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  • Wadkin PK

    Hello All, According to the motor shop I took my PK motor to it needs new bearings. In order to help them source new ones
    I thought someone on this site may have a recommendation as to replacements.
    It's a ZEF with double row Hoffman bearings. So far their quote to clean and balance the stator, rebake the windings, bring new leads
    out and new bearings is $900.00 Yikes, I don't think that I will be keeping the saw after this! Anyway any help is appreciated.
    Barry
  • Thread Continues Below...

  • #2

    Re: Wadkin PK

    Wow. Have you tried anywhere in the states? I will see if I can find some old connections. I will be going thru my motor shortly. Windings are often painted with Glyptol and baked. Hot rod shops and woodworking tool vendors often balance shafts. Try Vexor in denver and Kaiser enterprises in denver. Not sure why you feel you need to rebalance the rotor shaft. Anything wrong with it? As for stator windings, sometimes these need to be steam cleaned in which a little baking is needed. I took my 7.5 hp dewalt motor to boulder electric motor after sitting under a spruce tree for over ten years. Cleaning, rotor bar verification, stator cleaning and new bearings cost 165 dollars us.

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    • #3

      Re: Wadkin PK

      Originally posted by BMILNE View Post
      ...So far their quote to clean and balance the stator, rebake the windings, bring new leads
      out and new bearings is $900.00...
      That may not be a bad price. I've heard that the cost of the larger bearing alone can be $750 (but can't remember which model of PK motor that was for).

      Cheers, Vann.

      Proud member of the Wadkin Blockhead Club.

      Comment


      • #4

        Re: Wadkin PK

        The ZEF had a 6210 front bearing and a self aligning 1306 on the back. On ebay the 1306 with polymide cage ( you don't need brass or steel ) is in the 50-75 range USD. A good open 6210 will be under $100, maybe a little more if precision with a phenolic cage. I had my ZEF rewound for $500 and put the bearings on myself. An RHP 6210P4 or a Fafnir mm210 are both ABEC 7 which is way better than you need but still my choice for a PK ( because a PK deserves the best. Dave

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        • #5

          Re: Wadkin PK

          Wonderful bearing information. This is why I love this site. My 1949 nothfield heavy 12 jointer had the Louis allis motor rewound by the PO so I don't know the cost. But the workmanship is top flight. It's a brand new motor. The work was done by Kirby Risk Electric Repair in the states. They seem to have about four locations. I personally buy my bearings from Whisler bearing in denver. They had the large end oliver 299 bearing in stock from SKF and it was about 180 dollars. Not bad for an abec 7 bearing about 6 or 7 in in diameter. Most modern bearings today are made to abed 5 or 7. No business case to make the same bearing in abec 3 or less. They just change the package and charge accordingly. Abec 9 precision bearings are a bit more inspected and made a bit tighter but you pay for it. As I said, I have yet to dive into my pk motor to see exactly what animal I have.

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          • #6

            Re: Wadkin PK

            My biggest concern right now is with the motor windings. The motor was made for the English power grid. I want to to use a vfd but I am not sure how this will work yet. The down side is that the pulse width modulation methods in the vfd may set up induced voltages in the rotor which have no choice but to discharge to ground thru the bearings and frame. It can take a 100,000 hour bearing and turn it into a 720 hour bearing. I am doing further research as we speak and this issue is new to me so I am no expert here. I will be dealing with kirby in the near future to figure out how to handle the pk motor.
            Last edited by emchdev; 02-28-2020, 06:20 PM.

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            • Thread Continues Below...

            • #7

              Re: Wadkin PK

              I would not worry about the vfd use on the wadkin motor, can we assume you have researched the subject on OWWM forum? How many hours per month do you expect to run the saw?

              Comment


              • #8

                Re: Wadkin PK

                It's generally not the balls that determine the precision. The concentricity of the inner and outer race are also in play. An ABEC 1 is a much better bearing than an ABEC 1 made 50 years ago but it is still an ABEC 1. The cage design and material are issues too. No matter the precision, a stamped steel age bearing can only run a certain speed and the much of the benefits or the precision are lost. A machined cage, steel, brass, or phenolic, probably in that order, can all run at a much greater speed and deliver the benefit of the higher precision. It is difficult to find a machined cage bearing in less than ABEC 5, P5, and it is difficult to find a stamped steel cage bearing in a precision higher than ABEC 3, P6. The beauty of the old machines is they were designed for open bearings and can dump excess grease yet retain the proper amount to operate. That opens up a whole world of expensive bearing choices that can be found pretty cheap if you know the nomenclature. Precision is also irrelevant in a self aligning bearing although I try to avoid C3 clearance in those. English machines liked SA bearings while most of my US machines avoided them. Dave
                Last edited by beckerkumm; 02-29-2020, 08:55 AM.

