Why does my MAHO CNC spindle rattle? || RotarySMP

[@steveggca]

Hi Mark , From 6000Km away those bearings look fine. First though I sent you a donation a few days ago but did not see a confirmation, did you recieve it? Looks like you need to buy some new grease😀 assuming the AC bearing turn without roughness I would at least try them again. Rule of thumb for then AC bearing retaining is there should be about 0.025mm of compression , so the bearing cap being loose is defintely a problem.

[@RotarySMP]

Hi Steve, My apologies. your generous donation came in when I was in the middle of the disassembly, and I made a mental note to contact you and thank you. It must have been in the same mental notebook where I said to my wife that I would close up the house in a couple of minutes if she goes out, as all the windows were open to air the place in 5°C / 40°F. She came home an hour later and I was in the doghouse :/ Thanks a lot for you input. I contacted Kluber to ask which grease replaced F23A, and they confirmed NBU15. I still have a bit from the Schaublin bearing regrease, but will need to check if it is enough. Especially as they seem to have put a nice thin coating of grease on all internal surfaces, which has keep the rust almost at bay. Thanks a lot, Steve. Mark ps... where did I put my mental notebook. It must be with those pointy grease adapters.

[@steveggca]

@@RotarySMP Speaking for myself , the worst part of never remembering stuff is continously forgetting that i never remember stuff.

[@WatchWesWork]

I'd triple check the "squeeze" on the outer race of those upper bearings. FAG should have tech specs on how much to squeeze, but it needs a few thou. If it's not enough, you will need to machine the shoulder back on the top retainer (part 10 in the drawing). Those brass caged bearings are prone to "cage rattle". That could also be a source of the noise. I'm really not impressed with that spindle design. Non-serviceable bearing races with no labyrinth seal seems like a recipe for disaster.

[@RotarySMP]

Thanks Wes. Nice to see KZbin nobility drop by :) Another commenter pointed out that those screws elongating would be a symptom of a plunge crash. Since i plunge crashed this machine a couple of years ago, that makes sense. I will source replacement screws. Good point on the clamping stack. Thanks.

[@maikeydii]

​@@RotarySMP You've probably found the root cause of the root cause... :D Plunge crash to elongate and thus loosen the screws, now after few years that results in the upper spindle bearings spinning.

[@selbermacher1267]

Speaking of spindle design, it's also very odd that the locating bearings are on the back and the floating bearings are on the front of the spindle. That way the entire thermal expansion of the spindle gets transferred to the workpiece.

[@orgonewarrior1604]

@@RotarySMP Would you torque test the screws you take out? compare them to a couple of new ones? Great video I'm rooting for the untightening of the screws to be related to vibration and time. Best regards from belgium

[@RotarySMP]

Thanks guys. @orgonewarrior1604 I have ordered the replacement screws and torque wrench as they only need 3Nm, and my current one doesn't go down that far. @selbermacher1267 you are right, any thermal growth will be a variation in Z depth.

[@philhermetic]

Relube and rebuild with the original bearings using minimal bearing glue, torque it correctly and after checking the rest of the head for any possible rattles, reassemble and test! I say this because the strip down was much easier than anticipated , and it would not be a tragedy if you had to strip it again and replace bearings. Can you set up a rig to rotate the quill and listen to the bearings with an engineers stethoscope before you put it back in the head? Given that the noise appeared fairly suddenly I would expect to see damaged bearings, and they look fine! Could be bearing outer spinning in the housing though as that could start suddenly. A thorough inspection of the rest of the head before reassembly is required. Excellent video! On the edge of my seat! Good luck with it! Phil, UK

[@RotarySMP]

Hi Phil, as the gripper is loose in the spindle, I can't really do a partial rebuild and test. It will be a complete assembly to test. I still need to strip, inspect and lube the bevel gearbox bearings as well.

[@owiertacz]

​@@RotarySMP I thought I’d share something: a while ago, I was considering re-greasing the bearings of my new-to-me MAHO MH300M. The manual mentions a 'special grease'-Klüber F23A-which is known to be quite unique, and it's recommended not to use any generic substitutes. Since this grease is no longer available, I contacted Klüber for an equivalent. They were very helpful and dug through their 1970s documentation, ultimately recommending Klüber ISOFLEX NBU 15 as a suitable replacement.

[@brendanshorter5550]

@@owiertacz NBU is what we used on everything. A Saw we had specced it for the linear rails.

[@adagioleopard6415]

Your mason jar inside the ultrasonic cleaner trick came in REAL handy when we needed to wash a bunch of conformal coating off of some old electronics. I saw you using it in a old video and took a mental note, and one day I saw the guys downstairs using acetone and a toothbrush, and I tried out the jar trick and wow did I save them a few days of work with that!

[@jimurrata6785]

Ziploc bag works well for planar things (if they're not too sharp)

[@adagioleopard6415]

@jimurrata6785 acetone might dissolve those if they are the wrong type of plastic though?

[@jimurrata6785]

@@adagioleopard6415 Doesn't seem to do it in mine. 🤷‍♂️ Be careful not to get it over 50° or it will boil and* inflate the bag.

[@RotarySMP]

Good point Jim. Should attentuate the U/S waves less than the glass I guess.

[@adagioleopard6415]

@@jimurrata6785 I've moved on from that job. But they usually used it cold though. So it shouldn't be a problem.

[@Dellpodder]

I'm in alignment with the other comments on the plunge crash stretching the preloading screws, allowing the outer races to slip. If it were me I would replace the screws, relube, and reassemble everything and then check the performance before going any further with the teardown. (If you haven't already seen it, Robrenz has a good video on rebuilding a spindle.) Also I've commented this before but you have cultivated an amazing community of machine tool enthusiasts here!

[@RotarySMP]

Thanks for you kind feedback. Yes, I have watched Rob Renzetti's before, nbut time for a refresher. Thanks.

[@kaibroeking9968]

My father, as a young engineer, was one of the production managers for automotive bearings at Jaeger/FAG in Wuppertal. He showed me that with your fingers and your ears, you can quite precisely do qualitative checks of the inner health of a bearing. A localized imperfection (a speck of debris, a ding, a bit of corrosion) of a few microns can often be felt as a minute sticky spot if turning the bearing by inserting your knuckles in the inner race and turning the outer race slowly with the other hand. If there is no such imperfection to be felt, then the bearings have likely not suffered any localized damage. You should re-lubricate the bearings a.s.a.p. rather than store them in a de-greased state as the surfaces can corrode shockingly quickly. I'd lube them up, re-assemble, adjust the retaining rings until you feel no play and try the spindle under load. Cutting forces will change the load distribution among the bearings and, therefore, which of the bearings does the most work. I had an Emco milling machine that was very quiet when milling at constant depth, but really screamed at me when plunging into material. Changing the upper spindle bearings solved the problem.

[@RotarySMP]

Thanks for your feedback Kai. about what I was planning to do.

[@ChimeraActual]

I worked for New Departure - Hyatt roller bearing for a few years before GM cut them loose in the 1970's. The final QC was done in a quiet room where inspectors listened to bearings being spun. I think @kaibroeking has a good idea, find a quiet room and listen to, and feel, the bearings as you spin them slowly, then quickly. If I were doing it, I'd need some sound amplification...

[@RotarySMP]

@@ChimeraActual My basement shop is pretty quiet, so that should work fine.

[@TheUncleRuckus]

Personally I'd just regrease everything and reassemble it with the bearing retaining compound so it can't spin (then again maybe the bearing spinning is bc the screws were loose) then run the machine through and pit it through its paces to see if the knocking is gone, if it is gone leave it alone if not I'd say start with replacing the first pair of angular bearings. Great video as always! 👍👍

[@RotarySMP]

Glad you enjoy it. That is about my approach as well.

