New angular bearings on my X2 made the spidle stiffer.. How to overcome it?


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Thread: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

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    Default New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    Hi!

    I had just replaced both the stock bearings of my SIEG X2 Mill (MT3) to angular contact ones (rubber shielded), FAG 7206-B-2RS, using some guides, like Little Machine shop guide: https://littlemachineshop.com/images...ndle%20Kit.pdf and some guides with pictures like this one: https://www.arceurotrade.co.uk/revie...58_X2_Mill.pdf.

    It all went well, I also trammed the spindle head to the back part of the head for left/right and tilt adustments.

    I think the spindle, although having no play at all, and no runout apparently, seems a little bit stiffer than before.

    I don't even need to adjust the left hand nut on the top of the spidle, as the method for inserting the two bearings already left it with no play at all.

    I have a belt drive conversion kit installed also, and removed all the gears inside, even the spindle one.

    I had the belt drive conversion kit modded (added two more pulleys in motor and spindle's original kit's pulleys) to allow also 10.000 RPM, just for engraving. It will be hardly used.

    I think the spindle wiith new bearings, although perfectly aligned, seems stiffer, although not much more than before, and the spindle case gets hotter than before, the higher the speed it runs. At 4600 RPM in 10 minutes it gets to 60 degrees celsius, both the spindle housing, and even the pulleys attached to the spindle.

    I connected a multimeter directly to measure the motor output draw (its rated for 220V - 2.2A)

    With the 600 RPM pulley the motor draws IN IDLE (not endmills attached) at max speed, close to 0.6A

    With the 4600 RPM pulley it draws in idle also almost at max speed too, close to 1.3A

    But with the 10000 RPM pulley it draws almost 2.8A, at 7000RPM, in dle. If I go higher than this the controller stops the motor, for protection. With this high speed pulley the speed has to be reaaaaaaly slowly increased to the point of being useless practically.

    Also it's only being tested in idle, not endmills attached. If I try to turn on the spindle and increase the speed a little bit faster, the current draw increases and the controller stops the motor.

    So I have some doubts:

    Are this Angular Contact bearings really stiffer than the Chinese stock ones, to the point of making the motor work harder than before (draw more current and heat more), when it had the original bearings?

    Will the new bearings (bearings/spindle assembly I mean) , with use, become less stiffer than now, as they're new? Is there a procedure to make it happen, to make it... soften... like run at some speed for some minutes, let it cool down, do it again?

    When I installed the bearings following the instructions on the LMS kit, could I have put too much preload when seating the bearings/spindle? If so, is there a way to undo it a little bit, without damaging the bearings? I'm not even using the top nut over the spindle top.

    Will it be possible/practical to use the higher speed pulleys - 10000RPM - just for engraving, or these bearings aren't meant, or can't handle this speed?

    Thanks for reading!

    Regards, Rodrigo

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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    I do not have a definitive answer for you but can share my experience.
    I installed Japanese angular contact bearings. They did not have shields. I can run the spindle for 3 hours and everything stays almost at room temperature. I do not think the shields on the bearings would make the temperature rise so much.

    Without the motor or pulley attached, my spindle rotates easily. If I spin it by hand as fast as I can, it continues only for 1 or 2 revolutions.

    The temperature rise you describe seems too much to me.

    So my opinion is that you have a problem that needs to be fixed.

    I would suggest three things. 1: disassemble the spindle and verify that the angular contact bearings are installed properly. Usually there is an indication, an arrow, to tell you which way to install it. 2: make sure both bearing are smooth when you turn them in your hand. If they run rough in your hands they are no good. But if they run smooth in your hand it is still possible they will run rough in the machine. 3: when you re-install everything make sure that you do not compress the bearings too much, the left hand nut is only loosly installed. so even before you install the left hand nut, make sure the bearings are not overly compressed.



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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    If you are generating heat with no cutting load then you have too much preload on the bearings or the side loading of the belt drive is inducing too much load. Are you running timing pulleys or V pulleys? A timing pulley doesn't need as much tension on the belt as a V pulley.



