bearings replacement - BT3000

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  • Bob0244
    Forum Newbie
    • Dec 2013
    • 13

    bearings replacement - BT3000

    Hi guys!
    My BT3000 conked out at the end of a project; the blade raising thread on the motor bracket completely stripped. I found and ordered a new bracket. Only saw the helicoil insert thread after the fact (I'm an old rookie). No matter. After stripping the motor assembly apart, I found 2 bearings in bad shape, and ordered both. One of the bearings on the arbor assembly was fairly easy to replace, but the other one seems impossible to get out. It's the one in the armature, between the plastic fan and the belt pulley. It just doesn't budge. I tried heating w/ a torch and almost burned the plastic fan, with no success.
    Do I have to remove the belt pulley from the shaft? How?
    Would appreciate some suggestions.
    Desperate Bob
  • LCHIEN
    Internet Fact Checker
    • Dec 2002
    • 20913
    • Katy, TX, USA.
    • BT3000 vintage 1999

    #2
    Pulley/bearing puller? Sometimes auto shops have ones for loan or rent. Or HF has them real cheap, too.


    Last edited by LCHIEN; 12-22-2013, 05:06 PM.
    Loring in Katy, TX USA
    If your only tool is a hammer, you tend to treat all problems as if they were nails.
    BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

    Comment

    • mpc
      Senior Member
      • Feb 2005
      • 979
      • Cypress, CA, USA.
      • BT3000 orig 13amp model

      #3
      Automotive machine shops, and many NAPA stores, have bearing puller & press equipment. For a few bucks they'll remove an old/bad bearing and properly press on a new bearing. Avoid the temptation to beat on the shaft with a hammer; that'll distort it. Steady pressure is the proper technique. A bearing puller uses steady pressure to remove bearings; a press applies pressure to the bearing and shaft to drive the parts together. As the prior post notes, only apply force to the part of the bearing that actually attaches to the shaft or into a cutout/bore; don't stress the bearing rollers during installation.

      Another technique to remove an old/damage bearing from a shaft: cut or split the side of it, turning it into a "C" shape. Often this is required when the bearing is mounted to a shaft that ends in a flange so there's no room to get behind the bearing with a puller. Another technique I've seen for bearings that can't be reached by a puller: clean the outer race and then weld "ears" to it that are wider than the flange or whatever part is preventing puller use... now the bearing can be straddled across a wide opening and the shaft pushed out of it.

      mpc

      Comment

      • Bob0244
        Forum Newbie
        • Dec 2013
        • 13

        #4
        Bearing OUT!!!

        Thanks for the replys guys!
        I do have a bearing puller. I used it to remove all the other bearings.
        Thanks to "I saw that!" I removed the belt pulley easily enough, knowing now that it is reverse thread and pulled the bearing out with no trouble at all.
        Joining this forum was the best thing I did for a long time. I learned how to replace and secure shims, replace pulleys, bearings and belts and I didn't even start checking other subjects.
        You guys are great!

        Comment

        • mmcmac
          Forum Newbie
          • Nov 2014
          • 53

          #5
          Originally posted by I saw that!
          ..when installing bearings on a shaft, only apply force to the inner race; when installing inside a bore, only apply force to the outer race. These rules also apply to removal of bearings that you'll reuse. Sometimes this isn't practicable -- e.g., I'd like to see someone install that rear BT3000 arbor bearing into the bracket with it on the arbor (or the arbor shaft into it after it's been installed in the bracket) while adhering to the above rules.
          I replaced all bearings in a bt3000 yesterday on both arbor and armature and as above was trying to puzzle out how to seat both assemblies in the motor bracket (#9) without axial loading of the bearings. I eventually resorted to heating the bearing mount seats with a heat gun on low power. It doesn't take much to expand the cylindrical seats such that the bearings just drop in, including the bearing pair at the rear of the arbor. I'd recommend cleaning out the casting seats to insure you're not fighting any debris as you don't have much time to work before the casting cools. Also seat the arbor before the motor armature such that you don't need to shield the plastic fan when heating the arbor seat. If the arbor alone has been removed for a bearing replacement, shielding the motor housing with a fully saturated wet rag when heating the arbor bearing seat should be sufficient.

          Comment

          • mmcmac
            Forum Newbie
            • Nov 2014
            • 53

            #6
            Originally posted by mmcmac
            I replaced all bearings in a bt3000 yesterday..

            Also at time of disassembly I didn't have a puller with sufficiently small fingers to grab the casting immediately at the bearing seats when pulling the arbor and armature out of the motor bracket. Pressing against the motor bracket housing periphery itself risks distortion of the casting particularly in the case of the motor bearing. I used a few 1/4" carriage bolts I had lying around and made press yokes from scraps of maple flooring. The head profile of the carriage bolts worked well given the limited clearance to grab the casting seat lips while a center bolt pushed against the shaft. The carriage bolts used here gave a relatively snug fit in 1/4" holes drilled in 3/4" maple. As such the bolt center-to-center distances called out resulted in an assembly tight enough to keep the carriage bolt heads from slipping off the bearing seat lips while under tension. Otherwise a tie wire can be wrapped around the bolt pair, drawing them together. Rotating the assembly such that the bolt heads extend under connecting casting web members is recommended.

