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DIY bearings in 5hp motor idler RPC

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  • #31
    the bolts all pass outside the center frame, so clocking is a non issue.
    some pics of what I got, with the bearings pulled off the shaft, there is corrosion on the inner side that I could not see before.
    you can see both sides bearings are sealed, and the grease zerk on the end bell

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    • #32
      Maybe that corrosion is what was making the noise? I bet it was. Probably from the temperature changes, got some condensation in there over the years.


      • #33
        Originally posted by nickel-city-fab View Post
        Maybe that corrosion is what was making the noise? I bet it was. Probably from the temperature changes, got some condensation in there over the years.
        as I mentioned earlier, I believe this motor got half submerged at some point in its life. when I was tightening the bearing puller, i did see some movement in the bearing that looked awful


        • #34
          Originally posted by Ringo View Post

          as I mentioned earlier, I believe this motor got half submerged at some point in its life. when I was tightening the bearing puller, i did see some movement in the bearing that looked awful
          Oh, OK I didn't remember that part. Gotta admit I would change the bearings for sure if it was submerged. Figure its cheap insurance. There really isn't much else to go wrong in a motor except burning out the windings, far as I know.


          • #35
            tomorrow is shopping day for new bearings.
            then, to figure out how to press them on. I do not have a arbor press, hydraulic press frame, none of that.
            hammer and piece of pipe,,,??
            I gotta invent something....
            So, how far can you heat the sealed new bearings before you cook out the lube?
            Last edited by Ringo; 07-29-2020, 10:50 PM.


            • #36
              One shop I was at back in the day, had an old electric fry pan full of oil. They would turn the knob to boiling and soak the bearings in boiling oil. Then they bearings would just slide right on -- but you had to work quick.

              I always used a chunk of pipe against the inner race, with no probs.


              • #37
                a chunk of pipe might be my easiest for a 1-off item
                maybe 2-off because both ends different size


                • #38
                  Piece of pipe works. I prefer black iron pipe, no plating to flake off into the bearing. Not an issue if sealed, though.

                  Originally posted by nickel-city-fab View Post
                  One shop I was at back in the day, had an old electric fry pan full of oil. They would turn the knob to boiling and soak the bearings in boiling oil. Then they bearings would just slide right on -- but you had to work quick.

                  I always used a chunk of pipe against the inner race, with no probs.
                  Some bearings start to lose hardness not far over boiling water temp. Boiling oil should knock them back a bit in hardness, that's over 400F.

                  Keep eye on ball.
                  Hashim Khan


                  • #39
                    I been wondering about dunking the shaft in a bath of dry ice & alcohol


                    • #40
                      Originally posted by Ringo View Post
                      So, how far can you heat the sealed new bearings before you cook out the lube?
                      its all the in bearing company catalogues/literature. around 260-275F irrc.
                      in Toronto Ontario - where are you?


                      • #41
                        Boy, you guys like to argue. Let's just say it's personal preference as to whether you mark the bells so you can put them back on the same way later. If you put them on just like they came off, you can't be any worse off than when you started. Conservative, sure, but what the heck, it takes what ten seconds?

                        I have rebuilt a few dozen 3 phase motors. I wrote up my procedure once. It could have used some editing, but it's still helpful. I have appended it below as plain text. You can tell I'm a home shop guy and not a pro, but the information in here is as good as I could find.


                        How To Rebuild A Three-Phase Squirrel Cage Motor

                        I'm talking here about rebuilding motors of the size you will see most often
                        in a home shop, motors between 1 and 7½ hp. These motors are getting more
                        expensive around the Seattle area especially with the closing of Boeing
                        Surplus, so the ability to rebuild them is becoming more important.

                        It is a fair amount of work to rebuild a motor, so prudence would dictate that
                        you should start with a motor that still works. I have a phase converter in my
                        shop which has receptacles built in, and I made up a little cable with large
                        insulated alligator clips on the free end, which plugs into my phase converter
                        via a disconnect box. That way I can clip the alligator clips onto my motor's
                        wiring quickly and throw the switch on the disconnect box to spin up the motor.
                        Most of the time this setup just gets in the way, but it is very helpful when
                        working on 3-phase motors. Start with a motor that works! If yours does not work
                        (and I've run across some that don't) check continuity in the wiring and check
                        the connectivity of the wiring. There is often a wiring chart on the nameplate
                        or printed on a label inside the motor's wiring box.