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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    Quote Originally Posted by cncuser1 View Post
    I do not have a definitive answer for you but can share my experience.
    I installed Japanese angular contact bearings. They did not have shields. I can run the spindle for 3 hours and everything stays almost at room temperature. I do not think the shields on the bearings would make the temperature rise so much.

    Without the motor or pulley attached, my spindle rotates easily. If I spin it by hand as fast as I can, it continues only for 1 or 2 revolutions.

    The temperature rise you describe seems too much to me.

    So my opinion is that you have a problem that needs to be fixed.

    I would suggest three things. 1: disassemble the spindle and verify that the angular contact bearings are installed properly. Usually there is an indication, an arrow, to tell you which way to install it. 2: make sure both bearing are smooth when you turn them in your hand. If they run rough in your hands they are no good. But if they run smooth in your hand it is still possible they will run rough in the machine. 3: when you re-install everything make sure that you do not compress the bearings too much, the left hand nut is only loosly installed. so even before you install the left hand nut, make sure the bearings are not overly compressed.
    In my setup, without the V pulley attached, if I rotate by hand my spindle gives 1/3 of a spin only.

    Before installing the AC bearings, both bearings seemed smooth but didn't spin easily. Also, as they are Angular contact, the center of them wobbles before the spindle is inserted into them, So I coudn't test for a spin before installing them. The bearings made no noise, and after installation, they still run silent, no strange noises, no roughness on them, at least to my ears. The spindle runs silent.

    When I installed them, i noticed that they didn't slip easily through the spindle. They had a really tight fit on the spindle

    Is it possible to remove the AC bearings without destroying them? I read somewhere it's not possible. I used those instructions of Little Machine Shop for removal of the stock ones and installation of the new ones. Can I use the same procedure to remove them?

    Thanks for the help!



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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    Quote Originally Posted by Kenny Duval View Post
    If you are generating heat with no cutting load then you have too much preload on the bearings or the side loading of the belt drive is inducing too much load. Are you running timing pulleys or V pulleys? A timing pulley doesn't need as much tension on the belt as a V pulley.
    Hi Kenny!

    I'm using V pulleys, with not to much tension. They're quite thin actually.

    Using the instructions of Little Machine shop for assembly/disassembly of the bearings, I don't know how to put or not preload during installation.
    The reason is that the lower bearing is first installed inside the spindle until it is seated the lower step of the spindle. Then the spindle/lower bearing assembly is pulled upwards with a system (pipe) that pushes the upper bearing down untill it's fully seated, as the lower one is being pushed upwards. So both bearings are pushed to their seats at the same time. So by using this method I can't individually install the bearings. Is there another way of installing the bearings/spindle?

    I know the fit of the spindle inside the bearings is really tight. It's impossible to put the spindle inside the bearings by hand.

    Thanks for your help!



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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    Heat only comes from friction and that is created by either squeezing the AC bearing together too much, misalignment of something in the stack or lots of side load introduced either by cutting forces or some other mechanism such as the belt tension on the belt drive. If the belt isn't a banjo string then I'd be looking at taking the spindle apart again and rechecking everything. There is no way turning the spindle alone should ever get the machine to shutdown if everything is fit together well.

    Last edited by Kenny Duval; 12-18-2019 at 07:28 PM.


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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    The comment about belt tention is a good one, it should be investigated


    Quote Originally Posted by Rimbaldo View Post
    Also, as they are Angular contact
    ....what is the part number for the bearings, do you have a link to the technical specifications.

    Your comment about wobbles....my bearings didn't wobble



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    Quote Originally Posted by cncuser1 View Post
    The comment about belt tention is a good one, it should be investigated


    ....what is the part number for the bearings, do you have a link to the technical specifications.

    Your comment about wobbles....my bearings didn't wobble

    Sorry, English is not my first language. By “wobble” I meant that before installing the bearings in the spindle, the inner race had some small...movement... play...to any direction and if I remember, up and down also, in relation to the outer race. Different from the stock bearings, in which the inner race rotates perfectly centered around the outer ring. And doesn’t move to anywhere besides rotating.