[@GeoffTV2]

Thanks again for another interesting video. Firstly, I will give a +1 upvote for the PR 88. That's the stuff I use and it's great. All the gunge just washes off your hands at the end of the session, just like you said. Secondly, my vote for the bearings is to reassemble what you already have and torque it properly where the screws were loose before. I'm on the fence regarding the bearing glue. I think I probably would use it, but very sparingly. Because it can make future disassembly a real bastard. See what others say, I guess. Hope it works out. - Heather

[@RotarySMP]

Hi Heather, I measured the bearing stack and retainer ring and the preload should be spot on, so I wont use the locktite.

[@comridor]

Super interesting video; I love watching other people take apart their extremely expensive tools. :) If I remember correctly, angular contact bearings generally require some preload to function correctly, so that plate should've been pressing on the top bearing, keeping it from spinning in the first place. Spindle bearings are a specialist thing to be sure, and I can't think those angular contact bearings are affordable to replace, so if it were my machine, and it was still cutting true with no run out on the spindle, I think I'd stick some glue in there to ensure the bearing doesn't continue to spin, and properly torque the cover plate down after checking for potential end play. Belt and suspenders with the glue, but I couldn't see a dab doing any harm, other than taking up any space created by the little bit of spin that's already happened.

[@RotarySMP]

Thanks for your input. I will do a video on my rebuild.

[@lunatic-unicorn]

I love doing things like this. Wenn man sich einfach reinwirft und loslegt, kann man oft sehr viel mehr lernen. So hab ich auch bei meinem oldie mich einfach an die arbeit gemacht, obwohl viele gesagt haben ich soll es lassen. Was soll ich sagen, ich hab so viel über mein auto gelernt. Kann jetzt mit deutlich mehr wissen glänzen und weiß auch wo schwachstellen sind und wie ich sie selbst beheben kann 😊 UND ich kann sagen ich hab nahezu alles selbst gemacht ❤️

[@RotarySMP]

Siehe ich auch so. Ich habe auch überlegt der Spindel wegzusenden, aber Kompliziert ist es nicht.

[@SJDTwo949]

Spindle teardowns, trailer park boys, sailing updates, aviation tidbits... You run a great channel Mark, it has become one of my favorites! Is it possible that the upper bearing spacer rings were spinning? Seems that they wouldn't, but easy to inspect/mic them for wear. If the bearings were loose, they might be too. After full inspection I would relube and put it back together, bearings look ok to me

[@RotarySMP]

Glad you enjoy it. It was pointed out that the loose retainer is a symptom of elongated screws from a plunge crash. I did that crash about 2 years ago, so it all makes sense.

[@jobkneppers]

I think you did find the root problem here. Outer race top bearing spun with spindle. The pre-load cap was loose on 3 screws. Re-lube, remount and pre-load enough to keep the outer race in situ. If the problem reappears you can always do something different like buying new bearings or lock them with glue (not my favorite; it worked for 40 years without it and it disassembled like a dream now. Maybe nice future scenario too.). Best! Job

[@RotarySMP]

Thanks for your input. I still need to strip and inspect the bevel gears bearings, and see if there is another issue as well.

[@jeremylastname873]

I wouldn’t hesitate to use a medium strength thread locking compound on the screw threads. I agree that the bearings should not need adhesive, assuming that the spinning didn’t open clearance. From the looks of it, this was caught before it was too late.

[@joell439]

I also agree with the relube and rebuild plan without the added bearing ‘glue’. My guess is the old grease stopped ‘greasing’ and with the loss of axial preload the outer race wanted to spin. By significantly decreasing the coefficient of friction inside the bearing with new grease, the outer race will stop spinning 😊

[@jobkneppers]

@@jeremylastname873 On the screws I absolutely agree. I ment the bearings themselves. Thank you. Best, Job

[@RotarySMP]

Thanks guys. I am just waiting for some parts like a small torque wrench, lint free wipes etc to reassemble it.

[@steveggca]

Hi Mark At time 11:49 where you look at the spindle schematic I see that the AC bearing are arranged 1 tandem set, and 1 Back to Back ( or O) set. in the comments you mention double O which makes me think 2 BB (O) sets. (Canada,USA and Japan usually refer to the arangements as Tandem ,Face to Face ,and Back to Back). Might want to confirm that. Indeed at 17:29 to 17:33 the second pair are Tandem

[@RotarySMP]

Thanks for checking that Steve. I just got the Maho spindle assembly documentation from a german forum, and that confirms the lower pair are tandem and the upper in O.

[@steveggca]

@@RotarySMP And that supplys a comfortable explanation for why the top bearing might has spun a bit 3 of the bearing are in Tandem while the 4th is all by it's self handling all of the preload , causing a higher rollling resistance another consideration is that with the bearing cap being loose the outter race of all of the bearing would be slightly deform under upward forces.

[@RotarySMP]

@@steveggca At this point I am waiting for lint free wipes and a Torque wrench to continue.

[@steveggca]

@@RotarySMP So there will be a pin wrench to torque wrench adaptor side project?

[@hinz1]

Awesome, Maho vertical head teardown tutorial. Great help, for other dudes, that have Maho spindle troubles.

[@RotarySMP]

Yes, it is something I would have liked to have seen :)

[@jonofalltradesmasterofnone832]

I had my own business doing what you are doing. A a very high quality surface grinder I worked on in the late 80’s the price to replace the 4 bearings was just under £3000.00 then as your time has no cost only time I would loctite the bearings in place and change them if the noise is still there if you have crashed the spindle then the bearing retaining collar is loose then that is most likely cause of the problem, I would also headlock the retaining screws in place and torque up. Great video and takes me back to nearly the same time As your MAHO was built.

[@RotarySMP]

Thanks a lot Jon. Yeah, the crash is on me. I didn't think to retorque those screws at the time.

[@jonofalltradesmasterofnone832]

@ have you got a lower enough torque wrench to do those bolts up if not I will sponsor one for you will find you need one more and more often.

[@Chris-bg8mk]

I'd grease and reassemble. I'd also try to consult Stephan G, and his buddy Alex, both of which are relatively local to you and obviously subject matter experts. Two things that scare me are ultrasonic cleaning bearings, especially unit bearings, where too much power can cause the balls to be bouncing against the races, and gluing bearings, where a tiny bit of excess can get into the wrong places. Love your channel and your AME approach to the machine shop. Cheers!

[@RotarySMP]

Thanks Chris. Since I looked up GE's turbofan bearing cleaning procedures, and they recommend U/S, I have been a bit skeptical of the logical assumption that it destroys bearings. Good point about the adhesive getting where you dont want it.

[@KevinMandy-w8m]

Hey , Keep the videos coming. Love your filming style, logical and steady approach and to top it a fine supply of southing reaggae lol . Well done fella.

[@RotarySMP]

Much appreciated, Kevin. Thanks.

[@vincei4252]

If you've watched this far? I enjoyed every minute of it. I bought a surface grinder about 5 years ago that was bought by some guy in the early 60's. Just one previous owner before me. Have all the documentation, etc. I tried to price replacing the bearings which sound fine to my untrained ear .... I was quoted more than I paid for the entire machine for two bearings 😬 Good to see you found the root cause and there's no major damage.

[@RotarySMP]

Yeah, I think those lower bearings would probably also cost more than I paid for this Maho.

[@theoldstationhand]

After reading through the comments below, I realise you don't need any technical input from me. However, right from the start, the thing that impressed me the most is that you didn't use a rattle gun to remove any fasteners! I often stop watching videos when I see them used - a pet peev of mine. Cheers 👌

[@RotarySMP]

I guess that comes from the RNZAF apprenticeship. Thanks for your kind comment.

[@OddsandEndsMachining]

Great video, thanks for keeping me entertained while I’m stuck at home sick. I loved the suspense as you looked for the problem, hopefully the loose bearing is the culprit.