                        MOTOR BEARINGS

                        Look at the nameplate. Many motors' nameplates call out the motor bearing
                        numbers. If yours does not, don't worry, just don't throw away the bearings
                        until you read their numbers. Once you have the bearing numbers, order new
                        bearings. Try to get good bearings if you want a quiet motor. Bearings should be
                        electric motor rated. Some bearings have an EM in the part number which stands
                        for "electric motor".

                        A note on bearings. Bearings come open, shielded, or sealed, on one side or on
                        both sides. Shielded bearings don't have anything that bears on the inner race
                        to restrict its rotary motion. Most sealed bearings do. If you dig down into
                        your bearing manufacturer's datasheets you will learn their nomenclature and you
                        can look up whether their sealed bearings are contact seals or non-contacting
                        seals. The latter are rare but work very well indeed on electric motors because
                        contact seals do bear on the inner race so some of the motor's energy must go to
                        overcoming that resistance, and thus the bearings will heat up more and probably
                        have somewhat shorter lives as a result. On the other hand, contact seals
                        probably keep out dirt and contaminants the best, so like many things it's a

                        I don't recommend buying cheap no-name import bearings even though it is
                        tempting because of the price. I have rebuilt motors using cheap bearings and
                        have been dissatisfied with the noise levels that resulted. When I first
                        switched to top quality bearings I was amazed at the difference. I have had good
                        luck finding bearings on ebay even though that site isn't at all what it used to
                        be. Order the bearings as early as you can in the process. Some quality bearing
                        manufacturers you can look for include Fafnir, SKF, FAG, Toyo, Koyo, NSK, NTN,
                        Nachi or NHBB.


                        If your motor is pretty clean and has an intact coat of paint, you won't need to
                        strip and repaint it. Mine never seem to be -- I nearly always wind up
                        repainting the motors I rebuild! Now is the time to decide on the color and get
                        the paint purchased or ordered BEFORE you need it!


                        Clean off a few square feet on the bench. I like to lay out a clean towel. You
                        will need a soft-faced hammer and a pressurized air hose with a blowgun fitted,
                        plus a few other hand tools for this job.

                        Put the motor on the bench. Remove anything attached to the shaft, like a pulley
                        or a key. Before you proceed, look at the motor well or take a digital picture
                        of it. This is to remember which end the shaft comes out, and which way the
                        motor's junction box is oriented. While you're at it, take a small hammer and a
                        small sharp chisel and make some witness marks across the end bell cracks in an
                        area that won't show, so you can't possibly have any question of the orientation
                        of the end caps during reassembly. I like to make two cuts forming a V. One V
                        for each end bell. Make one V narrow and the other wider and you'll never get
                        the end bells mixed up.

                        If the motor is totally enclosed fan cooled (TEFC) remove the air shrouding
                        screws and the shrouding, retaining the screws and remembering which ones they
                        are. Now you have exposed the fan blade, which is often plastic, and which can
                        be difficult to get off intact. It must be done, however, so loosen the clamp
                        bolt carefully and do what you can to pry it open. Slip steel flat bars behind
                        it as close to the central shaft as possible, and using as little force as
                        possible, try to lever the fan blade off a little at a time. At any rate, remove
                        the fan blade, hopefully without hurting it. Replacement TEFC fan blades may be
                        available from the manufacturer if they are still in business and your motor is
                        still supported for parts. If you intend to use the TEFC motor in conjunction
                        with a VFD (a common arrangement these days) you may well be permanently
                        removing this fan blade and replacing it with a muffin fan fitted to the
                        shrouding, one which will deliver a constant air flow no matter how the variable
                        frequency drive changes the power frequency. In that case, keeping the TEFC
                        cooling fan intact isn't as important, although I try to save them anyway.

                        All motors seem to have 4 long skinny bolts with regular hex nuts holding the
                        motor end caps on. If you see any corrosion or paint on the threads around the
                        nut end, apply quality penetrating oil. (I like Kroil but I use others, just
                        don't use WD-40.) Remove the 4 bolts entirely. Now take a soft-faced hammer and
                        give the end of the shaft a good whack. The rear end cap (away from the shaft)
                        should pop right out. Once the cap is loose from the motor shell, pull the cap
                        off the motor's rotor. The next step is very important! Look in the end cap's
                        bearing boss on the inside. You should see a wavy washer in a pile of old
                        grease. Remove and save the wavy washer. If it isn't on that end it is probably
                        on the other end. At any rate, remember which end it came from.