    After installation there’s no play, no weird sounds, no “wobble”

    The bearings are FAG 7206B-2RS-TVP. You can check them in this link:

    https://www.bearing-king.co.uk/bearing/7206-b-2rs-tvp-fag-x-life-sealed-angular-contact-bearing-30x62x16mm/24338

    I installed them both with the thicker part of the inner races facing the outside of the spindle head case.

    My runout is less than 0.01mm. Is this good at least?

    Also, I notice heat only when running at 4000rpm or more. If I use the low speed pulley, that reaches 1600 RPMs, the head and motor and spindle remains at 30 degress celsius.



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    Quote Originally Posted by Rimbaldo View Post
    Sorry, English is not my first language. By “wobble” I meant that before installing the bearings in the spindle, the inner race had some small...movement... play...to any direction and if I remember, up and down also, in relation to the outer race. Different from the stock bearings, in which the inner race rotates perfectly centered around the outer ring. And doesn’t move to anywhere besides rotating.

    After installation there’s no play, no weird sounds, no “wobble”

    The bearings are FAG 7206B-2RS-TVP. You can check them in this link:

    https://www.bearing-king.co.uk/bearing/7206-b-2rs-tvp-fag-x-life-sealed-angular-contact-bearing-30x62x16mm/24338

    I installed them both with the thicker part of the inner races facing the outside of the spindle head case.

    My runout is less than 0.01mm. Is this good at least?

    Also, I notice heat only when running at 4000rpm or more. If I use the low speed pulley, that reaches 1600 RPMs, the head and motor and spindle remains at 30 degress celsius.
    I run my spindle at about 4K rpm max , so our temperatures are similar.

    I think I understand what your description of the "wobble". I am not an expert but I do not remember my bearing having this.

    Also I am pretty sure I only installed one AC bearing in the spindle, near the cutter. The bearing near the pulley was a normal bearing. I will look later. You must be very sure the bearing was installed with the contact angle facing the correct direction.

    I will look later about how the bearings should be installed.



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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    Quote Originally Posted by cncuser1 View Post
    I do not have a definitive answer for you but can share my experience.
    I installed Japanese angular contact bearings. They did not have shields. I can run the spindle for 3 hours and everything stays almost at room temperature. I do not think the shields on the bearings would make the temperature rise so much.
    Do you have the part number for the bearings you installed?



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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    Shanghyd: I orded one of each
    https://www.bearingscanada.com/Produ...7007CP5-ABEC-5
    https://www.bearingscanada.com/Produ...tCode=7206C-P5

    I made a mistake in my previous post, both are angular contact.



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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    When ever you change bearings, you have to run them for a while (5 min) at low RPM without load. Than gradually increase the RPM a bit and again let it run a while. Repeat this procedure until you run at max rpm. The whole process will take about half an hour. Doing so will gradually warmup the bearing, and this will spread the lubrication in the bearing.

    Contact angle bearings will generate more heat then ball bearings under the same conditions and tapered bearings will generate even more heat.

    You must not exceed the maximum speed the bearings are specified.

    If after running in, under no load, not exceeding the bearings max RPM, the bearings get hot (can't hold them for a while meas ++50°), the preload is to much.

    Your original bearings where ball bearings and they where pressed fit. Your contact angle bearing, at the side of the preload nut, needs to move "freely"on the axis to set the preload. Because the axis was made for press fit (it is to thick), the contact angle bearing can't move freely. It is (strongly) pressed on the axis and probably with to much preload. This is a common problem when replacing ball bearings by contact angle bearings and very difficult to avoid.
    There is not a good fix for this but in time (a few hours of use under load) the problem will get less due to the "running in" of the bearing.

    Machine setups using contact angel bearings are stiffer than ball bearings due to the preload. The preload also eliminates the play as long as the load on the bearing is less than the preload. Using more preload than the actual maximum load will not improve the machined part, just increase the wear.