[@argee55]

Get well soon.

[@RotarySMP]

Hope you are doing better now. Look forward to your next video.

[@dazaspc]

All up it looks decent. The lower roller elements appear to have encountered some sort of contamination with the line around their diameter. Also the burnishing on the inner diameter of the lower bearing shows it has done some work. In a professional production environment it would be replacement time. However as it's a hobby machine in a shed it should be good for years with a relube. The skip of the outer race is definitely the sound heard, particularly low speed. Something had to be skipping to make the noise it did. It can be tricky determining how hard to hold the upper bearings and if it was me I wouldn't be adding any sort of locking compound. Machine brands vary on how they load and retain spindles. Some like Chiron even use quad rings to friction hold the upper radial bearings to prevent rotation Without them its a clearance fit.. 15K rpm spindles held with a bit of rubber and they work reasonably well. The Maho is upside down bearing layout wise compared to most so its a clamped upper bearing. New keeper screws and check the keeper plate for being flat would be all that's needed mechanically.Those screws would have also been stretched from a plunge crash. As they hold the spindle in it's downwards direction. Pretty light duty for a cnc machine especially with a ISO40 taper. However none of this fixes what could be another cause of the problem. If it was me I would also check the acceleration ramps of the spindle motor if possible. On rare occasions this can also cause bearing skip but I don't know if it's in the drive or the control for this machine. Chances are with drives of that vintage it wouldn't be easily adjustable. All up New highest quality screws tightened to their spec torque wise, a re grease including the pinion gear and it will be sweet again. I would say you dodged a bullet with this one. Great Video as usual...

[@RotarySMP]

Excellent input. Seeing as I plunge crashed this machine (on video), stretching those screws is probably on me!!! Thanks for pointing that out. The spindle motor is a dumb 3Ph 3kW, started with a star/delta relay. There is no ramp control beyond that.

[@dazaspc]

@@RotarySMP Sorry I didn't mean to embarrass you. It wasn't my intention.

[@RotarySMP]

@@dazaspc You didn't embarrass me, it was an excellent post, which I found really helpful. I hadn't connected that plunge crash with the screws being loose. I need to take a closer look at those screws, and find some replacements. I did see the scratches in the lower integral bearings, but they will have to go back in as, as replacing them, the spindle and house would be way more than the machine is worth I am afraid.

[@niemanddings9517]

I definetly would recommend watching robert renzettis video on spindle rebuilding, he talks about stuff like not putting precision bearings in ultrasonic cleaners (I think it'll probably be fine), and proper regreasing. I think rebuild is the way to go. That bearing spinning doesn't seem to have caused much damage, and most of it seems to be on the housing, so replacing it won't help much.

[@RotarySMP]

I have seen it a couple of times. Since General electric recommends U/S cleaning of Turbofan bearings, I am fine with it.

[@wimhager]

@@RotarySMP Never put ball bearings in an ultrasonic. I know. Costed me a fortune by ruining a few. The hard surface of the ball hit the hard surface of the ring like a hammer.

[@RotarySMP]

@@wimhager I looked up the turbofan bearing inspections from GE and the clean them in U/S cleaners, but with limits n the power. My little cleaner is no where near that power.

[@wimhager]

@@RotarySMP I would not take the risk. I had to buy new bearings for my Kress spindle. They sound like there was sand in it after a clean in a hobby ultrasone cleaner.

[@RotarySMP]

@@wimhager Where they already damaged? What led you to pull them and clean them?

[@tangomike7]

I'm from 1985 and I'm not 40! You take that back! 😢

[@RotarySMP]

I'll take that back next year okay :)

[@Paddington60]

Thanks for filming and bringing us along! Huummm! What to do . . .

[@RotarySMP]

Hi John, glad you enjoyed it.

[@steventimme5268]

Hi Mark! Enjoyed your show as usual. I would super clean everything, lube it properly, reassemble and make sure you torque everything to spec. Insufficient pre-load can be as damaging or more than excessive pre-load. That bearing does appear to have spun, but not much. It may not be the issue, but looks like that spindle needed some love anyway. It's a pain, but I would reassemble everything and listen with a mechanics stethoscope (or a screwdriver to your ear) on and around the spindle. I can't imagine a bearing spinning would cause that much noise, but the bearing retainer was loose and stuff happens. I would not use retaining compound to secure the bearing unless the scoring in the bore was excessive and only as a stop gap.

[@RotarySMP]

Thanks for your inputs Steven. I still have to strip the bevel gear assemblies and inspect their bearings as well, and will report.

[@samuliranta1101]

Thank you for the very interesting video, there is very few videos on youtube about MAHO spindles and other inner secrets. I have a bit smaller MAHO MH300 manual mill which I have to make some head maintenance in the near future so I really appreciate your effort. Maybe you should add MAHO for your video title so that other MAHO owners can found it easier. 👍

[@RotarySMP]

Thanks for the tip, I added MAHO. My Email address is on the channel page, if you drop me a line, I can send you the Maho procedure for the Spindle, as I got sent it a couple of days ago. It covers all models.

[@milloons2847]

Quite instructive as always. My gut feeling: lube up the bearings correctly and torque the retaining ring to spec. 95% chance this will solve the issue. If not replace the top pair of ac.bearings. Perhaps measure the bearings and spindle for tolerances before reassembly?

[@RotarySMP]

I can measure the bearing OD and spindle with high confidence. The housing and bearing ID less so, as I only have telescoping guages, and µm tolerances are kind f beyond them (and me :)

[@milloons2847]

@@RotarySMP Then ignore the last line in the suggestion. (As from the manual: "Ostridge behaviour for beginners"). :-)

[@RotarySMP]

@@milloons2847 Yep, dont know it, cant hurt me :)

[@MAcDaTHo]

OMG! This is the exact same machine we had in our workshop!

[@RotarySMP]

It i a really nice mill. This one came out of the Handwerkskammer Passau.

[@CalHallows]

I was not expecting to ever see a Trailer Park Boys reference in an engineering video! What a journey deconstructing this, from one noise leads to an intrepid white knuckle dive into the belly of the beast. Hopefully the rebuild bears out.

[@RotarySMP]

Thanks a lot. TPB's is bonkers, but compelling :)

[@MyMiniHomeWorkshop]

My dear old dad was a Motor Mechanic and he used to buy a large bag of Fauldings Barrier Cream and apply that a couple of times a day, I'm guessing it would have been available in NZ as it was in Oz.

[@RotarySMP]

I can't remember the brand I used in the RNZAF, but aircraft mechanics supposedly have the second highest rate of testicular cancer, so they scared us into using it.

[@KallePihlajasaari]

@@RotarySMP Chemical induced cancer was discovered due to the testicular cancer that was common amongst chimney sweep boys who would get creosote in their shorts from the coal fire chimneys they swept and climbed. It seems like excessive skin exposure to various hydrocarbons can be linked to cancer. I think some pure lanolin as a barrier cream might be a safe option for those who do not have access to proprietary products.

[@RotarySMP]

@@KallePihlajasaari Given the phostphate ester based hydraulic oils which aircraft use, it was easy to convince me to use barrier cream all that time.

[@martinchabot_FR]

I love PR 88 because it scent is the same as glue used in pre-school (kleopatra glue). I won't use bearing glue, but definitively medium loctite on the screws.

[@RotarySMP]

Thanks Martin. Yeah, I already made a note to locktite those screws at reassembly.

[@extraace]

I've been dealing a sloppy spindle for years. Took it apart and found the bearings installed backwards and not getting preloaded. It was rebuilt prior to me. 200 for some NOS bearings and I guess luck. I now have .0002" runout. I'm pretty happy.

[@RotarySMP]

Nice save. On mine those bearings in double "O" configuration, and were correctly installed.

