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Lubricating a mill spindle? Oil? Grease? Seals?

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  • Lubricating a mill spindle? Oil? Grease? Seals?

    I'm working on an older Jet mill-drill, and had to replace the spindle bearings. I sprung for some hopefully-more-accurate P5 bearings, and got the spindle reassembled.

    However, I'm wondering how best to lube them, and keep them lubed. This mill is an almost direct copy of an old Clausing variable-speed drill press head, and I suspect they copied the quill with only minor changes as well- meaning I don't think they copied a proper milling machine style spindle bearing arrangement and it's attendant oiling needs.

    It's not a particularly fast machine, with an indicated top speed of a mere 1,400 RPM.

    I thought using oil would be preferable, but there's no real way to keep it on the bearings. The upper one is open to the hollow quill, and the lower one only has a rudimentary dust cover. No oil seal, not even a felt wiper.

    I assume I should just squirt some grease in there and call it good? Or is there a preferable method?

    Doc's Machine. (Probably not what you expect.)

  • #2
    I'd put a felt washer on top, an oil point to the felt, and some rudimentary cover on the bottom (but let it pass oil). Just a full loss oil system. Grease would be terrible (swarf and dirt attracting mess) with the bottom open like that. Don't worry about "keeping the oil on the bearings" - enough will stay there. Think of a typical BP type quill that's just a saturated felt washer and a few drops of oil per day of use.

    What does Jet recommend in their manual?
    Last edited by lakeside53; 01-10-2016, 09:17 PM.


    • #3
      I dunno, but factory applied grease comes
      from the deep fryers at the Asian food restaurant.



      • #4
        I once removed the spindle from my former H.F. Mill Drill. I had to repair the index pin on the side of the spindle into which the R8 collets and holders fit. The bearings were packed with grease when I disassembled it. I simply repacked it and it was still running fine 5 years later when I sold it.

        If you wanted to use oil I would install a felt washer to permit oil to seep through as mentioned by Lakeside53 above. You could also drill and tap the side of the housing to add an oil cup.

        My Webb mill has the typical three BP style oil cups. I put a few drops of light oil in those every week or so and the next day the spindle will be covered with oil. I've had the head apart to replace the worm cradle output gears for the power up/down feature and there are felt washers inside.

        Good luck.


        • #5
          Originally posted by lakeside53 View Post
          I'd put a felt washer on top, an oil point to the felt, and some rudimentary cover on the bottom (but let it pass oil).
          -There is a rudimentary cover on the bottom. I just used that picture to show the bearing layout.

          My problem with oil is that, with no way to keep it on the bearings (at least, on the upper bearing) and no (easy) way to keep a regular supply dripping in there, that the bearings will run dry(ish) over the course of a day. I'd rather not have to stand there with an oil gun giving it another pump every five minutes.

          A felt washer at the top isn't a bad idea, except there's no real room for it. The bearing is at the very top of the quill casting. A felt washer would be "slinging" oil out over the top edge of the quill.

          I can, I think, fit a thin lipped cover in there, which I'd like to do just to help keep gunk out of the lube. But it pretty much has to be attached to the spindle, which means it spins with the spindle. Which of course means any oil or grease on it gets spun out too.

          Grease would be terrible (swarf and dirt attracting mess) with the bottom open like that.
          -Yes, it would be a mess, if the bottom were indeed open like that.

          It does have a screw-in cover, a thin plate that has nothing but three unevenly-spaced drilled divots in it, so that you can apparently just use a small hammer and a drift punch to screw it in or out.

          I'm thinking about making a new cover, and could, theoretically, incorporate a seal, either a true lip seal, an O-ring or just a felt washer. (The current cover doesn't have room for any of that.)

          The new cover could also have an actual grease zerk. Probably not entirely necessary, but possible. (The cover doesn't rotate with the spindle.)

          Don't worry about "keeping the oil on the bearings" - enough will stay there.
          -Unfortunately, no, it doesn't. I had the M/D turning briefly the other day, as I was testing some of the new parts, and for lack of a better option, I just threw some spindle oil on the bearings. They're not fully seated yet, and I wasn't doing any cutting, but I wanted some oil on there so I didn't hurt my $300 bearings as I was running it up.

          Virtually all of it dripped back out within a couple of hours. Besides the loss of oil on the bearings themselves, there'd be a constant fling of oil as the machine's running and I get enough gunk on me in a day as it is.

