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  1. #21
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    Hi All,

    Success! Punched out one pin on the power feed shaft and drilled the second. Following Ross’s suggestion I went directly for the impact driver to remove the last screw holding the bearing retainer plate. Nice and easy.

    You can see in the pictures the amount of rust/oil/grease mix in and around the bearing. Quite nasty.

    Now for the puzzle, popped of one of the seals from the bearing, it only has a small amount of the rust mix inside, in fact it is quite good and spins nicely. No sign of rusting, pitting or anything else wrong. So much so that I wonder if the rust didn’t come from the bearing. When I received the machine the spindle handwheel at the back was missing and was replaced with a loosely fitted bolt/washer. This bolt normally sandwich’s the handwheel, drive pulley, coolant pump sprocket and the inside race of this bearing to a step on the shaft. All these items were loose on the shaft.
    The rust mix is spread all over the inside face of the main drive pulley and along the whole shaft outside of the gearbox. The shaft itself looks ok, no sign of pitting or rust in the surface. I do think that there has been some fretting occurring on the shaft.
    I think that I will re mount the pulley and sprocket with some loctite just to stop any movement.
    beee8ed6-852e-4907-a96a-029d41f774c1.jpg48f14c10-404f-4b04-8aec-8b0b7b012960.jpga98d8b4e-d2fd-4cf1-8199-a5e1d18f6572.jpga98d8b4e-d2fd-4cf1-8199-a5e1d18f6572.jpgb168e19f-228d-4df9-b363-baacbe7a6095.jpgb168e19f-228d-4df9-b363-baacbe7a6095.jpg435bde6d-e33f-419d-bd1e-d4f3ba566bb1.jpg

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  3. #22
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    Well I should have looked a bit harder before posting.

    Shaft is worn where the unrestrained items have been moving. The bearing may have been spinning on the shaft a little. There is a hardened washer between the bearing and the step in the shaft, it has deep groves worn in to it to match its contact points.

    The rust, I think this may have all been caused by the fretting. The bearing retainer plate is set up with a channel to catch oil that comes through the bearing and return it through a drilling in the main casting to gearbox, it would let the rust through. This setup seems to be for a non RS bearing so I think I should block it when doing the re installing.

    So any suggestions on how to proceed?

    The shaft has a reduced diameter, I will attempt to measure it and the matching parts.

    How big of a gap can loctite bearing retainer be expected to deal with? Is there something better?

    It seems a little strange that this whole stack of components is held together by a plastic handwheel.

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  5. #23
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    Rust color is actually the result of the fretting....Sorry for your troubles.
    Absolute solution: remove the shaft and send out to be hard chromed and ground back to original size....Slight undercut (with radius) at each end of the damaged area....no need to chrome more than needed.
    Make the undercut .010" -.020" undersized over original...need enough wall for this to be a good repair. Don't go crazy....thick = $$$$

    Could also go for metal spray...to build up the damaged area. This is a fine application for a spray metal build up as the part is cylindrical. Usually needs a prep of the surface like a roughing cut to give the surface texture.
    I would avoid any sort of welding build up .....long shaft, just too much possibility of warp age.

    Loctite bearing mount gets lots of support as a repair solution....I don't find it as such. Have seen Loctite used Lots of times as a repair solution on old car parts on shafts and bearing fits that are worn...when that structure is re-visited almost always the Loctite is no where to be found...its not a solution that i put much faith in,your results may vary.

    As to the plastic hand wheel.....should have a molded in steel inner hub that the retaining bolt bears against.....should not be a problem getting it tight enough to retain all the shaft components...

    Cheers Ross

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  7. #24
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    Hi Ross,

    Thanks for chiming in. You are quite correct, caroming the shaft would be the best repair. Not to forget the pulley would need to be sleeved as well.

    I’m inclined to go with the loctite for now. I haven’t yet even put power to the machine and don’t know what else lies in store. So I think it would be a good idea to do a basic repair at the moment, mostly just to get it going and also to prevent any further damage. Then I can see what else needs to be done and get a solid plan together. I expect some other surprises.

    I’m going to take a step back for the rest of the weekend. But of time to contemplate.


