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  • Spindle repair

    Hi!

    Got my mill's spindle parts back from re-grinding a week ago. Had to wait for the grease I forgot to order in time. Got that two days ago. 400 g just 70 €. OMG!
    Yesterday, I preassembled it and let it sit over the night for the temperatures to equal out. The shaft was in the freezer, the bearing in the oven and the quill's house at room temperature.

    Temperature difference between shaft and bearing was 90°C, so it slipped over with no force at all, all the way down.

    Here's a picture how I measured the axial play. 5 µm was the call. Indicator is a Mahr with 0.5 µm per division. The hammer was needed to set the bearing against the nut. By just adjusting with the nut, the bearing jumped about 1/100 mm and then the play was out of specs again:


    Yes, that puppy is about 450 mm long! Has an type 40 cone.

    The taper was quite abused, so I asked to remove as little as possible and leave some spots unground. Otherwise, the hydraulic clamp would shift too much:


    As the mill has two absolutely identical spindles (horizontal and vertical) but I only got one new pair of tapered roller bearings, I had to rescue one pair of bearings. The second not-so-good-spindle will be the horizontal one. Two bearings (out of the 4) were ruined. One had a severe pitting in a single spot of a single roller. The other one started microscopic pitting at all cones.
    Here is one of the good ones disassembled and after cleaning:


    As this bearing has no outer ring, the rollers directly roll in the quill's housing. Due to the pitting that ocured, that race way had to be reground too.

    The second spindle is out for re-grinding and will be assembled with the spare parts.
    I was told, that a new spindle costs 10000 €. Clearly NOT an option!

    Will let run it through the RPM and temperature cycles today and enjoy a like-new-spindle with a beer or two.


    Nick

  • #2
    Nick what mill has a quill with no outer bearing race?I want to know so I can avoid buying one
    I just need one more tool,just one!

    Comment


    • #3
      Nick what mill has a quill with no outer bearing race?I want to know so I can avoid buying one
      The bearing itself has no outer ring. Instead, it runs directly on the quill's tapered bore. They wanted to make it slim I think.
      I have no picture, but if I don't forget it, I can make one as soon as the second spindle comes back from grinding.
      After 4000 hours, it needs a service. Disassemble, clean, regrease and adjustment.
      The tapered rollers are bored and you have to put the grease in there. Works as a reservoir.


      Nick

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      • #4
        Nick, I take it you made note as to any markings on the bearing races as opposed to markings on the spindle for proper run out.
        A race ground into the spindle scares me also.........

        JL.................

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        • #5
          Nick, I take it you made note as to any markings on the bearing races as opposed to markings on the spindle for proper run out.
          No. The inner ring has no high spot marking. The shaft was reground with a steady rest running on the bearing's seat (bearing removed). So the shaft should have zero runout. Only runout remaining is from the bearing, a "Garmet High Precision".

          A race ground into the spindle scares me also.........
          That's for better earings through service.
          Disregarding for that, it is OK. But even more expensive.


          Nick

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          • #6
            That reground spindle end looks great! Are you sure there isn't a race hidden in the quill? It may look like one piece but is really a pressed in race.
            Andy

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            • #7
              Originally posted by vpt
              That reground spindle end looks great! Are you sure there isn't a race hidden in the quill? It may look like one piece but is really a pressed in race.
              If there were a (hidden race) I think there would be some kind of dead giv away such as a slight difference in the color of the steel or an inner edge with a slight radius or break, markings on the edge of the race, etc. I've run across stuff like that in the past.

              JL................

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              • #8
                Nick, just wondering........... are you mixing and matching rollers from other bearings????????? That could lead to premature wear.
                I never heard of that brand bearing.......... it resembles a Timkin roller bearing which my Clausing 5900 uses for the spindle, but they have outer races.

                JL....................

                Comment


                • #9
                  Originally posted by JoeLee
                  I never heard of that brand bearing.......... it resembles a Timkin roller bearing which my Clausing 5900 uses for the spindle, but they have outer races.
                  Gamet is a proprietary English tapered roller bearing. Their schtick is hollow rollers. They're now made to order, and thousands of dollars/set.