[@gorak9000]

wow, where can you find ANY spindle bearings for 200?? My spindle uses 6 bearings (2 back to back stacks of angular contact ball bearings at the bottom, and a set of 2 different size of angular contact ball bearings at the top). A whole set is approaching 1000 at "new old stock" pricing. If I bought them from a bearing supplier directly, probably close to 2k just in bearings!

[@extraace]

@gorak9000 mine only uses 1 set on the bottom (barden 110hdl) and a a sealed ball or roller up top. I didn't have to change the top one. Maybe I got lucky but there were multiple cheap ones in my size on ebay at the time. I just looked and mine were not even 200. $165 off eBay. There are some cheap buys on there right now ($80) if any happen to be your size.

[@RotarySMP]

@@extraace Ebay has a single B71907E-P4-UL advertised as FAG, when the picture clearly shows something else. They are €159 each from Agrolager.de.

[@GBWM_CNC]

You're making great content! Regarding the question - I do enjoy! ;)

[@RotarySMP]

Glad to hear it!

[@Meminsis]

I have done a couple of bearing changes at my workplace, most times on a Reiden BF5 (SK50). We always change all bearing for new ones, because the cost of the new bearings are lower compared to the cost of the downtime and labor of the bearing change. In your case there are probably too expensive to change all, and the shims between the bearings pack have to be adjusted as well, so better keep the old ones. About the gluing of the Outerring, I wouldn't do it, the bearings of the Reiden do have like 0.01mm play when installing. When the locking flange gets tightened, it locks the bearings in the housing. The flange has about 0.05-0.1mm air to preload the Outerring in the housing. Please control if you're clamping flange for the Outerring as a little of preload (0.05-0.1mm) to hold the Outerrings in place.

[@RotarySMP]

Thanks a lot for your input on this. My shed is a retirement village for these machines. Downtime is irrelevant, and they get used for a few hours a year. I appreciate that you took the time to give me your experience.

[@TheDistur]

I can't afford this problem so I'll leave it to the experts. Thanks for sharing the process!

[@RotarySMP]

Thanks for commenting.

[@Hilmi12]

Back when I used to work on an oil rig never new about barrier creams. Wish I knew about it back then

[@RotarySMP]

It was a novelty back when I did my apprenticeship. Some MLM started selling it into the RNZAF. Glad I started using it.

[@Hilmi12]

We got exposed to all kinds of gunk, especially when drilling with oil based mud

[@RotarySMP]

@@Hilmi12 I bet. The oil is bad enough, but the additives can be really toxic. The aerodynamic sealant used on plane Pro-Seal PR1422, had strontium in it's catalyst back when I did my apprenticeship.

[@jdmorgan82]

You know what, I’ll just go ahead and share your videos with all of my friends at DMG Mori. See if I can get you some interesting fans.

[@RotarySMP]

Thanks a lot JD. It they want to sponser the channel, I am open to that :)

[@ChimeraActual]

I notice that MAHO is a bit more complex than my 1958 Bridgeport M head... But like you I need to do a spindle rebuild soon.

[@RotarySMP]

Go for it. A stitch in time...

[@ArcAiN6]

Reassemble and properly torgue down the bearing preload ring. Test run the spindle listening for the rattle again (replace all 4 pairs of the upper bearing) check for excessive heat (over tight ring). At the end of the day, it's best to just replace the four bearings, be sure to get matched sets (they will usually be marked)

[@RotarySMP]

Thanks for you input.

[@subuser9627]

I like the details. I would check all the possibilities and the prices of the parts before making a choice what to do.

[@RotarySMP]

Thanks. The upper bearings are €150 each (or €300 each depending how many letters you want in the model name)

[@belatoth3763]

These investigation videos are the most interesting ones for me. Like Curtis with the jig borer. I'm not this happy when it happens to me of course :)

[@RotarySMP]

Thanks, yeah, it is nice to watch another doing it :)

[@JaapGrootveld]

I would not glue the bearings. I think they need a bit of play. The inside of the spindle gets hotter than the outside. I would definitely replace the top bearing. Some spindles need oil, check the book carefully. Only use the correct grease or oil. And with grease it is important to use the correct amount. Too much can cause overheating at high revolutions.

[@RotarySMP]

Thanks Jaap. I also decided not to glue them in. I got the Schaeffler spuer precision bearing catalog (they bought FAG), and it has the grease amount for these bearings (I calculated 1.1ml, but the specify 0.64ml) and the break in procedure in it.

[@jonofalltradesmasterofnone832]

I had my own business doing what you are doing. A a very high quality surface grinder I worked on in the late 80’s the price to replace the 4 bearings was just under £3000.00 then as your time has no cost only time I would loctite the bearings in place and change them if the noise is still there if you have crashed the spindle then the bearing retaining collar is loose then that is most likely cause of the problem, I would also headlock the retaining screws in place and torque up.

[@RotarySMP]

Thanks Jon. I get it. A company sending a spindle to a rebuilder needs a fast turn around and a warranty. I have different needs, as this not a production machine, and I only run it about 20-50 H per year. so down time is irrelevant. It is also easy enough for me to pull the spindle out again. I will lube and regrease and see if I get a couple more years out of those bearings, but at the same time I will try to source replacement rollers for the integral bearing, and use the current set up to machine up some cages to make up a replacement set. Then replace the B71907's and integral bearings at the same time. I have measured the stack up, and the retainer preload is in spec, so glue will not be needed.

[@MF175mp]

I would've checked if it still rattles after removing the drawbar system. Just to avoid any unnecessary dismantling.

[@RotarySMP]

The bearings needed inspection and relubrication anyway after 40 years.

[@MF175mp]

@RotarySMP also I would think the preload in the angular contact bearings is ground in, so you just sandwich them together and the preload won't be affected by the tightness of the nut. That's how they usually are, could be some different ones though

[@RotarySMP]

@@MF175mp You are right. I was sent the MAHO bearing adjustment procedure, and it is ground in.

[@briantaylor9266]

I'm just a simple civil engineer, but I'll cast my $0.02 worth anyway. I would lube and reassemble and see if you've fixed it. If the rattle is still there, replace the top bearing. If that fixes it, pull out those socket head cap screws (that were initially loose) and reinstall with some blue Loctite. If replacing the bearing doesn't fix it, get advice from someone that knows more than a civil engineer. 14:48 Always fun to see the Trailer Park Boys. The actors are local to where I live, and one of them is a friend. For the record, they are nothing like the characters that they portray. 20:54 Electric tooth brush for parts cleaning! Super idea! I'm going to steal that idea.

[@RotarySMP]

Trailer park boys was a bonkers series. I bet they had a hilarious time on the set, as I read a lot of it was improvised. Thanks for your Inputs Brian. You the difference between civil engineers and mechancial engineers... They build weapons, you build targets :)

[@inmyshedwithbc.]

A jar inside the ultrasonic cleaner will be my go to for annular cutters. Great idea. I had a similar noise with my First mill and it was spline rattle. Some oil was a quick cure. BC

[@RotarySMP]

Thanks for the input on that. I will be lubing up the spline during reassembly too.

[@pgbcredneck]

I'm in western canada, and we use pr88 at work.

[@RotarySMP]

Good one. It works well, the grime just falls of with a bit of soap.