            Also in retrospect I'll withdraw the suggestion to use a wooden block and hammer to free the guide holder from the motor assembly. After closer inspection of the locker bracket upper casting I'm quite concerned that portion of the casting could be distorted with too strong a blow. Using a wooden block press yoke and carriage bolts on the guide holder itself (similar to as described here) would be a far safer approach.
            Attached Files
            Last edited by mmcmac; 12-15-2014, 08:27 PM. Reason: clarity

            Comment

            • mmcmac
              Forum Newbie
              • Nov 2014
              • 53

              #7
              Originally posted by I saw that!
              I'm not a fan of heating bearings or bores. I know a lot of people do it and claim decades of success. Good for them.
              I'd avoid heating a lubricated bearing as well beyond its stated service temperature. But I suppose that is fair game as long as the temperature is kept low enough to avoid lubrication run out or breakdown. However in this case only the Al casting was heated sufficiently to develop the clearance. In retrospect I wish I'd tacked a thermocouple on the casting and measured the seat expansion to better gauge the temperature required. But it didn't take much and given both the coefficient of expansion and thermal conductivity of Al, I believe did not exceed what could be comfortably held in hand.

              Some even cook brand new bearings in an oven so the inner race will just slide right over the shaft with hardly any effort. They claim the grease suffers no adverse effects. Yeah, right. Somehow, I don't think the folks who designed the bearings and grease had this installation technique in mind when calculating the tolerances and lifespan of the products. Cooking these parts safely is not a notion I subscribe to.
              I didn't even consider heating a bearing vs. pressing onto its respective shaft. But after further thought might do so with a bit more research. The Mobil Polyrex EM2 lubrication in the RBI bearings I'd used has a stated upper service temperature of 175*C. Though I wouldn't be inclined to do so, I'd hazard even that could be exceeded for an installation operation. But I'd certainly contact RBI before attempting this to determine exactly what they deem acceptable.

              As for heating bores, I guess whatever works works, but I can't shake the idea that distortion is occurring which could cause trouble down the road.
              Taken to extreme that can be the case. But during manufacture Ryobi managed to seat the bearings in the casting somehow and I'd expect heating the entire casting, dropping in the assembled arbor, and then the result onto the OEM'ed motor to be the most efficient assembly process. It would be interesting to determine what Ryobi had stated as a repair procedure to its service technicians.

              Comment

              • mmcmac
                Forum Newbie
                • Nov 2014
                • 53

                #8
                Originally posted by I saw that!
                Very industrious.
                Now show us how to safely remove (no cutting, no heat) the #7 bearing from an arbor having a solid #5 pulley. If you can find effective/durable jaws that thin, I want some. Btw, the bearing needs to be removed via inner race to minimize damage potential so it can be reinstalled. Good luck with that.
                I'm sure someone could find a way, but from a practical perspective such a non-destructive extraction technique would need to be less cost/work compared with replacing both itself and perhaps another bearing on the arbor which as well hasn't yet failed. My thinking was if the arbor needs to be disassembled to replace one failed bearing, the life expectation of the remaining two probably isn't much longer. I think the bill for all 5 RBI bearings was about $17 delivered. So I didn't give it a second thought. Incidentally I didn't find the motor bearings documented anywhere. At least on the 15A motor I'd rebuilt the rear bearing is 6200ZZ and front is a 6201ZZ.

                P. S. I tried spreading the #6 ring open with external ring pliers, et al, in an attempt to use the pulley to force the bearing off, but I couldn't keep my tools from slipping off the ring ends, so I never got it out of its arbor groove. Maybe you'd have better luck with that method than I did.
                I didn't capture any pictures of the arbor disassembly process, however I'd used a two piece dished bearing separator to pull all bearings except for #8 which came off with a conventional puller. In all cases the old bearings were destined for the junk box so I made no attempt to avoid axial loading when removing them. I've attached a picture of the puller used to remove the remaining four bearings and the arbor pulley.
                Attached Files

                Comment

                • mmcmac
                  Forum Newbie
                  • Nov 2014
                  • 53

                  #9
                  Originally posted by I saw that!
                  I agree they likely did heat the motor bracket, but this would have been in well-controlled conditions and using a jig for precise alignment during insertion.

