OK, back from dinner (homemade meat pie made from Christmas leftovers
![:)](https://madmodder.net/Smileys/default/side2side.gif)
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SO having convinced myself the spindle was OK back to re-assembly. Old bearings were dropped in some Jizer for a while to get them as clean as possible, meanwhile man from Royal Mail arrived with my RS Components delivery of an enclosure, 3 way switch and potentiometer to tidy up the 3 phase motor and VFD upgrade I am doing (more of that later
![:thumbup:](https://madmodder.net/Smileys/default/happy0034.gif)
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So the way the spindle bearings are mounted is they are situated in the casting and held on each side by a retaining plate/cover. This is bolted together with 4 bolts - but it became apparent that when these were machined they must have been done in situ or as matched pairs. Reason for saying this is on mine at least, they would only bolt up in one orientation, the bolts would bind as they went into the covers otherwise, so both sets were test assembled to find the "best" fit then centre punched to mark orientation (pic 2)
I then drove the bearing cups into the case so they butted up against where the retaining plate would sit and reassembled the shaft with dry bearings. I just did the front bearing first and was puzzled that as I tightened up the retaining plate on the front of the knee the bearing became tight to the point of stopping the shaft moving.
![:scratch:](https://madmodder.net/Smileys/default/icon_scratch.gif)
AT first I thought it was pulling in crooked and binding on the nose of the shaft so despite having aligned the plate/cover I tried all 4 possible orientations but still had the same problem.
Eventually I engaged brain and broke out the depth gauge. Now this is going to be hard to explain without a diagram - and your not getting one of those!!
![:bugeye:](https://madmodder.net/Smileys/default/confused0068.gif)
- but, it seems that if the bearing cup is driven in flush with the retaining plate (which sits inside the case) then when you tighten up the cover it effectively preloads the bearing to the point of clamping it. This is because the cover has a flange which will press on the bearing cage. To fix this I drove the cup in further so as to give me 1mm clearance between the cover and the bearing.
SO all tightened up nicely and shaft rotating freely. Repeated process on the rear and exactly the same problem! Again pushed the cup in a bot further and the bearing ran freely.
Moment of truth... wound in a small amount of preload (1/8th turn) and put the Dial Gauge on the nose and..... 0.015mm runout
Rebuilt the spindle again having lightly packed with the NGLI 3 bearing grease (Pic 3) equivalent of the original Centec recommended lubricant and then ran a series of tests at different pre loads as per Pic 4.
Result, finished spindle showing only 0.015mm runout at nose and when under load only deflecting 0.006mm (~3 tenths). Also end float is now zero. I then measured runout in the taper rather than on the nose (as suggested earlier) and it reduced to 0.01mm.
RESULT
![:ddb:](https://madmodder.net/Smileys/default/dancenana.gif)
SO bearings were OK (thanks Pete
![:headbang:](https://madmodder.net/Smileys/default/headbang.gif)
) - I can only think that somehow the cups had got moved around that that whilst I was winding in pre load on the shaft it wasn't actually loading the bearings hence why I was getting so much movement in my original test. Anyway, now I have done this I can move onto setting up for measuring and scraping ( a day(or 4 ) later than planned
![:doh:](https://madmodder.net/Smileys/default/doh-45.gif)
Cheers,
Paul.