          Think of a typical BP type quill that's just a saturated felt washer and a few drops of oil per day of use.
          -This is kind of why I asked. I've never been inside a Bridgeport mill, or really, any other quill-type vertical mill, and don't know how they apply or control the oil. My Bridgeport-clone Grizzly has an oil cup for the spindle, but I never see it dripping down off the spindle nose itself. My Arboga drill press, which has a similiar quill to this mill-drill, just has a dust cover. Those bearings I greased.

          What does Jet recommend in their manual?
          -I have no idea. I didn't get a manual with the machine, although I did discover, by blind luck, that the Ozark Woodworker had a copy of the manual, so that should be here in a week or so.

          I don't expect it to be terribly detailed on service and maintenance though. This is a (probably) 80's vintage Taiwanese import, so I suspect the manual consists of little more than some bad line drawings, some likely-inaccurate exploded views, and a parts list whose part numbers don't correlate with any known belt or bearing number in existence.

          Doc's Machine. (Probably not what you expect.)


          • #6
            I can't remember where I saw it (Hobby Machinist I think) but someone made a clear plastic cup to go over the end of their spindle to catch the oil and just emptied it when it got too full. Add a thick enough piece of felt and it should draw some up too. Doesn't address the top bearing though.

            Sounds like grease is a better option in this case, especially if the bottom can be sealed. I've also seen pics of these mill drills without any lower bearing cover, usually in "this is how I replaced my bearings" type threads.


            • #7
              The BP type mill spindle gets a few drops a week. No continuous oiling at all on the Abec 7 bearings - just a light film.


              • #8
                The last set of bearings that I bought had a spec that showed different RPM depending on whether dry, oiled or greased. Will that make a difference for you?

                At the end of the project, there is a profound difference between spare parts and extra parts.


                • #9
                  I'd have to say grease, a lip seal, and a shield. 1400 rpm should be well within the capabilities of grease, and so it would probably be recommended. Having said that however, my spindle bearings have oil cups above them, and they do have some kind of lip seal.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


                  • #10
                    If you use oil, be prepared for a never ending mess everywhere. A high melting point lithium grease would be preferred, you don't need much, and it won't migrate very fast. The drill-mill that I rebuilt had no proper bottom seal, so I found a large, fat o-ring which just rotates on the spindle and rubs on the end of the quill, it keeps the muck out of the lower bearing.


                    • #11
                      Hello Doc,
                      I have a Benchmaster mill and originally it only had felt 'seals'. The tapered roller bearings are intended to be packed
                      with grease like a wheel spindle. I have replaced the felt seals (which aren't available anymore) with standard lip seals
                      and packed the bearings with high quality wheel bearing grease. Other Benchmaster owners do the same and everyone
                      seems happy and report no issues. While there are no grease nipples on the spindle housing, everyone seems to get
                      many years from a re-pack.

                      I'd go with that approach on your machine.

                      1973 SB 10K .
                      BenchMaster mill.


                      • #12
                        My Bridgeport style heads have class 7 bearings with a labrynth seal in the bottom nut that screws into the bottom of the spindle. The bottom bearings (2 angular contact ball bearings) are lubed with Kluber NBU-15 grease. I would recommend this to anyone with a mill spindle. It stays in the bearings without any problems. The top bearing is a plain radial with seals. It has Kluber grease too. These spindles will run for long periods of time at 3200 RPM and not get above body temp. They feel slightly cool to the touch. With other common bearing grease at this RPM they would get hot enough to burn your hand in a couple of minutes.


                        • #13
                          Please elaborate on this Kluber grease. I'm interested in learning about that stuff!

                          1973 SB 10K .
                          BenchMaster mill.


                          • #14
                            It's from Germany. Google Kluber Lubrication.


                            • #15
                              The mention of Kluber grease brings back memories of the fitters at my old firm coming into our shop to weigh Kluber grease to the nearest gramme to pack into spindles for the tooling for transfer machines used by the motor manufacturers. The spindles were packed for life, a very long life, as the machines ran 24/7 and only had a rest during the annual shutdown. The strict quantity was because the spindles were sealed and overfilling would drastically shorten the life of the bearings. I have no idea which grade would be best, it is very expensive so get a small amount.