[@Zertrebender]

Hi Mark, I've worked some time in Spindle construction in Germany for a big Lathe company, i wold highly recommend replacing all bearings, at least the 4 Angular contact. They are really brittle and like to run in even if they stand still with no load, it's called false brinneling and an ultrasonic cleaner surely ruined them in my opinion The markings you've guessed correct, they are all matched pairs because back then and still tody the tolerancees are too tight to get a proper seat without matching different measurements together. In my company at least there was a no new bearing after disassembly protocol, even if I put a spindle together and messed up. Once they are run in and gone through a (idk the name in English in German it's Fettverteilungslauf) we replaced them always. Even if you lube them make sure to do at least 2 cycles of the mentioned "Fettverteilungslauf" because you need to spin the Lubricant out of the races and push it arround so that it releases oil slowly. If you do that Monitor the temperature and if it climbs over 60°C (it will trust me) let it cool down and start it again. Do this so often untill the last step of the "Fettverteilungslauf" doesn't increase the temp any more and your spindle should be good to go for the next 10-20 years

[@RotarySMP]

Thanks a lot. I need to measure the rollers and see if I can source a replacement set. Remember your company needs to warranty your work. I only run this mill about 20-50H a year, have no production pressure, and can easily tear the spindle down again. So for now I will clean and relube them and set up to replace all four B71907 plus the integral bearing rollers when I pull them back out. The Schaeffer catalog has the correct grease amount, and also the recommended run in procedure in it which is handy.

[@Zertrebender]

@RotarySMP oh then I would try to go with the old ones and keep an open Ear, i didn't realize that you only put on so few hours a year, normally I see them as great workhorses since I've worked on one for about 6months in which this machine ran for nearly 15h/day rughing CK45

[@theromihs]

I think that simply torquing the top outer races will be sufficient to sort out your issues. It certainly all looks really good..

[@RotarySMP]

Thanks a lot.

[@neffk]

You might want to use some Fluid Film or LPS3 on the machine surfaces when you re-assemble. I'm in NC and I get rust spots if I don't take special care. Your shop is probably not as humid but temperature extremes can produce condensation. RE the rebuild: I would not replace any of the bearings---just set the pre-load correctly. You found the smoking gun. BTW, find the marks on those pairs of bearings so they're clocked correctly. Also, the spacer orientation should be set up to cancel out any out-of-parallel condition. ROBRENZ has a good video on the topic.

[@RotarySMP]

It looks like Maho put a very even coating of the bearing grease throughout all the metal surfaces. Probably to avoid contamination from a different product like LPS3. I forgot to video the bearing markings, I'll put that in the reassembly video. Thanks for the reminder.

[@thieltech1]

Reassemble old bearings with new grease. Careful with the bearing retention lock tite. Some manufacturers want only lite oil on races. As there's very slight bearing expansion once they warm up. Just some thoughts

[@RotarySMP]

Thanks for your inputs.

[@JonathanSteinert]

With respect, and sadly for time spent... I think you need to continue the root cause search because there may be more problems still to be found in the gearing. Put bluntly you can't stop searching for the problems just because you found the first one. If possible you should run parts of the machine as smaller systems to see if you get the sound in isolation. The easiest thing at this point might be to mount the head back on and run it without the quill and drawbar installed and see if it makes the sound by itself. I am not a machinographer or machinologist but I really think that sound came from somewhere else because the bearing that has the marks is supported by the other 3 in the stack, and is far from the forces applied to the spindle. I don't think a knock sound can come from it spinning. Maybe Robrenz will leave a comment with some insight. :)

[@RotarySMP]

Good point Jonathon. Stripping the bevel gearboxes for inspection and relubrication of their bearings is my plane for this week. I can't really run a partial units, as the gripper is loose in the spindle (not sure how that is removed?) Good idea to run only the bevel gearbox alone though. Thanks for your inputs.

[@JonathanSteinert]

@@RotarySMP Best of luck on this hunt. I always love seeing you use this machine because of how large it compared to the room you keep it. I don't want it to have problems :)

[@RotarySMP]

@@JonathanSteinert It is a very low ceiling :)

[@alan-sk7ky]

Depends on how much the top bearings are to replace Mark, if arm/leg replace the top one only. if reasonable all 4. I use a product called 'Derma Shield' it's foam in a can, as far as I know it's a PVA glue layer that's formed, lasts for ages dries to nothing withstands light washing too which is nice for doing the clean work after the dirty bit 🙂

[@RotarySMP]

About €150 each bearing Alan. Oh right, Dermashield, that is the one we used in the Air Force.

[@Koptokaf]

Lube and reassemble the spindle, torquing everything appropriately will fix the rattle. I would not use retaining compound on the spun bearing since it could cause more problems than it solves. Either of the 3 options you laid out would fix your issue, but option 1 is the obvious choice as I see it. 2 and 3 are unnecessary :) Love the "mechanical detective" videos, despite the painful (for you) cause for their creation.

[@RotarySMP]

Thanks for your feedback. I appreciate it.

[@argee55]

Really enjoy your videos, even if the majority of them are well over my masochistic head.

[@RotarySMP]

THanks for the kind feedback :)

[@theinfernalcraftsman]

I have that PR88 in my list now. There used to be stuff here like it called invisible gloves that I would buy that worked the same way. I do go through allot of nitrile gloves and I got lucky and bought a few cases of them for $10 a case post pandamonium as they were donated to Habitat for Humanity which builds houses for people in need and has a resale store for stuff they don't use. The wear isn't bad at all and I have seen far worse on fairly low use bearings on various stuff. Looks like what happened was the screws loosened up over time and allowed that upper bearing to spin since it is a slip fit to start with. I would regrease and reasemble but I would use blue locktite on those locking screws. If that top bearing seems to have any internal damage I would look into replacing it however I doubt that is the case. It just spun because it had the opportunity to not because it was a bad bearing. If the top bearing isn't too expensive I'd say go ahead and replace it but usually those bearings are quite pricey. In short I'm not too worried about what I see there and would have no problem greasing it up put it together and see what happens. I don't know how many people know what a labyrinth seal is though. But thinking about it... Machine builders could add them with a built in blower to keep dust and chips out of bearings and other areas.

[@RotarySMP]

Hi Robert, It was pointed out that the loose retainer is a symptom of elongated screws from a plunge crash. I did that crash about 2 years ago, so it all makes sense. I will sources replacements of those screws which stretched. It is clear that Maho left a much deeper turning mark on the portion of the spindle which acts as the labyrinth seal. I don't know what the rotor/stator clearance is there, but suspect it is minimal.

[@theinfernalcraftsman]

@@RotarySMP Ahh. Makes perfect sense. Now i'm thinking either leave it as is and know that is the weak link on the next crash and to replace those screws or make a heavier plate and stronger screws etc. IMO leave it as is and if you crash it again just know to replace those screws.

[@RotarySMP]

@@theinfernalcraftsman Yep, I will just inspect the retainer for distortion, but reuse it if okay.

[@melgross]

A conundrum. If the manufacturer didn’t use Locktight or some other bearing lock compound, it means that they expected the fit to be sufficient. If you find that’s not the case, then it’s a bit worn. If you do choose to use the locktight, then assemble before it hardens so,that it will align properly. But as someone else suggested, check the spline. The spline on my mill gives a rattle at some speeds, that’s not a precision fit and as it ages the pinion and gear around it become a bit battered and the fit gets worse.

[@RotarySMP]

I will probably avoid the adhesive, and check the preload of the outer races is correct.

[@arnonuehm2]

Maybe another thought, maybe other people have said it before: Could you measure the quill ID where the top bearings ran to see if there is any actual wear there? Also, maybe try to run the top bearing on its own with a bit of a load on it to see if it makes noises on its own. Another thing: Maybe also take the drawbar apart to check it since it's off the head now anyway. Other than that, I'd just relube, (deburr where necessary,) reassemble and hope for the best! ;-)

[@RotarySMP]

I can measure ODs to µm, but am not tooled up with the sort of decent internal micrometers to reliably measure bores to µm. Next I will strip the angle gearing bearings and inspect/relube them.

[@EZ_shop]

Repack and reassemble. Ciao, Marco.

[@RotarySMP]

Thanks Marco.

