You didn't indicate which OEM bearing numbers you replaced buy I'll make some assumptions to help you get going.
If the lower bearings are the OEM #11190238 the EXACT Fafnir OEM equivalents to the Bridgeport pieces are/were JM207PRDB FA52727 - anything and I do mean ANYTHING else is NOT an exact equivalent.
These SHOULD come with OD/ID high point markings AND over/undersize marking of the ID's and OD's in 0.0001" increments so as to enable you to selectively fit them to the housing or shafts. They are a special combination ABEC3/ABEC 7 hybrid bearing that Bridgeport conjured up way back when.
IF the "worlds finest" bearings don't have these special qualifiers as well as a special preload and some other special internal features,you got a generic part that is NOT of an OEM equivalency - I know of what I speak since I have the OEM print for these very bearings sitting in front of me as I type this reply.
There are some other specs involved qith these gems but nothing that I'd care to publish since a user couldn't do anything about meeting or getting them if they had to/wanted to.
If you want a high performance bearing "upgrade", you could try the 7207CTYDUMPA7 or 7207CTYDUMP4 true machine tool grade bearings from NSK. These are FULL ABEC 7 and have touch more preload than the OEM spec but nothing signifigant. You'd never know the difference when they are properly installed except that they should turn smooth as glass and have no appreciable runout.
NOTE: The NSK's do not have the shield/seals that the Bridgeport bearings used but that shouldn't be an issue as the housing is sealed up pretty well and the seals on the bearings are not mandatory if that is the case. If you use these, you MUST check and grind the 12193513 spacers to be exactly the same axial length - some spacers may be unequal length to tweak preload. Grease lube the bearings with a 25% fill of "Andok C" (Chevron makes it I think) bearing grease (the exact OEM grease) and you'll should be good to go.
In either case, once you install the bearings, the spindle ID's will need to be ground to bring the axis of the spindle back to being concentric with the axis of the bearings. Having been at Hardinge a number of years ago and seen the process, this is EXACTLY what they do when they service and/or build/rebuild a Bridgeport mill spindle.
Where you'll find a reputabe shop to do this is probably your hardest find, especially in light of your experiences to date.
Rough turning "new" bearings were probably either damaged at/during installation and/or were lubed with contaminated grease. Running in rough bearings hoping that it "heals itself" is worse than wishful thinking - I'd contend that it is just plain dumb.
The 11190237 upper bearing is EXACTLY a M206K Fafnir. Again, anything but is a generic "equivalent". I'm pretty sure, but from memory, that the M suffix of the Fafnir means that the bearing is specially qualifed to at least ABEC 3/ ISO P6 for machine tool use - it may have other special specs, special lube and/or other non-standard, non-published features but I don't have the OEM bearing print to confirm that. Again, anyting BUT is NOT the exact equivalent.
Re: bearing installation. You can press the old ones off/out but NEVER, EVER use force (hammers, presses, pullers, etc) to install the new ones. If you Freeze the spindle and heat the bearings, they should literally drop together. When the temp normalizes, the parts should remain tight. If the bearings are loose when temp normalized, congratulations, you have a funky sized housing/shaft and need the selective sized bearings that were originally used that you'll probably never find anymore.
The alternative: chrome and rr-grind the shaft to standard size to obtain proper fit.
It is NOT that hard to replace spindle bearings without damaging them if you take time and do it properly. The trouble is, some guys want to rush or slam stuff together. In other instances, familiarity breeds contempt and or sloppy procedures. You seem to have been a victim of one of these methods - I'll bet you can figure out which by now.
You might give Brian at BPT Machines a call. He was a true factory technician and knows of several "old timers" who originally built the Bridgeport spindles before Bridgeport went belly up and still service them. Perhaps he can put you in touch with someone who can straighten out what you have. Call him at 630-984-9942
Good luck  |