Hints on Spindle Bearing Adjustment
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- čas přidán 20. 07. 2024
- Some Hints on the theory and practice of adjusted bearing arrangements, or adjusted bearing spindles. With emphasis on preload determination and some practical aspects of setting a particular preload. The spindle in the video is my newly designed and built, highly flexible and compact welding positioner (rotary welding table).
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Having rebuilt more precision spindles than I really care to think about (retired now) in my working life this is an excellent tutorial on pre-load. A properly pre-loaded machine spindle can help cover for some issues. An improperly pre-loaded one merely makes them worse. Plus this is also a very good tutorial on defection and the relationship between pre-load, distance from the first bearing. And the distance from the rear bearing. If two spindles with the same bearings and the same pre-load but with the distance twice as much as the other. The one with a greater distance will have less deflection for the same force. It won't be half as much because other factors such as the rigidity of the shaft etc come into play. Thus is one reason I cringe when I see people running collet chucks on small lathes where the front of the collet is farther from the front bearing than the bearings are from each other.
Also. Any bearing set-up that is pre-loaded to the proper amount is not worth spit if
a) the bearing bores are not on the same centerline
b) the faces of the bottoms of the bores are not perpindicular to the bore centerline
c) the bearing diameters are not concentric
d) the bearing diameters are undersized or out-of-round
e) the shoulders that bearing faces seat against are not perpindicular to the shaft centerline and bearing diameter
f) the faces of any spacers are not parallel to each other. Let's say the spacers are parallel within. 001". Each time the shaft rotates the relationship between the spacer faces will have a wobble effect on the rotating shaft.
Thank you for your interesting comment, Sir. I'm very glad that you as an experienced practitioner find no major fault with the explanations in my video. Greetings, Alex.
@@anengineersfindings
Thank you. Actually you went into more theory than most "instructors" I have ever had the fortune or mis-fortune to have exposure to. The industry I worked in was Automotive Power Train mostly with another 12 years involving large centrifuges for Waste Treatment* plants. The biggest of those were around 800mm in internal diameter. Humboldt, Westphalia and your own products. Average size was 530 to 660. On the automotive side a group of us were sent to a spindle builder for a class (they were supplying the spindles for new machining lines) and I made a comment about how it appeared the spacers on spindles with two bearings mounted back to back had the spacers twice the length of two bearings. The instructor told me i was the first person in one of the heir classes to notice that. This allowed the manufacturer to increase the rigidity and load capacity of the spindle assembly simply by replacing the spacers with two more bearings. The facility closed around 15 years ago and has long since been torn down. I'm sure that who ever bought our Bridgeports at the auction will be in for a surprise when they eventually have to replace the spindle bearings. BP used 2 15° angular contact mou Ted back to back. When I would rebuild our BP heads I changed the bearings over to a 3 bearing set-up with the bottom 2 in tandem. Tool life and finish went up dramatically due to the increased rigidity.
*the company's founder said "it smells like money"
www.google.com/url?sa=t&source=web&rct=j&url=www.centrisys-cnp.com/&ved=2ahUKEwjv1r2NyerwAhWPZM0KHShwA9gQFjANegQICxAC&usg=AOvVaw3iuAKgrKhn7Y7pLUzphjrC
Very well done, and something I will actually use. Your ability to translate engineering principles to practical application is exactly what makes youtube a valuable resource to those of us who want to build well.
Very nicely done!
ATB, Robin
Mr. Renzetti, I hope you've already been told that you are the Vito Corleone of toolmakers. Thank you for your encouraging comment!
high praise from Yoda himself...
@@anengineersfindings I once commented on one of his videos that he is the “Capo Di Tutti Capi” of the CZcams machinist universe.
@@bobolander A Honor it is True !
The brilliance of your spindle model and explanation is demonstrated by the fact that a dummy like me understood the concept.
I appreciate the care you take to create technical explanations that focus on the most important and practical insights. As an engineer in a different field, I know this is hard to do well. Also, I find that your humility and sense of humor make the videos fun to watch!
Thank you very much. Glad if you like my videos.
I though this would be a rather dry subject but you made it quite watchable and lifted the veil of mystery from preload setting. Thank you.
Your my second favorite channel after Robin... great explanation
Who?
It is beautiful how theory matches practics in your movies. I love this university level analysis.
This isn't a movie.
Why can it not be a movie?
I think he means videos.
Well done. I do like the "here's a rule of thumb spec" followed up with a proper analysis and demonstration. Excellent.