[@johnspathonis1078]

Hi Like you, I would want some sort of barrier on the bottom end to stop coolant etc from entering the spindle. Would it be possible to fit a PTFE O-ring in that bottom end. PTFE is soft and will conform when compressed and adapt to the space available.. Hopefully it will present a barrier by virtue of very close running surfaces. Cheers

[@RotarySMP]

You can't fit a contact seal in a spindle, as it will just overheat. I think it is a pretty effective labyrinth seal in there, using only a very narrow gap with a serrated surface finish. No much has gotten up to the that integral bearing.

[@johnspathonis1078]

@@RotarySMP I am all for trying new things. I always think --- What is the worst that can happen? If the rpm was 4000 and spindle diameter is 50 mm then the surface speed is about 10,5 m/s If you look up the allowable surface speeds of commercial PTFE seals a number of seals exceed this value by a factor of 3 or 4. A smear of MoS2 grease at assembly will help also. If the pressure on the seal is too high, it will wear and reduce the surface pressure to where it is comfortable (self regulate). Select a oring diameter where there is only a small amount of crush. It is just a sugestion for consideration. Cheers

[@gorak9000]

wow, unexpected Trailer Park Boys. Canada Represent!

[@RotarySMP]

Glad you recognised it. What a bonkers show :)

[@gorak9000]

@@RotarySMP Me and my dad used to watch it religiously every week when it was on TV, in Canada - back before downloading and streaming were popular!

[@RotarySMP]

@@gorak9000 I can't believe that was on tele :) I googled the cast, and Lucy is an Air Force officer. Hilarious :)

[@chrismayer8990]

I would first grease it again and put it back together. It's relatively easy to take apart. If necessary, you'll have to do it again. (More content for KZbin!) 😉 One question: Why does the ultrasonic cleaner work so well for you? I also have one, but I'm usually better off cleaning parts manually. I'm surprised that it works through the glass anyway.

[@RotarySMP]

Hi Chris. Yeah, that is the advantage of a machine not in production. Downtime doesn't matter. I had those bearings in white spirits (petrol), and the grease was still soft so it probably would have dissolved off even without the U/S. When I did the dirty band saw components a few weeks ago, I used a citric acid based solvent. On a whole I am pretty happy with that U/S bath. I killed it's heater pretty fast (by turning it on with an empty bath), but it works pretty well.

[@Goguleroma]

Personally, i would remout the spindle as it is, mark the bearings positions, do some tests and check for bearing spin, if they spin, buy a +0.01 /+0.005 oversize bearing or glue them if the cost if way too big, although, i feel a test is needed. Btw, go want the Robin spindle rebuild video, it is a gem of knowledge .

[@RotarySMP]

I have seen it before but need to rewatch it.

[@andrewbird3691]

I wonder if when the angular contact bearings are preloaded correctly they expand slightly to fit the housing.

[@RotarySMP]

The preload on these is light (the L in the UL designation), so they probably dont. The axial preload should lock them.

[@jameshisself7375]

Since you found witness marks and a fault in the loose preload bolts, I'd reassemble and re-grease with all original parts. Check the torque value for the preload bolts and set or maybe even add loctite. Test further.

[@RotarySMP]

Thanks for input on this James.

[@audigozer]

Throw it back together, maho’s suppose to rattle, let it dig some metal, it’ll like that. Nice vid, good cleaning, you dont need advice from anyone 👌

[@RotarySMP]

Thanks for your kind feedback.

[@mp6756]

I have only used a locktite bearing retanung compound once before with a great result. However, it wasn't on an angular contact bearing set or pairs. The nature of a contact bearing sets in pairs with proper axial load wouldn't allow the outer race to rotate. In my humble opinion, the problem was the obvious one the retention ring bolts were loose. Im confident once you torque the bolts properly, the problem will be solved. It's fortunate you didn't put off the service. Otherwise, you probably would be shopping for a new qwill. Im a bit jealous of the condition of the machine. it's a fine example.

[@RotarySMP]

Thanks a lot. Yeah, I am glad I provrastinated by working on the Doall, rather than putting on head phones and ignoring the mills noise. Another commenter pointed out that those screws elongating would be a symptom of a plunge crash. Since I plunge crashed this machine a couple of years ago, that makes sense. I will source replacement screws.

[@JaapGrootveld]

Are you shure the wole thing has to have grease?

[@RotarySMP]

It does. Used to be Kluber F23A, which is now NBU 15. I got sent the Maho Spindle bearing replacement procedure yesterday.

[@kusler67]

I enjoyed it AND I'm a masochist!

[@RotarySMP]

Thanks for your comment :)

[@TheDayzman]

Schwere frage am ende... Da du einen behebbaren fehler gefunden hast und die lager vermutlich nicht günstig sein werden option 1. wenn dann noch probleme auftreten ein kleiner tropfen kleber auf das oberste lager im zusammengebauten zustand. Ich hab schon mal ne spindel versaut mit halbhertzigen reperatur versuchen. Viel erfolg beim wiederzusammen bauen

[@RotarySMP]

Danke für dein Inputs. Ich hoffe keinen Schaden zuzuführen.

[@marcg2233]

with new bearings ranging from 150$-550$ if they spin fine cleaned up. I'd just repack them and test to see if that solves it. however i can see the case for replacing the one that spun if that puts your mind at ease. replacing all of them could get pricey. I guess it, depends on how long it took you to undo the whole thing seemed like 20 min for us but could have been days for you.

[@RotarySMP]

Now I know how to do it, it will go even faster next time. And this is only a hobby machine, so downtime is not an issue.

[@andypughtube]

There are still bearings and rotating parts that have not been inspected, specifically the rotating parts in the bevel drive system. I don't think that we have even seen the arrangement that the driven bevel rotates in? It seems like it was time to clean and re-lube the bearings anyway.

[@RotarySMP]

Hi Andy, Correct, those angle gearbox bearing inspection and relube is my task for this week :) It was pointed out that the loose retainer is a symptom of elongated screws from a plunge crash. I did that crash about 2 years ago, so it all makes sense. I will sources replacements of those screws which stretched.

[@Narwaro]

Its very interesting to see how the Maho machines are functionally extremely similar to Deckel machines of the same era, although they didnt merge until about a decade after.

[@RotarySMP]

I guess there was probably a far bit of incest in an industry like that, which people and ideas switching. Aviation is like that.

[@Neudezign]

😂 "you're either enjoying this or you're a masochist..." mmmm... a little of column A and a little of column B 😊 definitely enjoy your videos 👍✌️

[@RotarySMP]

Thanks for your kind feedback.

[@Johannes58934]

23:23 That looks like a mess looking for a place to happen... Getting it off when the issue persists? I'm one that leans toward new bearings. That top bearing could be starting to bind up with unseen kaka causing the noise... 40 year old sealed bearings screaming to be switched out? We're right in the middle of fine German made bearings!

[@RotarySMP]

Thanks for your input on this Johannes. My concern is if those bearings got selected into matched sets by Maho, and I cant reproduce the preloads.

[@timeckelmann1196]

Relube and reassemble

[@RotarySMP]

Thanks for your input Tim.

[@JAMESHOPKINSIBXCNC]

I haven’t even finished the video yet and immediately I see spline drive on the spindle. There’s you clanking noises!! Mine did it until I belt drives it and made a nylon bushing to lock the drive and the spindle.

[@RotarySMP]

Thanks James. No way will this get a belt drive. There is an 18 speed gearbox under CNC control there. I am not giving that up ;)

[@squelchstuff]

I'm in the regrease, rebuild, and skip using bearing glue camp. That retainer plate being loose is definitely a suspect as that is what holds the outer races of the stack and prevents spin out, so replace the fasteners and torque down properly. I'm not seeing anything else of concern on a low duty machine, but it's worth a follow up inspection after another few (say 50) hours of run time. A periodic audio recording top and bottom of the head using a stethoscope or contact microphone might be prudent as that can reveal any significant changes over time. Of course, the rest of the drive chain needs to be checked too, but the regular intermittent wear pattern around the top race housing tells me that that is the the source of the noise at certain speeds. Good luck.