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                • #9

                  Re: Wadkin PK

                  Originally posted by beckerkumm View Post
                  Precision is also irrelevant in a self aligning bearing although I try to avoid C3 clearance in those. English machines liked SA bearings while most of my US machines avoided them. Dave
                  To me a self aligning bearing locks onto the shaft rather than a press fit? I have never seen such a bearing in a motor? This motor only turns 3600 rpm so it is not as demanding as say a spindle bearing that runs 20k rpm!
                  Rob

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                  • #10

                    Re: Wadkin PK

                    The 1306 on the ZEF motor is self aligning. Robinson used SA bearings on both ends of my ETE. I see them most often on direct drive applications where there is distance between the bearings. The SA compensate for slight machining inaccuracies. Porter, who used the best ABEC 7 bearings ( and ugliest paint ) ran deep groove until the 36" size where they went to SA. Evidently they felt comfortable with their machining on a 30" head but not the 36". Dave

                    Comment


                    • #11

                      Re: Wadkin PK

                      The motor shop has the ZEF apart and is waiting for me to tell them what quality of bearings to install. They can do cheap or expensive. The response from beckerkumm
                      above sheds some light on choices. Are the 1306 and 6210 bearings equivalent to the original Hoffmanns? I don't want to go overkill on the bearing cost but do want
                      a good set installed. I originally took the motor in because one lead was broken, and figured they could bench test it and check and regrease the bearings.
                      Barry

                      Comment

                      • Thread Continues Below...

                      • #12

                        Re: Wadkin PK

                        The 1306 will be standard polymide cage, normal clearance. The 6210 is where you have lots of choices. If you are ordering new and don't want to spend new high price for precision, I'd go with an SKF explorer. At 3600 rpm you will be fine from an operating standpoint. Depending on who you buy from it may be cheaper to buy shielded or sealed and take off the shields or seals. The motor guy might recommend keeping the seal or shield- your call. If I'm bringing a motor to a shop I always bring my own bearings as motor guys tend to get the clearance wrong but I'm fussy with old stuff. I put an RHP phenolic ABEC 7 in mine but only because the original was a machined brass and I found the RHP on ebay for about $100. Dave

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                        • #13

                          Re: Wadkin PK

                          Originally posted by beckerkumm View Post
                          It's generally not the balls that determine the precision. The concentricity of the inner and outer race are also in play. An ABEC 1 is a much better bearing than an ABEC 1 made 50 years ago but it is still an ABEC 1. The cage design and material are issues too. No matter the precision, a stamped steel age bearing can only run a certain speed and the much of the benefits or the precision are lost. A machined cage, steel, brass, or phenolic, probably in that order, can all run at a much greater speed and deliver the benefit of the higher precision. It is difficult to find a machined cage bearing in less than ABEC 5, P5, and it is difficult to find a stamped steel cage bearing in a precision higher than ABEC 3, P6. The beauty of the old machines is they were designed for open bearings and can dump excess grease yet retain the proper amount to operate. That opens up a whole world of expensive bearing choices that can be found pretty cheap if you know the nomenclature. Precision is also irrelevant in a self aligning bearing although I try to avoid C3 clearance in those. English machines liked SA bearings while most of my US machines avoided them. Dave
                          My problem is that to me, a bearing is a bearing, is a bearing...

                          For the few replacement bearings I've bought for my Wadkins, I've never been able to find an ABEC rating (and if I did, I wouldn't know what's suitable ), let alone the P5/P6 rating. The best I'm able to do is use the rule of the thumb Jack suggested: if it's got a brass cage then the quality won't be too bad. Whether a brass cage makes them the most suitable is another story I suppose.

                          For example, when I went looking for replacement bearings for my RB surface planer (jointer)...
                          Originally posted by Vann on the Aussie forum
                          ...From Andy RV's thread (on CWW) I believe the bearings are SKF 2306 Double-Row Self-Aligning bearings at each end. Looking on a certain auction site, I find various versions of the 2306 bearing:
                          - 2306 M (these seem to have a machined brass/bronze cage);
                          - NUP 2306 ECP;
                          - 2306 E-2RS1TN9;
                          - 2306 K
                          etc.
                          So now I'm confused

                          How do I tell what ABEC these are (and what ABEC standard should I be looking for anyway)?
                          In the end I bought two 2306 M bearings because of the brass cages.