For me this a good reason to read and understand the bearing manufactures recommendations for preload ....love your work! Thanks
I always want to hear why pre-load is so important. Making it funny is even better. Hollywood is in your future. I (We) love all your projects. Keep-em coming. Ross,NW Indiana..p.s. I saw RR chirping in on the comments. I watch all of them, Stephan also. Thank You
Thank you very much for your kind words, Mr. Lakich!
Such beautiful educational content on youtube, that is down to earth understanable and usable in the real world. Just perfect. Oh and bud spencer & terence hill running in the background makes it even better. Thanks so much for the video.
Thank you very much. :D So you speak German? As far as I know Bud Spencer and Terence Hill movies are mostly popular in their German dubbed version because of Rainer Brandt's hilarious and timeless one liners.
@@anengineersfindings yes those one liners are just incredible ;) I really appreciate your channel. I studied electronics myself, so mechanical engeneering is not in particular my cup of tea, but your content is so well made and understandble. Again thank you very much for the effort you put into your videos.
Vielen dank für deine Erklärung der technischen Details und vor allem der angemessenen höhe der Vorspannung. Ich hab mich immer gewundert wie ich diese herausfinden kann und jetzt hab ichs für den nächsten Spindelbau verstanden👍🏻
Very good demonstration for preload and what it means to perform bearing adjustment.
i'm gonna have to watch this 3-4 more times before I am able to fully digest everything in here. really really well done video and explanations. now. to re-watch.
Glad if you find the content helpful.
Excellent explanations. I really enjoyed the video.
Good language and communication skills - many thanks for sharing your knowledge!
Nice video as always ! Love the theory explanations.. reminded me of my years at engineering school !
:D give me a heads up if you fall asleep during the video...
@@anengineersfindings Au contraire ! Enjoyed every minute of it :D
Very kind of you! Tanks!
@@anengineersfindings
Just an idea. How well would using a QJ series of bearings
Excellent - I did a similar workup of some duplex bearings last year. The problem I came up with was that the coefficient of expansion made my careful calculations less meaningful than I would have liked. As a bearing turns - it gets warm - expands a bit faster than the surrounding metal.. changing the preload.
I didn't come up with any great solutions - I did think of using something that would deform to measure the pressure - but to see it - one has to open up the bearing again.
Using torque or feel is what many old time machinists told me.
What a great video thank you for taking the time
Another masterclass.👍
Very great explanation, Kind of the quick cut and dry of it all. Great rule of thumb. I know Dedal mentioned the races and balls, so for more precision that would be a concern but for this and for most applications what you explained was perfect, thank you for sharing.
Awesome! Thanks a lot for your educational videos!
You're very welcome. Glad if you like the content.
Very good explanation!
Great explanation
Very interesting, thanks.
Nice video and good explaination, thanks
Hallo Alex, mal wieder ein klasse Video! Hättest du mal Lust deinen "rotary welding positioner" näher zu zeigen?
Auf anhieb fallen mir so viele Details auf das ich wirklich großes Interesse an einem Video darüber hätte!😊
Fascinating.
many thanks!
Thanks for the lecture
Subscribed today, very interesting channel. Atb.
Calculating the axial elongation of the spindle between the bearing shoulder and the nut under 981 N of force would seem to be much simpler. Simply measure the unloaded spindle length, tighten the nut, remeasure and adjust until the elongation is reached. No need to measure bearing stiffnesses and such. One simple calculation and measurement. The hard calculation is determining the proper preload.
Interesting point, as always I guess there are more ways to skin a cat.
The math on your suggestion is as follows: Spindle cross sectional area (50mm^2-36mm^2)/4*Pi=946mm^2; Preload 50kg*9,81m/s^2=491N; Axial stress in spindle due to preload 491N/946mm^2=0,52MPa (!); Axial strain in the spindle due to preload: 0,52MPa/200000MPa=2,6*10^-6=0,00026%;
Axial elongation of the spindle due to preload 2,6*10^-6*40mm=0,1microns (note: this neglects the elongation of the recess at the threads). How to measure this in a non climatized shop in a reliable way?
So in case of the spindle in the video, I doubt that measuring the spindle elongation is easier for setting the preload. Even strain gauges on the spindle would probably deliver no consistent result with these small strains. I guess though your suggestion would work with way higher preloads and a much skinnier spindle.