[@RotarySMP]

Thanks for that. There was a. comment that the retainer screw stretching is a sign of a plunge crash, which reminds me that I did that a couple of years ago. So I will be sourcing new screws.

[@squelchstuff]

@@RotarySMP It was @dazaspc's comment that prompted me to suggest the fastener replacement, but I was remiss in giving attribution. I do remember wincing at the crash and marring the table.

[@RotarySMP]

@@squelchstuff Yeah, I have ordered new screws and a small torque wrench. I got sent the Maho spindle replacement procedure, and those screws on get 3Nm.

[@johnlemmey7698]

I would assemble dry and measure the play on the angel contact bearings. Grind spacer rings to remove excessive play. either loctite or electroplate quill to give interference.

[@RotarySMP]

Thanks John, Another commenter pointed out that those screws elongating would be a symptom of a plunge crash. Since i plunge crashed this machine a couple of years ago, that makes sense. I will source replacement screws. I will measure the stack up.

[@Spiderelectron]

Am I the only person left in the world who remembers having it taught to me in my early days of engineering (1970's) the difference in pronunciation between Greece (the country) and Grease (the lubricating stuff). I was taught to say grease kinda like "greeze" (like the word Ease). I guess it doesn't matter anymore, the English language is ever evolving.

[@RotarySMP]

Grease the noun, to "greeze", the verb. At least that is the way I learn it in NZ.

[@DieterTheHorst]

Guess I get to eat my words on the split cage. As for the angular contact bearings, if the one that spun shows no damage, they're likely fine to reuse, if you can get them tight with the retainer plate. Better to skip the retaining compound if at all possible, once glued in place, they'll be a nightmare to remove again, and using heat to release the compound is prone to damage the phenolic cages on the whole stack. I'm not personally familiar with the Maho specs, but if you decide to go the route of replacing any of the four, it would be prudent to check if the stack is supposed to be matched (as four or as two pairs) or not.

[@RotarySMP]

Thanks Dieter, that is what I dont know, whether MAHO took these universal UL bearings and matched up sets with their spacers or they are really universal. Another commenter pointed out that those screws elongating would be a symptom of a plunge crash. Since I plunge crashed this machine a couple of years ago, that makes sense. I will source replacement screws.

[@santeritoikka]

I would comment on a video to show support on a good channel and suggest measuring all the surfaces to find out if there are discrepancies.

[@RotarySMP]

Thanks for the comment.

[@Alberto-rn7vi]

My vote would be for option 1 and maybe using some bearing glue on the top bearings. Nothing looks damaged or out of spec but then again im an automotive tech and not a machine tool one Cheers from Cologne

[@RotarySMP]

Thanks for sour input Alberto.

[@TimDousset]

I reckon lube and re-assemble, but maybe some blue loctite on the spindle cartridge screws that came loose.

[@RotarySMP]

Thanks for your feedback Tim.

[@haydenc2742]

I'm unqualified to reply... I would re-grease, then on those caged bearings put a single drop of that retaining compound on the outer race..only problem is...next time you have to go in...might need a puller...just make dang sure you get everything re-torqued back to specs... Those fancy looking roller bearings probably cost an arm and a leg to replace...never seen anything like that made with brass! So very cool that it came apart so nicely...does the bevel gears inside have grease or oil in them...might need to open the main housing and see if the bevel gears need cleaning and re-lubricating...since you are that deep into it already

[@RotarySMP]

Thanks Hayden, the bevel gears have a grease nipple. I will pull the gears bearings and inspect and regrease though.

[@paulbyerlee2529]

Is it possible the bearings are meant to allow for a little float. I'm guessing the 4 at the top locates the spindle in the axial direction and the bottom takes the radial loads. Ps im a masochist😂

[@RotarySMP]

I think you are right Paul.

[@stevenrichardson7882]

Before taking the spindle out you could have made an adapter to connect to a drill and run it, that way you would know if the noise is generated by the spindle bearing or not?

[@RotarySMP]

True, that could have helped. Thanks for the suggestion Steven.

[@wiju]

With those p4 bearings you have to be very cautious when there is no grease in them, even littlest bumps are then able to mark the bearing races.....

[@RotarySMP]

Thanks. Given that the white spirits only desolved the old grease, they are not completely dry, as they would be if I had used NaOH bases solvent.

[@johnhawkinson]

As person who strongly desires diagnostic certainty my path would be: Maybe try to measure the stretch of the loose screws (make up some thread fit gauges? Tap holes with a range of undersized tap drills?) and replace them regardless (cf. plunge crash comments). I would, as a first step, reassemble with the new screws torqued down and minimal-but-necessary lube (whatever that means) and check for the sound. Possibly, if one lives dangerously, then disassemble, loosen them (put back original stretched ones?), and see if the sound returns. Then you have more diagnostic certainty. And if so, disassemble, lube properly, reassemble with new fasteners (maybe loctite? maybe not?) and done. Of course every disassembly/reassembly cycle takes a lot of time, but the certainty of knowing you've found the original problem is worth something. I would not loctite on initial assembly, only after verifying the problem is resolved.

[@RotarySMP]

I am not patient enough for that approach, although it is a good one. I will still strip the angle gearbox and inspect and lube those bearings though.

[@Teklectic]

I think you found it, no preload on the upper bearings, sticky, old grease and one spun bearing at high speed. I'd relube, reassemble, use a little blue Loctite on those preload screws, cross my fingers and test it out!

[@RotarySMP]

Thanks for you input on this.

[@billgilbride7972]

I side with lube reassemble w bearing glue on outer race and see if tightening the loose bearing tension screws eliminated the noise. Maybe you caught it early enough. 40 years between lube maintenance is pretty impressive.

[@RotarySMP]

Thanks Bill, I was also pretty impressed how well the lube had worked. Kluber is expensive but they make good grease.

[@mudnducs]

You know how to disassemble now. I’d reassemble with a fully torqued upper bearing retainer /preload plate and new grease. Run it and watch.

[@RotarySMP]

I am tending that way. Thanks.

[@ronniejarvis2679]

Relube, reassemble, and go from there. Possible consider using 222ms or 242 loctite on the 6 loose screws. I believe that you caught the issue in time to only have very superficial witness marks. Retaining compound always scares me for A. Always a possibility of the compound migrating where you don’t want it and B. Future disassembly.

[@RotarySMP]

Thanks Ronnie, I see it like that as well. It was pointed out that the loose retainer is a symptom of elongated screws from a plunge crash. I did that crash about 2 years ago, so it all makes sense. I will sources replacements of those screws which stretched

[@joshuahuman1]

good video I would avoid cleaning cleaning those bearings with an ultrasonic cleaner. It was probably fine for the roller bearings but might cause issues for the rear bearings. The ultrasonic cleaner causes vibrations that can cause flat spots to form on the bearing race or bearing balls.

[@RotarySMP]

Thanks Joshua, that is logical, but I checked the overhaul manual of a gas turbine, and they U/S clean the bearings with way more energy than my like import cleaner could exert.

[@heronguarezi6501]

There are 2 more bearings in the head. Good idea to inspect those to

[@RotarySMP]

True I need to finish the inspection of all four, and also strip the angle gearbox and inspect the four bearings in there as well.

[@donkultgen4643]

What's the cost and wait for new bearings? Are they $40 or $400 each? Not knowing that, I vote option 1 + retaining compound. Run it without the drawbar as well.

[@RotarySMP]

Probably at least €150 each. What I dont know is whether Maho did any matching of bearing sets and spacers.

[@RotarySMP]

The top ones are €159 or €269 each, depending if you want a T in the model number or not.