                        Then hold the rotor shaft roughly in a central position and give the exposed
                        shaft end (not the motor's drive shaft, this is the shaft end you just removed
                        the end cap from) a whack with the soft hammer to pop loose the front end cap
                        out of the motor shell. Now remove the end cap with rotor and put them down
                        carefully on a clean place. Remove the end cap from the rotor, which should not
                        require much force. The bearings should stay on the rotor shafts when you remove
                        their respective end caps. Again, check for wavy washers.

                        Now the end caps can be completely cleaned. They may have zerk fittings leading
                        to grease passages which lead down to the bearing cavities. If so, remove and
                        retain the zerk fittings and use compressed air to blow the grease out of the
                        grease passages from the inside out, aiming the flying grease glob cleverly into
                        a garbage can. The reason I say to do it from the inside out is that otherwise
                        it splatters on the inside and sometimes goes all over your shirt and maybe into
                        your face. Clean out the inside of the end bells with carburetor cleaner and
                        compressed air and small wire brushes and 3M pads as necessary. The outside
                        cleaning treatment will vary with what kind of metal they are made of. If
                        they're made of steel or cast iron they can be boiled in water with a few
                        tablespoons of Cascade dishwashing powder added. Bring to a simmer and boil long
                        enough to remove or completely loosen the paint and all grease. Carry the whole
                        pan to a utility sink and rinse the parts under hot water, scrubbing on them
                        with a stiff brush or even some steel wool. Work quickly as you want the parts
                        to stay hot enough to self-dry within 60 seconds. NOTE - you can not use a hot
                        caustic bath like the above on aluminum or zinc-based end caps, they will get
                        pinholes in just a few minutes since the bath eats those metals!

                        After the end caps have been degreased they can go into a derusting bath. You
                        can simply dunk them into a vat of Evapo-Rust with a naked light bulb nearby to
                        warm the bath a little, or you can set them up for electrolytic derusting, or
                        you can blast them using glass beads or other media. If the end caps are made of
                        aluminum or zinc then you may be able to simply rub the rust away with a 3M pad.
                        But get any rust completely removed. At this point the end caps are ready for
                        repainting. The final step I do to the end bells is to locate your witness
                        marks, which hopefully are still visible, and take a sharpie and make a mark on
                        the inside of the end bell so you can quickly look at the inside to see roughly
                        where your witness marks are, as they can be tough to spot once you repaint. If
                        your end bells are made of steel or cast iron and you are going to paint the
                        inside, then wait to mark with your Sharpie until after painting.


                        • #42
                          (rest of above text)

                          Moving to the main motor body, you will see a shell, an electrical wiring box,
                          and inside, windings. This part of the motor is called the stator. Start by
                          blowing out the stator and looking inside carefully for any insect nests or rust
                          damage. Be careful around the windings! Don't do anything rash like stick a
                          whirling cup wire brush down in there! One faint touch to the end of the wirings
                          and you might dislodge a lamination which means your motor will buzz horribly,
                          so go gently!

                          Completely remove and disassemble the motor wiring box, carefully retaining the

                          Now look all over at the stator. Is it very rusty? If so, dunk the whole thing
                          into Evapo-Rust overnight. It won't touch the winding varnish or the nameplate
                          coloring, and it certainly won't dissolve the nameplate metal, but it will
                          remove or greatly loosen the rust, particularly if the bath is warmed to 70 or
                          80 degrees F. When it comes out, rinse it with hot water and bake it in the oven
                          at 170F for half an hour or so to drive out any remaining moisture. This
                          treatment works better if you take the part out after an hour or two in the
                          Evapo-Rust and scrub or scratch on the rusty areas, which will greatly help in
                          letting the Evapo-Rust solution penetrate into the rust and dissolve it. I have
                          had amazing luck with this method.