                          What would be particularly useful would be for someone in the know to post a range of suitable bearings for the more common Wadkin replacement bearings, such as:
                          - Wadkin PK (ZF motor): RL 16 & RM 9 bearings;
                          - Wadkin PK (ZEF motor): 6210 & 1306 bearings;
                          - Wadkin RB, RD, RM etc: 2306 bearings (for cutterblock).

                          Are bearings with seals/shields removed as good as open bearings (smaller balls in some/all cases)?

                          Anybody who could help with this would be much appreciated.

                          Cheers, Vann.

                          Proud member of the Wadkin Blockhead Club.

                          Comment


                          • #14

                            Re: Wadkin PK

                            I had to get new bearings for my ZF motor and I had to compromise. The big one was going to be £28O. I got original spec Hoffman for the small one and cheap for the big for a total of £1OO for both.
                            My motor guy will alter the windings to run on 22Ov for £5O. Sometimes its not possible because of the hard brittle bitumen they used
                            www.wadkinrestorations.co.uk

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                            • #15

                              Re: Wadkin PK

                              Self aligning bearings don't often have ABEC ratings- at least that I can see. The nature of the bearings and races being able to adjust and stabilize kind of negates the benefits of precision. The balls need to be held in a cage to stay in alignment so the cage material is important. Older bearings were steel, brass or bronze, and newer are polymide which is kind of a tough plastic but supposedly has less friction and wears longer. The travel of a sealed SA bearing is limited by the seal but generally the shaft isn't out of alignment with the other bearing enough for the seal to interfere. I'm not fussy about the cage material but I try to keep normal clearance to minimize any slop in the spindle. I think I can see a slight wiggle in my Robinson blade at start up but it is tight at speed. You will find SA in normal or C3 ( loose ) clearance.

                              The smaller the bearing the higher the speed limit and the lower the load rating.

                              The main difference between a standard bearing and a precision one is the limiting speed. Load ratings are the same, whether sealed, open, or precision. When you look at modern machines vs old you see that large open bearings handle far greater loads but at slower speeds than smaller sealed bearings used today. Particularly true in shapers which need relatively high speeds in the spindle vs a table saw. A precision 6210 like the ZEF runs has a speed limit of 14300 rpm in grease vs 4800 for a sealed standard and 7100 for a shielded. Not a big deal on a 3600 motor but important for a shaper.

                              A way manufacturers today compensate when using a standard bearing near the top of its speed limit is to increase the clearance between the balls and races. The inner and outer are never totally concentric so there will be tight and loose spots around the circumference where the balls rotate. By increasing the clearance, the tight spots get farther apart which keeps the bearing cooler. The downside is you need to run the bearings to heat them enough to tighten up that clearance so the bearing doesn't add runout to the spindle. I see C3 clearance on shielded bearings and C2 tight clearance on a precision bearing. You have to decide what quality bearing fills the need of the machine.

                              Deep groove or radial bearings are the design that has the most choices in precision, cage material and type, and clearance. Since there are no load differences within any size, it is mainly a balance between speed and clearance, with the cage material and design contributing to the choices. If I can find a brass or bronze machined cage bearing, it will likely be ABEC 3-5, and maybe higher. A phenolic cage will be ABEC 5-7 ( seldom look for a 9) and the clearance will usually be normal ( CN or no designation ) or C2 ( tight ). Once in a great while I'll see a C1 but I don't know what I'd need them for so I ignore.

                              As an example,Whitney liked using 6311 in their machines. A sealed standard has a speed limit of 4000 rpm which is too close to the motor speed for my taste since try to avoid C3 clearance. A shielded has a limit of 5600 which is what I use in my 77 slider ( could never find a precision 6311 for a decent price ). The load capacity of the 6311 is double that of the 6210 in the ZEF. Originally Whitney ran that bearing in oil which increased the speed limit to 6700- until you tilted the arbor and the oil ran out. Whitney also used the 6311 in their shapers but with a precision oil bath and a speed limit of 15100.

                              Although this is rambling it is pretty basic as is my knowledge. I watch for old open bearings in sizes my machines use and buy when I find a deal. Inch bearings are hard to find and even harder to find a deal on any precision. Angular contact is a whole different discussion but most are precision and contact angle is what is important for the application. Bandsaw and sliding table bearings move so slow I'm not particular. Oil bearings have a sound I really enjoy - or at least did when my hearing was better. I try to never install a worse precision than the machine came with and never trust that the bearing in the machine is the correct one.

                              Dave
                              Last edited by beckerkumm; 02-29-2020, 10:23 PM.

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