@@anengineersfindings Fair point. Not knowing the dimensions, I figured the stretch would be a magnitude easier to measure, not sub micron. For such a low clamping force I would probably have considered torquing the nut. A simple equation which I think would be plenty accurate enough for this is 0.2*T*d (kN & mm) to give Nm => 0.2*0.491x50= 5 Nm torque to get close to the 50kg preload (why Europeans use kg for force escapes me). That still seems very low for a 50mm bearing. I would figure the minimum preload recommended by the bearing manufacturer would be a lot more than that. I am however a structural engineer, not a mechanical and besides investigating the SKF bearing manual have no training in bearing design.
Measuring torque on a thread is a notoriously unreliable way to measure axial loading. It's good enough for a nut/bolt arrangement where the primary concern is to not take it past yield, but that's about the limit of its usefulness. The general consensus is that using torque to set axial strain is accurate to within about 25%.
Of course this is just a welding rotator but in the spirit of the exercise that wouldn't be acceptable for bearing assembly on a larger/more critical bearing.
@@hayden6930 I was about to ask a stupid question ... "Can't it be set with a Torque wrench? " But I saw your comment and realized the error of may ways! Pay no attention I am an amateur machinist !
How about applying a thrust bearing, or redesigning the rotator that bearings are indirectly under stress or contact with the load.
I like it.
If I tried your bearing load experiment, I'd end up with 56KG of cast iron weights bouncing all over my nice surface plate!
That's a pretty good lazy susan.
I had to subscribe👊👍
You're Awesome!
:D but I'm sure I can't live up to that....
Great video!!! at what point would you use matched AC bearings? I'd love to see you make a high speed spindle for a small tool like a pcb engraver. I have a NSK 50k spindle which is a dream to use but I've always wanted to try to make a spindle that can do 20k RPM +.
Thanks for your kind comment Jesse, I'll think about it.
Very interesting Video. Which grease are you using? Can't find it. Thanks
The assembly grease I've been using for years is "Liebherr Compund CTK". I assume you might be able to source it from a Liebherr dealer. I'm not affiliated with them in any way, just trying to show some useful stuff.
Will you publish dwgs for this? I love the size. Most others are way to big for my needs. This looks ideal. Really interesting educational video.
If I find the time, I'll think about making drawings for this rotary table. Thanks.
If you don't do drawings you could just do a video describing the device in detail. I would like to know how where you hook up the ground so that the power doesn't go through the bearings. It seems to be quite a clever design.
@@sblack48 You can see his ground connection point in the still image at the very end of the video.
@@hanksshop5964 oh now I see it. Clever! Way better than a strap, better control of contact force. Thanks.
so you say preload should be half of maximum expected force. that is to unload the rear bearing, right? but why would you want to do that? in the example with the springs as long as the weight is smaller than the preload nothing will move. and thats what i would be interested in. threfore preload should be equal to max. force. what am i missing?
I especially like the chuck. What is the brand?
Thanks. I got this chuck used and in a very filthy condition without any brand marking, sorry. In fact, I'd like to know myself who the manufacturere is.
So if the bearing is loose i have to preload orelse if i was milling it would chatter am i right
It's hard to generalize this, but you could say so I guess.
Hallo,
Ich finde ihre Videos sehr interessant. Besonders bewundere ich ihre Kantbank.
Zuzeit studiere ich Allgmeinen Maschinenbau an einer Fachhochschule und bewundere ihr können // Ehrgeiz.
Ist es möglich technische unterlagen//Zeichnungen oder maße von der Kantbank zu bekommen//erwerben ?
Liebe Grüße
Michael
Grüß' Sie Herr Paes, vielen Dank für Ihre netten Worte. Leider ist es mir im Moment nicht möglich, Zeichnungen zu meiner Abkantpresse weiter zu geben, da es von einer externen Seite Bestrebung gibt, meine Konstruktion in Serienproduktion zu bringen. Tut mir leid, aber trotzdem beste Grüße und vielen Dank für Ihr Interesse!
Why not just use a hermann schimidt spin indexer as welding positioner😂
Gut, dass ich nicht Maschinenbau studiert habe. Dann haette ich nicht soviel Vergnuegen dara, hier was zu lernen :-)
:D
ok i amat 7:04 , i pryaed to Jesus and said Lord give me wisdom if you will let me know why the weight drops less with a loaded spring , and this is what hapended >>> " the spring gets stronger the more you compress it " so pressings an unloaded spring offers little resistance , but loading a spring increases its resistance force . the more you press on a spring the more force is needed to continue compressing it." This is hookes law . Hope im right , i get my info from an infinite source of wisdom