                  Not having such equipment at my disposal personally, I'd fear improper technique. Did I get that bore heated equally all around or was the left side.. oh wait I think I may have tilted the arbor slightly as one side was cooling.. or did I have the heat gun on that side longer than the other and.. oops.. guess I'll find out eventually when there's vibration or whatever.
                  It is a fairly simple procedure. The fit when warmed (as below) is at most 0.02mm over the bore diameter at room temperature. The arbor tail bearing pair will drop in and self align as the casting and bearing equalize in temperature. As an experiment I heated the guide holder to 60*C(140*F) with a hair dryer and was able to drop in its room temperature 6003 bearing with plenty of working time until the fit closed. Given the casting is Al, it will easily equalize out hot spots within the structure as it is warmed. That said, sufficient heat to bring the entire casting up to temperature is needed which OTOH slows cooling of the target area.

                  All bearings are physically captive in the assembly and in practice the saw would likely not be capable of generating a -40*C differential in a Fe bearing relative to its Al casting particularly considering the bearing to be a heat source and the casting a heat sink. I hazard this consideration allowed use of a slight casting bore undersize and the simple assembly procedure.

                  Comment

                  • mmcmac
                    Forum Newbie
                    • Nov 2014
                    • 53

                    #10
                    Originally posted by I saw that!
                    I'd still be interested to learn how someone can safely remove that #7 in the case of a solid pulley. I think the easiest way would be to somehow get that ring out of its groove then use a normal puller on the pulley and drive the bearing off that way.
                    Could a tempered wire be threaded in each index hole of the C clip and then used to open it up? Perhaps pull it beyond it's elastic limit to open its diameter such that when out of the groove it would better sit on the larger shaft within its intended plane? If so I'd then leave it in as it would insure pressure during removal off would be directly in the inner race.

                    Comment

                    • mmcmac
                      Forum Newbie
                      • Nov 2014
                      • 53

                      #11
                      Originally posted by I saw that!
                      At any rate, I won't waste more time experimenting, since I'll be replacing the pulley -- I'll just cut that off.
                      I might have another go pulling the C clip out vs. cutting the pulley off. Using this cabinet shop abused saw as a barometer, I'm getting a glimpse into wear concerns for the machine. The pulley seems to have assorted dings apparently from repeated meetings with hard chips. I'm wondering if it is at the point where I'd should put in on a lathe and clear up the minute burrs in order to reduce wear on the urethane belts. If I had a spare pulley I certainly would have pressed that on to get the saw back in service and get to clean up of the pulley at some later point.

                      Alternatively if I had a spare solid pulley on hand that might be a candidate for machining to a new belt profile if need be.

                      Comment

                      • capncarl
                        Veteran Member
                        • Jan 2007
                        • 3564
                        • Leesburg Georgia USA
                        • SawStop CTS

                        #12
                        If you clean it up much your new belt might be loose. I'd just touch it up with a file and sandpaper. I saw at Lowes in the Christmas gift section a nice looking set of assorted small files, tapered, pointed and diamond.
                        Not their usual stock items. Real good for this purpose.
                        capncarl

                        Comment

                        • mmcmac
                          Forum Newbie
                          • Nov 2014
                          • 53

                          #13
                          Originally posted by capncarl
                          If you clean it up much your new belt might be loose. I'd just touch it up with a file and sandpaper. I saw at Lowes in the Christmas gift section a nice looking set of assorted small files, tapered, pointed and diamond.
                          Not their usual stock items. Real good for this purpose.
                          capncarl
                          I was thinking rather of grinding a cutter to equal the v-belt 40* profile and using it to clean out the 1.6mm pitch pulley grooves. This would be similar to a threading operation except the tool would be moved in discrete 1.6mm steps. A glancing cut over the pulley afterwards will knock off any remaining burrs. Unfortunately at this point I have the arbor mounted in the motor bracket so any cleanup operation in a lathe will certainly be more interesting.

                          The urethane belt is a Bando H profile multi ribbed urethane V belt. The Bando catalog page is attached here for reference.
                          Attached Files
                          Last edited by mmcmac; 12-19-2014, 07:06 AM. Reason: clarity

                          Comment

                          • mmcmac
                            Forum Newbie
                            • Nov 2014
                            • 53

                            #14
                            Originally posted by mmcmac
                            ..clean out the 1.6mm pitch pulley grooves.
                            There is the possibility this saw is an outlying data point w/r/t resulting pulley wear. I've only removed the belts on this saw for close inspection, but found what appears to be uniformly coloured hard black chips lodged between the belt V grooves. I first thought it perhaps started as wood chips which were then friction charred during blade stall. But I'd expect blade stall to result in motor pulley slip which would likely need to be quite repetitive to create such uniformity. No idea as I'd turned this belt inside out and cleared the grooves with a nylon toothbrush. Fortunately the belt is in far better condition than I'd expected. When I get around to its sibling, I'll take a closer look at the recovered debris.
                            Attached Files

                            Comment

                            • capncarl
                              Veteran Member
                              • Jan 2007
                              • 3564
                              • Leesburg Georgia USA
                              • SawStop CTS

                              #15
                              Soak the pulley down in AWSOME for 15 min and all that stuff will come out with a sharpened stick. No sense risking cutting the pulley grooves.
                              capncarl

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