Announcement

Collapse
No announcement yet.

New Electric Motor Bearings

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • New Electric Motor Bearings

    As part of my teardown on the Millrite I just brought home, I tore into the motor today. When I tested the machine it was noisy at startup and I assumed dry bearings. After inspection I was proven correct - the top end bearing is completely dry and very noisy. The PTO end spins freely and takes forever to spin down, but it has the slightest noise and there is enough wobble between the inner and outer race that I think it needs attention too. Now it is just a matter of getting the right bearings, and that's where my questions are.

    I remember once reading somewhere that bearings for electric motors have a different designation that conventional bearings. Is that related to the grease, seals, precision, or some combination of these? I've pulled the information off the bearings, but how do I know that what is in there is correct for an electric motor, and not just a generic bearing of the correct size? The bearings in the motor are as follows:

    top bearing: NSK 77203
    bottom bearing (PTO): Nachi 6204Z

    Do I just go out and buy bearings that exactly match these, or do I need to look for something else? This motor is only a 1200RPM motor if that makes any difference.

  • #2
    An "electric motor" rated bearing is usually just selected based on quiet running. For most intents, not an issue if you put in quality bearings of the same number. BTW.. Nachi and NSK are quality brands.

    Are you sure the bottom bearing is a Z (single shield) or a ZZ (shield both sides?

    The top bearing number isn't computing.. what are the measurements (metric)? That may be an old Hoover number and I'm pretty sure that would translate to a 6203ZZ
    Last edited by lakeside53; 02-12-2015, 08:18 PM.

    Comment


    • #3
      If you have a Motion Industries near you, give them a call with your bearing numbers. They'll either get you those bearings or be able to tell you the equivalent. 203 and 204 bearings are pretty common and should be on the shelf.
      Stuart de Haro

      Comment


      • #4
        Hi
        Is this a vertical shaft motor Then the bearing MAY!!! be a 7203 angular contact bearing 17mm*40mm*12mm
        Or a 6203 2RS
        Be aware that this bearing also can have a 5/8 bore so take the bearing when you go to purchase new ones.

        Eric

        Comment


        • #5
          NSK bought Hoover in the 70's and for a while overlapped Hoover numbering. If it's the Hoover number it's just a 6203ZZ radial bearing. Hoover would have put a -625 after their number if it was a 5/8 bore, but yes, be careful and measure the shaft at the bearing location.

          Comment


          • #6
            It doesn't really matter if you replace the bearing with a shielded or sealed bearing. I prefer the sealed to the shield for the simple reason the seals can easily be removed for greasing and the shields, well good luck !!! Nothing fancy or precision about those two motor bearings. I have found that some motor bearings have metric bores.

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

            Comment


            • #7
              This is a vertical shaft motor. The currently installed bottom (pto) bearing is a 6204Z (I'm pretty sure it was labeled Z and not ZZ, even though it is a double shield). Logic would dictate that this bearing is taking the bulk of the downward force of the rotor, so should this be a 7-series bearing instead of a 6-series? Is there any reason why you couldn't put a 7-series in anyways? I found information about how the 4 digit bearing codes work, but how does a 5 digit code such 77203 work?

              As I said, I don't know a lot about bearing codes, but how can some 6203 bearings have a 5/8" (16mm?) bore? doesn't the "03" indicate a 17mm bore? I'm going to measure everything before I order to make sure, but I think the sizes of the bearings sound correct. In my case it's not a case of going to a shop and comparing before I buy because it's too rural here to have anywhere within easy driving distance to get them. I'll more than likely ebay them and have them in the mailbox early next week.

              Originally posted by velocette View Post
              Hi
              Is this a vertical shaft motor Then the bearing MAY!!! be a 7203 angular contact bearing 17mm*40mm*12mm
              Or a 6203 2RS
              Be aware that this bearing also can have a 5/8 bore so take the bearing when you go to purchase new ones.

              Eric
              Last edited by lost_cause; 02-12-2015, 10:39 PM.

              Comment


              • #8
                The 6402Z is just a plain radial bearing. It will take a fair amount of side load meaning that the weight or load of the vertical armature is nothing.
                I've replaced bearings in many vertically mounted motors and have never noticed any special type bearing in any of them, unless it was a special application.

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

                Comment


                • #9
                  The 5 digit 77203 code is obsolete. It's now 6203zz. The 7's have NOTHING to do with angular contact. The "3" means 17mm, BUT can be overridden to be 1/2, 5/8, 12,13, 16 or anything someone in the USA wants.! 99.9999% (approximately!) of the 6203 bearings will be 17mm.

                  Just put in 6204zz. Don't put in a 7204 - never mind the problem with shields, you'll never get the preload right anyhow so it will be looser than a 6204!
                  Last edited by lakeside53; 02-12-2015, 11:38 PM.

                  Comment


                  • #10
                    Originally posted by lakeside53 View Post
                    The 5 digit 77203 code is obsolete. It's now 6203zz. The 7's have NOTHING to do with angular contact. The "3" means 17mm, BUT can be overridden to be 1/2, 5/8, 12,13, 16 or anything someone in the USA wants.! 99.9999% (approximately!) of the 6203 bearings will be 17mm.

                    Just put in 6204zz. Don't put in a 7204 - never mind the problem with shields, you'll never get the preload right anyhow so it will be looser than a 6204!
                    ok, that explains why i couldn't find anything to explain that 77xxx code. i wonder if that means that the bottom bearing has been replaced once too? i'll order up a 6203zz & 6204zz today and that will be done.

                    Comment


                    • #11
                      Probably. It is pretty rate for mixed brands in a motor.

                      Comment


                      • #12
                        Originally posted by lost_cause View Post
                        ok, that explains why i couldn't find anything to explain that 77xxx code. i wonder if that means that the bottom bearing has been replaced once too? i'll order up a 6203zz & 6204zz today and that will be done.

                        Of course you will first measure the 77203 an make sure it's 17x40x12mm

                        Comment


                        • #13
                          Originally posted by lost_cause View Post
                          I'll more than likely ebay them and have them in the mailbox early next week.
                          YMMV. Needed bearing for a drill press quill, checked Fleabay. On Amazon, NOS Hoover bearings were cheaper than anything I could find on Fleabay (China import).

                          Comment


                          • #14
                            Originally posted by Rosco-P View Post
                            YMMV. Needed bearing for a drill press quill, checked Fleabay. On Amazon, NOS Hoover bearings were cheaper than anything I could find on Fleabay (China import).
                            yeah, sometimes i'll check amazon, but for these it's hardly worth it. $12.63 delivered for both bearings (nachi - japanese made) from ebay.

                            Comment


                            • #15
                              Be careful of "NOS" bearings. I gotten old stock bearings where the grease is all gummed up, they do have a shelf life. No reason not purchase new brand name motor bearings. I've had great luck with the Japanese Nachi bearings. Last time I priced them 6203-LL were $2.97, 6204-LL were $4.90, 6205-LL were $6.41 and 6206-LL were $7.70 each.
                              Mike
                              Central Ohio, USA

                              Comment

                              Working...
                              X