    Forgot to add, I have had a bit of a go at measuring the shaft and bores, not happy with the bore measurements, will try again on Monday before posting them here. The shaft measured 24.98mm on a unworn section. The smallest bit I could find was under the pulley at 24.92mm.
    Last edited by Boat Brat; 05-23-2020 at 06:23 AM. Reason: Added some dimension

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    Ross
    Did you have had loose bearings that were loctited in place regulary ??
    Never had that problem At least not if the wear is just a few 0,01mm Loctite for bearings works great Sometimes too great I have had more problems removing bearings So I would not use the strongest loctite on the OD A gap of 0.05mm should not be a problem in my experience One bearing on a shaft with loctite should make thermal expansion still possible

    For the pulley I replaced it with a taper lock pulley once Worked great

    Peter

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    Peter:
    Yes i have had issues with Loctite not retaining the part it was applied to.....
    Given that most were applications that one might count as severe or tough...Like holding an axle bearing in a loose housing ....rear wheel outboard upright on a formula car..done.more than one.
    Loose pinion bearings for a Hewland transaxle gearboxes....etc....just does not seem to work. Finally gave up on that solution for these problems....
    Perhaps the clearances were too large....don't have any numbers in my head just now.
    General lac of success with this style repair has prompted a shop wise saying....."Glue and magic potions are no substitute for a good mechanical fit".....
    The Loctite products are magic for retaining studs, an preventing threaded assemblies from becomming loose in service...i use them all the time. The retaining products not so much.
    Cheers Ross

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    Quote Originally Posted by Boat Brat View Post
    I haven’t yet even put power to the machine and don’t know what else lies in store. So I think it would be a good idea to do a basic repair at the moment, mostly just to get it going and also to prevent any further damage. Then I can see what else needs to be done and get a solid plan together.
    I think that's wise. You need to get the machine in use so that you can identify any other significant problems.

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    Quote Originally Posted by AlfaGTA View Post
    Peter:
    Yes i have had issues with Loctite not retaining the part it was applied to.....
    Given that most were applications that one might count as severe or tough...Like holding an axle bearing in a loose housing ....rear wheel outboard upright on a formula car..done.more than one.
    Loose pinion bearings for a Hewland transaxle gearboxes....etc....just does not seem to work. Finally gave up on that solution for these problems....
    Perhaps the clearances were too large....don't have any numbers in my head just now.
    General lac of success with this style repair has prompted a shop wise saying....."Glue and magic potions are no substitute for a good mechanical fit".....
    The Loctite products are magic for retaining studs, an preventing threaded assemblies from becomming loose in service...i use them all the time. The retaining products not so much.
    Cheers Ross

    Ross
    I disagree
    I can assure you the product works fine for the purpose it was meant for
    The examples you mentioned had to much play then or are overheated Over 160dgr C it loosens its strenght
    Bearings assembled with loctite you eighter have to heat up or use a decent press
    A 50 ton press fails to press out a bushing 100mm OD and 100mm long Probably smaller ones too

    Another thing with bearings is that the stationary race has a pretty loose fit from the get go
    That is according OEM standard So people think it is too loose while in fact it is not

    Peter

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    Peter:
    Your real world experience is different than mine....
    Not all bearing fits on the outer race are the same.....not all bearings are mounted into cast iron!
    Cheers Ross

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    Well, loctite is no magic fix all. It has its place and very much it’s limits. If you work well within these limits it can be a “magic” solution.

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    Hi All,

    In between the bearing and the step in the shaft is a special washer. It seems to serve 2 duties. one is the step on the shaft that stops the bearing is quite small, it would catch the bearing on the radius between the bore and flat face. The other use is as a end stop for the gears that rotate on the shaft.
    This washer is hardened and ground.

    It has suffered quite allot from the loose bearing, I have attached a picture of both sides, these I believe should both be flat. The circular groove has been worn in by the bearing inner race.
    48b0fed1-960d-474c-9f1a-3d1f5b19896a.jpg
    8f7d42d2-b05c-469a-a412-48995e14328a.jpg
    I need to replace this washer. I have had a look on Franzís website without luck. I assume he will find/make one on request. Not sure how long this will take, not to mention the shipping issues at the moment.
    option 2 have a copy made locally. Iím sure I can find someone who can harden and grind.
    Option 3 Make one myself, I canít make a hard one. Can get some 4140 locally and make it from that. Not sure if it is up to the job and canít inspect easily.
    Option 4 find something to modify, a standard shim? Needle thrust race washer? 3mm thick, 25mm inside. od doesnít seem to be to important, original is 38mm space for more. Anyone have an idea what I could use?

    Option 200.... get of my a$&)and get the myford mg12 operational.....

    Leaving out option 200, will a soft washer be ok? Iím leaning no but would like some other points of view.

    Thanks.

  17. #32
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    Hi All,

    Well I went with option 4. I found a SKF roller thrust bearing race that was a good size, it is a few mm larger in OD but this won’t be a problem. The original had 2 grooves cut in it for oil. I cut 3 in to the race using the only thing I had available, a proxxon cutoff wheel. Worked a treat!6506af63-fdaa-4ef4-8311-a4e64bbbeda2.jpg
    I did send an email to Franz about this part, I haven’t yet heard back (4 days) does anyone know if they are working at the moment? Or closed due to covid?
    I have not yet had a chance to fit the new washer as I have gotten a little sidetracked....
    So, I was contemplating how to change the oil wicks in the Y axis. One thing lead to another and now the machine is headless!
    Vertical spindle came off easy, had to make a wooden cradle on the table to support it as I’m working alone. 2 guys could probably do it by hand.
    Horizontal spindle, Y screw and gib are out. Just need to support and unbolt the glass scale.