                          Now use the exact same method on the motor's rotor. First remove the bearings. I
                          suggest buying a cheap bearing puller set from Harbor Freight. If you need to,
                          or if you're curious, clean the bearings once you get them off, and look at
                          their numbers. Derust the rotor if needed, and polish the shafts afterwards. I
                          keep a 3M deburring wheel in a bench grinder for polishing of this type - it
                          works very well. Once the rotor is clean and its shafts are polished until
                          shiny, with no nasty nicks or dents, if you like you can take it to a balancing
                          shop and get it precision balanced. This will cost $100-200 but then the motor
                          will run amazingly smoothly. It normally isn't necessary.

                          Clean and derust the external fan shrouding if necessary, as well as the motor's
                          electrical wiring box and its lid. If there is a label inside the wiring box,
                          try to remove it and glue it back in after cleaning, or clean around it, or make
                          a replacement label with the same information. Also derust any of the fasteners
                          you can't or don't want to replace. Any fasteners you derust chemically should
                          be dried carefully and oiled or they will rust very quickly. If the wiring box
                          is not steel or cast iron use carb cleaner or brake cleaner to degrease it. I
                          have heard that a mild acid like vinegar will remove white powdery buildup on
                          pot metal parts, but I haven't done this so if you try it then watch it
                          carefully to make sure it isn't eating the zinc itself.

                          Once the stator is completely clean, look very carefully at the wiring which
                          pulls through into the wiring box. See if the insulation is cracking. If it is,
                          get some shrink-wrap tubing of the appropriate size and shrink-wrap one wire at
                          a time, making new labels with a labelmaker. Don't screw up the labels! Be kind
                          to your wires - handle them with care, but do whatever you need to to make sure
                          their insulation will last a long time as well as their label.

                          Now you have completed the motor's disassembly, and it is time to repaint.

                          PAINTING AND RELATED PREP WORK

                          I'm not a great painter, probably not even a good one. I don't know how to
                          paint using compressed air. But I have painted a few dozen shop projects
                          and they all seemed to turn out OK, and I've learned a few things along the way.
                          Of course it is very important to have the parts clean and degreased. It is also
                          important to disassemble things and to set up your painting area so you don't
                          get paint all over your bench, for example. I cut up little squares of paper (an
                          office-type paper cutter works way quicker than scissors for this) and roll the
                          paper up into little tubes and put them into holes and let them unroll until
                          they mask the bores nearly completely. I started out brush painting shop
                          projects, and I have learned a couple tricks. Use top quality brushes, thin your
                          paint a little if it has been sitting for a few years, get a paint mixing
                          propeller on a stick thingy at the hardware store so you can use a drill to mix
                          the paint. If it isn't warm out, put a little Japan drier in your paint, this
                          will help it dry quicker. Having come up in shipyard work, I have learned the
                          value of good quality primer. I often will prime areas of projects that don't
                          show and which I've derusted, but I don't want to take the time to make perfect
                          looking. As for spray cans, I have long had a dread of trying to use cans that
                          aren't brand new from the store because often they plug about a second after you
                          start and then nothing I've tried will work to free them up. I think that
                          sediment slowly sinks to the bottom of the cans, and the regular 1-2 minutes of
                          haphazard rattle shaking doesn't mix them up enough, so that pile of goo is
                          sitting there just waiting to clog up the tube. Someday I'm going to build a
                          spraycan shaker - how hard can it be? Anyway, shake the can(s) until you can't
                          stand it anymore, and then follow the directions. Might help to store spraypaint
                          cans upside down too, don't know. I like to put big plastic bins over just-
                          painted items and stick a trouble light with a low wattage bulb inside the bin.
                          This warms the parts and the paint dries much more quickly. Motor parts often
                          will fit into your oven, and you can warm them to 175F or so to dry the paint

                          Spend some time to mask the motor's nameplate carefully. I generally cover 100%
                          with masking tape and then carefully trim the edges using a box knife. Splashing
                          paint all over the nameplate is amateurish and a sign of sloppy workmanship, and
                          it is to be avoided at all costs.

                          After the motor parts have been painted, remove all masking. Some masking tape
                          adhesives can harden, so don't leave the masking tape on any longer than you
                          need to, or buy quality masking tape in the first place.


                          The first step is to clean out the bearing recesses on the end caps. Use a
                          solvent and get all of the old hardened grease out. This step is very important.
                          Next, lightly grease the wavy washer and the bearing cavities. The bearing on
                          the end with the wavy washer is supposed to be able to move as the rotor heats
                          up or cools down. Greasing the area really helps with that, and also with

                          Motor bearings come prelubricated. I try to buy electric motor rated shielded
                          bearings. But sometimes I have to use sealed bearings, which have more rolling
                          resistance and thus rob you of power and get hot. If the bearings are open, then
                          grease them.