    Even knowing all this, I also had to much preload when I replaced the ball bearings by contact angle bearing on my mini lathe. For what it is worth, I can't say the turning results are improved. Maybe this is because the turning results where already OK or the old ball bearings where still good.



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    Quote Originally Posted by hfjbuis View Post
    When ever you change bearings, you have to run them for a while (5 min) at low RPM without load. Than gradually increase the RPM a bit and again let it run a while. Repeat this procedure until you run at max rpm. The whole process will take about half an hour. Doing so will gradually warmup the bearing, and this will spread the lubrication in the bearing.

    Contact angle bearings will generate more heat then ball bearings under the same conditions and tapered bearings will generate even more heat.

    You must not exceed the maximum speed the bearings are specified.

    If after running in, under no load, not exceeding the bearings max RPM, the bearings get hot (can't hold them for a while meas ++50°), the preload is to much.

    Your original bearings where ball bearings and they where pressed fit. Your contact angle bearing, at the side of the preload nut, needs to move "freely"on the axis to set the preload. Because the axis was made for press fit (it is to thick), the contact angle bearing can't move freely. It is (strongly) pressed on the axis and probably with to much preload. This is a common problem when replacing ball bearings by contact angle bearings and very difficult to avoid.
    There is not a good fix for this but in time (a few hours of use under load) the problem will get less due to the "running in" of the bearing.

    Machine setups using contact angel bearings are stiffer than ball bearings due to the preload. The preload also eliminates the play as long as the load on the bearing is less than the preload. Using more preload than the actual maximum load will not improve the machined part, just increase the wear.

    Even knowing all this, I also had to much preload when I replaced the ball bearings by contact angle bearing on my mini lathe. For what it is worth, I can't say the turning results are improved. Maybe this is because the turning results where already OK or the old ball bearings where still good.

    Thanks a lot! Really good explanation. I guess I’ll use the mill for some time to check if the spindle/bearings get better with time.. won’t try to remove and re-install the bearings right now!



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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    Removing and reinstalling probably won't fix the problem and there is a high risk you damage the bearing.

    I guess the the replacement bearings the mill manufacturer sells, are designed as replacement and have a slightly larger bore diameter.

    Look at this chart for more information https://www.skf.com/binary/21-292339..._12-292339.png



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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    Quote Originally Posted by Rimbaldo View Post
    Sorry, English is not my first language. By “wobble” I meant that before installing the bearings in the spindle, the inner race had some small...movement... play...to any direction and if I remember, up and down also, in relation to the outer race. Different from the stock bearings, in which the inner race rotates perfectly centered around the outer ring. And doesn’t move to anywhere besides rotating.

    After installation there’s no play, no weird sounds, no “wobble”

    The bearings are FAG 7206B-2RS-TVP. You can check them in this link:

    https://www.bearing-king.co.uk/beari...x62x16mm/24338

    I installed them both with the thicker part of the inner races facing the outside of the spindle head case.

    My runout is less than 0.01mm. Is this good at least?

    Also, I notice heat only when running at 4000rpm or more. If I use the low speed pulley, that reaches 1600 RPMs, the head and motor and spindle remains at 30 degress celsius.
    You have Ac Bearing by that part number 40 degree which is higher than normal for these spindle bearing, but won't cause any problem just can take a higher loading, the press fit may be to tight for the grade of bearing you are using this will cause over heating for removing yes you could damage them if they are too tight on the spindle shaft

    So the fit on the shaft is very important

    You can also remove the inner seals this can reduce the friction but you also can loose the grease in the top Bearing also by doing this

    The normal mounting for spindle Bearings like this is called Back to Back so you may have them mounted Face to Face which still will work but not as good as Back to Back this snip may help

    Attached Thumbnails Attached Thumbnails New angular bearings on my X2 made the spidle stiffer.. How to overcome it?-ac-bearing-mounting-png  
    Mactec54


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    Quote Originally Posted by mactec54 View Post
    You have Ac Bearing by that part number 40 degree which is higher than normal for these spindle bearing, but won't cause any problem just can take a higher loading, the press fit may be to tight for the grade of bearing you are using this will cause over heating for removing yes you could damage them if they are too tight on the spindle shaft

    So the fit on the shaft is very important

    You can also remove the inner seals this can reduce the friction but you also can loose the grease in the top Bearing also by doing this

    The normal mounting for spindle Bearings like this is called Back to Back so you may have them mounted Face to Face which still will work but not as good as Back to Back this snip may help

    So I’ll have to live with that this way. At lower RPMs, it runs silent and cool. Will this stiffness decrease over time with use?