[@donkultgen4643]

@@RotarySMP if it were me I'd buy 1 at 159eur and run it. I'll wait for the video to see your choice.

[@mgnbukint6502]

I would expect that those angular contact bearings are supplied as matched pairs, with the inner & outer spacers being the same thickness to make the assembled bearing stack stand just proud of the recess so that the clamp plate holds the outers securely against rotation. I would not use a bearing retaining compound here, just check that the bearing outers stand clear of the top face for the clamp plate to do it's job when properly tightened. The matched pair bearings are supplied such that the required preload is "ground in" & the spindle locknut should be done up tight. Important not to over grease these - recommended IIRC is 40-50% of the free space within the bearing. Bridgeport in the UK used to weigh out Kluber NBU15 in syringes & apply the grease evenly within the bearings for their CNC spindle cartridge assemblies (assembled under clean room conditions - they had a special area for this operation) , then run them in on a test rig. Kluber called the running in process "breaking down" the grease, and for high speed spindles it is done in stages and can take many hours. Start by running at a low speed (100-ish rpm) for 20 mins / half an hour. Check tenperature. If cool, increase speed by a couple of hundred rpm & repeat. If warm (40 deg. C-ish), allow to fully cool to ambient and repeat the run at the same speed as before. At a previous employment we used to overhaul high speed heads running 12K rpm & these could take 2 or 3 days to run in. Last machine I replaced the bearings on (Cincinatti Sabre 2000) took a couple of days to get to 9K rpm. Too much grease or trying to run in too fast can result in a hot running spindle and, with a quill as you have, a seizing quill after running at higher speeds due to expansion. Only cure for a hot running spindle was to strip it, clean out the grease, re-grease more sparingly and retry the running in. I understand that ultrasonic cleaning of assembled rolling element bearings is a no-no - causes brinelling damage to both balls and raceways that will show as nosiy running and, ultimately, surface failures of both due to impact damage. For large spindle bearings that were difficult to get hold of, we used to have bearings refurbished - dismantled, races reground & re-assembled with oversize balls - but the overridding factor that determined if a bearing could be re-furbished was evidence of brinelling or pitting in the races, as these would be the source of faliure as they signified that the race surface was breaking up. For the investment of a bit of grease & your time I would try putting it back together using the original components before taking out a second mortgage on a set of replacement AC bearings. You might get lucky ! If you turn out not to be lucky and have to buy the bearings after this you are not much worse off than before. Nigel B.

[@RotarySMP]

Thanks a lot for sharing your experience Nigel. These are UL universal light, rather than matched sets. I have measured the stack and the retaining plate and the stackup falls right in tolerance. I was sent Schaeffler (who bought FAG) precision catalog link, and they specify the run in routine, and also specifies the grease amount for this beaing. I had calculated on 25%, and came up with 1ml, but Schaeffler says 0.64ml. I have NBU 15 and just went to the pharmacy for a syringe. I am waiting for the ordered lint from wipes and small torque wrench to arrive before proceeding. I have downloaded the RR and GE turbofan bearing cleaning standard practices, and both allow U/S cleaning for assembled bearings with time and power limits (I am pretty sure my model is well below those power densities. I see it the same way. This Mill is in a retirement village for old CNC's (my basement) and will probably run 20-50H/year. I have no time pressure so if I found the bearings are ruined, I will just do it again with new bearings, and then also source some new rollers, de-rivet the cages and replace the rollers at the bottom.

[@mgnbukint6502]

@@RotarySMP "also source some new rollers, de-rivet the cages and replace the rollers at the bottom." Good luck with that ! What size rollers would you be on the look-out for ? Given that the housing / spindle were apparently graded in low single digit micron deviations from nominal , you would want rollers sized with similar accuracy to get the required running fit - which is what ? And from conversations with a Timken applications engineer WRT to precison crossed roller bearings for a VTL table, rollers matched to 1 micron within the bearing to get the running accuracy. "General pupose" rollers (if you can find someone who stocks them) would be graded in much coarser bands than I would expect to be used here, so you would be looking at buying a lot of rollers and grading them yourself. Trying to get (by the looks of it ) 40-odd rollers within a particular size range for the "correct" clearance and matched within a tighter range for running accuracy would be some undertaking for a home workshop. Whether or not you "need" the original standards of accuarcy for a home shop machine is another matter - what is that adage about "letting perfect be the enemy of good enough" ? Looking forward to seeing how you get on. Nigel B.

[@RotarySMP]

Hi Nigel, I see what you mean. The rollers are all within a µm in diameter within a bearing. I measured up the rollers and one bearing they are all diameter 5.000 x 4.994 long, and the other they are 4.998 x4.99 (there is more spread from 4.991 through 4.998 in length on that one. 22 rollers per bearing. Cheers, Mark

[@mgnbukint6502]

@@RotarySMP Hi Mark, Interesting. Did you mark the bearings on dis-assembly to know where the larger diameter roller equipped cage was located on the spindle ? I wonder if the difference in roller diameter is deliberate and maybe a method by which heat generation in the bearing was minimised. It does not take much heating of a precision fitted quill to cause it to jam up, so heat control is important. If only one bearing is to a tighter running fit in an unloaded state, less bearing contact area & thus less heat build-up, particularly at higher speeds. At higher loads, distortion / defelection of the closer running fit bearing would lead to the second bearing coming into play to add additional support. In that scenario, maybe makes sense to have the closer fit cage assembly nearer the business end of the spindle, with the slacker fit cage inboard of it ? I would be even more inclined to just sparingly lubricate and re-assemble what you have in the order it came apart to see how it goes. There seems to be some high precision and subtlety there that should not be easily dismissed. Regards, Nigel B.

[@RotarySMP]

@@mgnbukint6502 Hi Nigel, Yes, you nailed it. There is discoloration on the cage of the one with the larger rollers, and it is the lower position. That is also my intention. I measure the upper bearing grouo stack up and there is 0.02mm preload on them with that retainer cap, which seems spot on for the design.

[@vaderdudenator1]

My vote is for Relube, reassemble with original bearings and some bearing retainer.

[@RotarySMP]

Thanks for your input.

[@mog5858]

I would go with #1. to me you need to be looking at the bevel gears. it sounded loud when you spun it by hand and you really haven't found much wrong in the spindle. I would say the outer bearing might be creep and not a full spin. the lock-tight might not be good as things heat up and try to grow in length.

[@RotarySMP]

I will strip, inspect and relube the bevel gear bearings next. It was pointed out that the loose retainer is a symptom of elongated screws from a plunge crash. I did that crash about 2 years ago, so it all makes sense. I will sources replacements of those screws which stretched

[@Spirit532]

I was going to suggest to regrease and reassemble, but unfortunately you basically guaranteed that the upper 4-bearing stack needs to be entirely replaced by putting them into the ultrasonic cleaner. The ultrasonic cleaner causes very frequent high impact collisions to happen when there's metal surfaces in contact, causing damage to the balls and races. There are some industries that say they're fine, I'm sure one of which you're very familiar with, but I've rebuilt high speed turbomachinery(of the vacuum variety instead of power) and I can say, from personal experience(for whatever that's worth), that ultrasonic cleaners do damage bearings. If I remember this comment when I am back near an SEM, I will throw a bearing in the ultrasonic and show the resulting microscopic carnage.

[@RotarySMP]

If you could send me that footage, I would be happy to include it in my next video (and credit you for it). A before and after on the SEM would be excellent. I find it weird that GE and RR both allow it then.

[@Spirit532]

@@RotarySMP Sure thing! Will put something on my calendar to remind myself.

[@RotarySMP]

@@Spirit532 Just for planning, any rough idea when that would be, please? My Email address is on the channel front page.

[@Spirit532]

@@RotarySMP Sent you an email.

[@RotarySMP]

@@Spirit532 Thanks.