    FYI. The Y ram has at least 4 oil wicks that I have found so far. 2 near the gears that you can see from the top and possibly replace from there and 2 in the back visible when the bracket for the Y screw is removed. I don’t think you can replace these with the Y in place, to far in.

    While I’m this far in I will most likely replace all the bearings in the Y ram. From what I have been able to see so far these are all open. Any reason to not replace them with 2RS bearings? Lubrication seems a little on the minimum in this area.

  18. #33
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    Hi All,

    I’m trying to figure out how to adjust the backlash on the Y nut.d0dbd144-9ff6-4ef7-86e7-cadf39d09719.jpg
    I thought I had seen a thread about it but have been unable to find it again. Dose anyone remember the thread? Link?

    Thanks.

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    Hi,

    In a similar line to my last post. Today I reinstalled the Y handwheel shaft.c7fa2cf6-ec11-47ef-a21e-dff73b39667c.jpg
    It has a couple of shims to adjust the backlash on the bevel gears. There was a bit much backlash so I ended up removing one (0.2mm) now the backlash on the gears is almost nothing..... is that going to be ok? Or should I leave a little for thermal expansion?

    Thanks.

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    Quote Originally Posted by Boat Brat View Post
    Hi,

    In a similar line to my last post. Today I reinstalled the Y handwheel shaft.c7fa2cf6-ec11-47ef-a21e-dff73b39667c.jpg
    It has a couple of shims to adjust the backlash on the bevel gears. There was a bit much backlash so I ended up removing one (0.2mm) now the backlash on the gears is almost nothing..... is that going to be ok? Or should I leave a little for thermal expansion?

    Thanks.

    Almost nothing is fine. Nothing is not
    The backlash in the nut itself can not be adjusted But the thrustbearings that retain it can with the 3 setscrews in the flange
    That neadle thrustbearing behind the nut I would check as it is in bad condition often
    This is bad design IMHO

    Peter

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    I think Peter is correct about all points. The 3 setscrews in the flange are there to take up any play in the thrust bearing behind the flange. I would leave very little clearance in that bearing.

    Quote Originally Posted by Peter from Holland View Post
    That neadle thrustbearing behind the nut I would check as it is in bad condition often.
    On my machine that is a ball thrust bearing not a needle thrust bearing. But it was in bad condition. When I first looked at it, I thought all was OK. Then I realized that one of the ground rings had a radial crack running all the way through it. Probably happened during a Y-axis crash. Easy to do until you learn to avoid the vise or place it out of reach of the Y ram. Good news is that these bearings cost about the same as a good cup of coffee!

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    Hi Peter,

    Thanks for the confirmation. I just didn’t want to mess anything up.
    I have had everything in that area out, thrust bearings look ok. The screw is ok but not great as in the nut. Plan is to get it in operation without causing damage due to grease and sludge(everything in the area is well greased). Then some time later replace the screw, nut and thrust bearings. All in that is about 2k so not rushing in to it just yet!

    Any tips on adjusting the 3 bolts and screws for the thrust bearing? I’m not sure how to get everything parallel and without preload.

    Thanks.

  23. #38
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    Hi Ballen,

    Thanks for the reply.
    Interesting that both you and Peter have had problems with that particular bearing. Makes me wonder if I should pull it again and have a good look with a magnifying glass.
    Im surprised that it is just a standard bearing and not some higher precision one.

    Regards.

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    Quote Originally Posted by Boat Brat View Post
    Interesting that both you and Peter have had problems with that particular bearing.
    Peter is a pro and sees and fixes a lot of these machines. So when he says it is problematic, there's a good reason.

    Im surprised that it is just a standard bearing and not some higher precision one.
    First, that bearing never turns faster than the lead screw nut, perhaps 100 rpm tops. Second, any play in that bearing just adds to play in the leadscrew/nut. Since those have at least 0.03mm of play (and probably more like 0.2mm) there is absolutely no need for precision in that bearing.

    In your shoes, I would not spend 2k replacing the lead screw and nut. I'd at most spend $10 on a new thrust bearing, and spend the remaining the money on a good DRO, at which point the backlash in the lead screw and nut is more-or-less irrelevant.

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    Hi Ballen,

    Yes, but you haven’t seen the screw! I have been trying to figure out what they have done to it. The majority of the thread flanks look fine, but in the middle third of the screw it looks like someone has gone over the tops of the thread with a coarse file! No idea what happened. It dose seem to be straight and the parts of the thread that matters is not to bad. Still annoying.
    Machine has the original aktiv DRO, hopefully it is still working.

    Will get a picture of the screw tomorrow.


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