    I mounted the bearings this way in the picture attached: inner part to the outside, upper and lower. Is it back to back?

    Thanks!

    Attached Thumbnails Attached Thumbnails New angular bearings on my X2 made the spidle stiffer.. How to overcome it?-30d2aed8-f1d8-4c72-bcb6-3169205e8fd4-jpeg  


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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    Quote Originally Posted by Rimbaldo View Post
    So I’ll have to live with that this way. At lower RPMs, it runs silent and cool. Will this stiffness decrease over time with use?

    I mounted the bearings this way in the picture attached: inner part to the outside, upper and lower. Is it back to back?

    Thanks!
    If the thinnest section of the outer Bearing race is facing out then you have them Back to Back as per the snip

    Mactec54


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    Default Re: New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

    Will this stiffness decrease over time with use?
    Yes, in time you will get some play and this will decrease "stiffness". But it will take a long time and if it happens, you can reduce/eliminate this play by retentioning the lock nut. At some stage, the hardened layer of the bearing will wear out and you have to adjust the preload more often. Than it is time to replace the bearings. Also the runout will suffer from worn bearings.

    You measured less than 0.01 mm runout, that isn't bad at all. You have to measure the spindle runout at the spindle shaft itself on the inner side of the taper. You should also measure the play of the spindle. Make a note of these measurements and repeat the the measurement periodically. This way you will see the wear and tear of the spindle bearings.
    Also measure the runout at the shaft of an end mill and compare it with the runout of the spindle. The runout of the end mill normally is caused by the collet. Normally the runout at the spindle is far less than the runout at the end mill. If it matters, depends on the accuracy you want. If you have a router, the inaccuracy of the router is far larger then the runout at the spindle.

    Runout will cause to much material to be cut away. If you measure the results of the finished product, you can adjust the CNC program to compensate for this on the next (same) part you make.



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    Quote Originally Posted by hfjbuis View Post
    Yes, in time you will get some play and this will decrease "stiffness". But it will take a long time and if it happens, you can reduce/eliminate this play by retentioning the lock nut. At some stage, the hardened layer of the bearing will wear out and you have to adjust the preload more often. Than it is time to replace the bearings. Also the runout will suffer from worn bearings.

    You measured less than 0.01 mm runout, that isn't bad at all. You have to measure the spindle runout at the spindle shaft itself on the inner side of the taper. You should also measure the play of the spindle. Make a note of these measurements and repeat the the measurement periodically. This way you will see the wear and tear of the spindle bearings.
    Also measure the runout at the shaft of an end mill and compare it with the runout of the spindle. The runout of the end mill normally is caused by the collet. Normally the runout at the spindle is far less than the runout at the end mill. If it matters, depends on the accuracy you want. If you have a router, the inaccuracy of the router is far larger then the runout at the spindle.

    Runout will cause to much material to be cut away. If you measure the results of the finished product, you can adjust the CNC program to compensate for this on the next (same) part you make.

    Thanks a lot for all your detailed explanations. I got it all now. I’ll leave it this way then. Won’t mess with the spindle anymore. Don’t know if changing the stock bearings to these was a good move, but my mill is working fine and silent. Don’t know if in heavy cuts this stiffness will stall the motor or not, but so far so good! I’m using the low speed pulleys (1600 max RPM) and it’s working really nice...



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New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

New angular bearings on my X2 made the spidle stiffer.. How to overcome it?

New angular bearings on my X2 made the spidle stiffer.. How to overcome it?