could the bearings have taken a ‘set’ from not being used the past 15 or so years? Could they have overheated? They started to make noise right at the end of a huge 2 day project.
Another thing about this; when I got the machine going I made sure to check all the oil’s, but there is one listed that I could not find. The manual calls to check the spindle oil cooler, but I can’t find it anywhere! The diagram shows the oil cooler as a separate unit off to the side of the machine. But it’s nowhere to be found!

Lastly, are these bearings something that I can replace? This machine is in our engineering building which has a fantastic shop. I wouldn’t be afraid to do it unless it required special tools that we don’t have. The diagram (which is just a simple diagram, not a service manual) shows the bearings at the base of the spindle by the chuck, exactly where the sounds coming from. It also gives a company and part number for the bearings.

Anyone have any experiences with this machine or changing spindle bearings in general?

[RICHARD ZASTROW]

OC, You might want to look up " NC bearings again " by viper 6383 at the General Mechanical / Engineering forum. The local bearing guru "NC cams" provides much knowledge and experience based information.

[NC Cams]

As DZASTR suggested, (re)check the prior post(s) as this topic has been thoroughly discussed before in at least 2, perhaps 3 threads for several Bridgeport and/or VMC spindle bearings.

Replacing the bearings is one thing, who will/can grind the ID of the spindle after you reassemble the thing to put the tool register back being concentric with the C/L of the new bearings.

BTW, if all you have is a generic bearing number (7204, 6206, etc) this is NOT the part number of the exact replacment bearing. The FULL bearing details are spec'd out by the alphabet soup that comes AFTER the bearing size and is noted by codes in the ( )'s in the generic bearing size numbers as following examples: 6206( ) or 7204( )