                  But the Gamet bearings I've seen have cups and cones, just like a conventional tapered roller bearing.
                  "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                  Comment


                  • #10
                    Originally posted by MuellerNick

                    The taper was quite abused,



                    Boy I'll say ---- do you own any tool holders without drive flanges?
                    It's like something spun in that dawg....

                    Comment


                    • #11
                      Looking at the damage that was too deep to clean up, I think your lucky it came out as well as it did. Too much removal on a taper could result in the mating piece seating too far in. I've seen it before in Bridgeport R8's.

                      JL...........................

                      Comment


                      • #12
                        Boy I'll say ---- do you own any tool holders without drive flanges?
                        That wasn't me. I removed the stones for assembly. They shure will come back in.
                        It looks like someone "repaired" it with a die-grinder. Freehand! You can see an extra cone right at the end that doesn't belong there. At the very end, directly at the face, there is a chamfer the grinder made. Just maybe 2mm wide to remove the sharp corner.
                        Also, the cone's seat is split. Means the middle has a recess. You see that at the lower end of the reground surface.

                        On one spindle, I had a runout of 0.02 mm, on the other 0.025 mm.

                        Nick, just wondering........... are you mixing and matching rollers from other bearings????????? That could lead to premature wear.
                        No. Rollers and inner ring are NOT mixed. The outer ring doesn't exist. All bearings were disassembled, cleaned and re-assembled separately. So no chance to mix any parts.

                        Also, if just one single roller had a pitting, the ring is ruined. -> bin! There is no use in trying to rescue it.

                        If you have doubts about recycling the used but good (or undamaged) bearings, you are right. But they will go into the horizontal spindle that I will use very seldom.

                        could result in the mating piece seating too far in.
                        Right. So that's what I asked for. He also faced it off to get the right distance back. I'm very happy with what he did.
                        I'm also happy that it was too big for my cylindrical grinder. I'm not at all as good as the one who made it.
                        It took him 5 hours. Most of that was setting things up (as always).

                        Edit:
                        I also got the original drawing, so he/we knew how deep the hardness went. He didn't have to grind through the hard layer.


                        Nick
                        Last edited by MuellerNick; 11-27-2010, 11:42 AM.

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                        • #13
                          Nick, what machine is this from? Have you posted pictures of it before?
                          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                          • #14
                            It is a MAHO type MH 700 C.
                            I doubt I have posted pictures, and I don't have good ones at hand.
                            I bought that mill almost two years ago with a broken CNC. I replaced that with EMC2 and a bunch of custom-made boards. The control is running and works, but it ain't finished. That conversion took me longer than I imagined in my worst nightmares.

                            The mill was built '82. Weights something like 3.3 tons, has 700 mm in X, 500 mm in Y and 450 mm in Z. The DC(!) motor for the spindle has 8 kW. The biggest servo for Z weights 84 kg.
                            Spindle RPM is 20 .. 3100 with 4 gears. But I think I'll change the max speed to 4000 RPM when I see that it is running nice and doesn't get too hot.


                            Nick

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                            • #15
                              Can't complain!
                              Spindle run in. Temperature at 2000 RPM is 35 °C. Maximum allowed would be 50 °C. Gonna remove the whole spindle again tomorrow and add the hydraulics and recheck the play.
                              Runout is 2..3 µm. Not to shabby.

                              But now, I do have a puzzle for you!
                              There is a seal in front of the lower bearing. It is contact-less, because a contact seal generates a lot of heat. One was ruined, so I cut it apart, because I don't know how it is made. That didn't help.

                              There is an inner and an outer ring. You can't disassemble them without cutting at least one ring. The outer ring seems to be out of aluminium, the inner ring is steel. They do have a little axial play to avoid contact. The play is maybe 0.3 mm. There is no seam whatsoever.

                              How are they made?
                              Al cast over the steel ring and then rolled to increase the Al rings diameter?

                              Prost!
                              Nick

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