                          The rule of thumb on installing motor bearings is that bearings smaller in
                          diameter than 2" don't need to be heated for installation.
                          Press bearings smaller than 2" onto the motor shaft, making sure to only press
                          on the inner bearing race. Push as evenly as possible. If only one side is
                          shielded, put the open side towards the shaft ends, not towards the center of
                          the motor. The bearings should be a light press fit onto the shaft and a tight
                          slip fit in the end caps. If you find you need a shop press to push the bearings
                          on you are doing something wrong.


                          • #43
                            (last bit)

                            Sealed bearings (with rubber visible on the sides) larger than 2" should be
                            heated to around 190-200°F. Shielded or open bearings (all metal) can be heated
                            to 230°F. You can heat a bearing by setting the bearing on an incandescent light
                            bulb. Wear a welding glove when handling hot bearings. Never use a torch to
                            preheat a bearing. Under no circumstance should bearings ever be heated to more
                            than 250°F. Anyway, heated bearings should slip right onto the shaft and seat

                            If the end caps are loose on the bearings, or if the motor knocks after
                            reassembly, don't try to glue the bearing in place using a Loctite product,
                            because then the bearing won't be able to move to accommodate heat expansion of
                            the rotor shaft. Rather, take a trick from the small engine rebuilding guys and
                            use a prick punch to make several punch marks in the bearing boss of each loose
                            end cap. A ring of maybe six center punchmarks around the bearing boss midpoint
                            will make the bearing a lot tighter. If you had one, you could also use a hand
                            inside knurling tool. I have heard that a lot of very expensive Porsches have
                            driven out of the shop with bearings held in place by prick punches, and I have
                            done this to an electric motor - it works!

                            Once the bearings are solidly in place and the end caps' bearing housings are
                            lubricated with a little grease, now you can tap the end bells into place,
                            taking note of your witness marks so everything goes back the way it came off.
                            Now's when you will be glad you marked the inside of the end caps with a Sharpie
                            so you don't have to peer at the end caps with a magnifying glass under a strong
                            light to find your witness marks! Tap your end caps in place, and reinstall the
                            4 long bolts with their nuts, now all derusted and oiled. Tighten those nuts to
                            the proper torque which you can look up in Machinery's Handbook.

                            Reinstall the wiring box, using the original gasketing if available. Make sure
                            your wiring is all pulled through into the box, and put the lid on.

                            Take a final look at the zerk fittings. Are they rusty anywhere? If so, it
                            probably makes sense to replace them. They're inexpensive and are available at
                            any auto parts store or good hardware store. Reinstall the zerk fittings if the
                            motor was fitted with them. Now load up your grease gun with quality grease that
                            is compatible with the grease you used on the end cap bearing housings, and
                            force grease into the zerk fittings until you see it come out around the shafts.
                            Don't overdo this step, you don't want to jam too much grease in there, but the
                            idea is to make a plug of grease that will really help keep contaminants and
                            moisture out of the bearing area. Wipe away any grease that may have oozed out
                            around the shafts.

                            Now reinstall the TEFC fan and shrouding, if needed.

                            Look around -- there shouldn't be any parts left on your bench! At this point
                            spin up the motor to make sure everything's OK and running smoothly, and to
                            admire the sound of brand new motor bearings. If the motor spins up correctly,
                            you can congratulate yourself on a job well done!


                            • #44
                              what's a muffin fan fitted to the shrouding?
                              please explain


                              • #45
                                Originally posted by Ringo View Post
                                what's a muffin fan fitted to the shrouding?
                                Sorry it wasn't clear. A muffin fan is like the fans used inside a desktop PC. By "shrouding" I'm talking about the sheet metal that fits around the TEFC fan. Buy a fan that matches the motor voltage. If your motor uses 240 3-phase power, buy a 240 volt fan - it's simpler that way. Your VFD can probably control the fan so you don't need a separate fan power switch.

                                If you slow down a TEFC motor with a VFD, you also slow down its cooling fan. It may be prudent to replace that cooling fan with a separately powered fan which does not slow down as the motor's rpm is lowered. That way you will never lose cooling capability.