Mill Spindle Runout problem - considering grinding - Page 2
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  1. #21
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    Quote Originally Posted by Richard King View Post
    I agree, advising to grind the spindle on an old machine without checking the spindle and bearings is not what any professional rebuilder would do would do. Has Barry from H&W been asked? He is our resident knee mill expert. If it's bent and you grind it and then decide to replace the bearings in 1 year, you will have to regrind it. Does that sound right????
    It's not the perfect solution,but what does he have to lose? You guys know a hell of lot more than I do about this subject, but I cannot see the downside of cleaning it up in situ, outside of some catastrophic grinding error that trashes the whole spindle.

    My point was that if it is bent, and you don't grind it and the bearings are good,it will have to be reground anyway.

    Are we in agreement, that no matter what, that spindle needs a regrind?

    Just a guess, but from the condition of that taper, that machine has been running a long time on those bearings.

    Like all material things, it is just a money issue. Spend a day and a few bucks and do a careful setup and grind, or start adding money toward perfection. No doubt Wells could do a complete rebuild, or a professional rebuilder could come out and regrind it on site, or it could be sent out- all things that might be worth it to a production guy. Without knowing what the OP expects from the machine, it is hard to qualify.
    It was easy for me on the VN- the machine was worth maybe a grand, and there was no way to justify a professional rebuild-regrind. Plus Forrest gave it the OK

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    For the evidence presented in this thread and my limited experience, I don't see any reason why this spindle would be need to be reground now as it sits.
    If, like I suspect, it's bent, a regrind right now would only waste good material and would bring the spindle out of spec when the bending is removed.
    It could be a situation similar to Chris' Hurco, with the distortion introduced by reassembling the spindle with a bur or a chip trapped somewhere. If that's the case, fixing that problem would bring back the spindle into specs, without any regrind before and after.

    Paolo

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  4. #23
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    Quote Originally Posted by stoneaxe View Post
    It's not the perfect solution,but what does he have to lose? You guys know a hell of lot more than I do about this subject, but I cannot see the downside of cleaning it up in situ, outside of some catastrophic grinding error that trashes the whole spindle.

    My point was that if it is bent, and you don't grind it and the bearings are good,it will have to be reground anyway.

    Are we in agreement, that no matter what, that spindle needs a regrind?

    Just a guess, but from the condition of that taper, that machine has been running a long time on those bearings.

    Like all material things, it is just a money issue. Spend a day and a few bucks and do a careful setup and grind, or start adding money toward perfection. No doubt Wells could do a complete rebuild, or a professional rebuilder could come out and regrind it on site, or it could be sent out- all things that might be worth it to a production guy. Without knowing what the OP expects from the machine, it is hard to qualify.
    It was easy for me on the VN- the machine was worth maybe a grand, and there was no way to justify a professional rebuild-regrind. Plus Forrest gave it the OK
    Well, that may be, but if the spindle is bent and the taper is ground that way he'll be grinding it twice, which is also a waste of time since he'll have to repeat the grinding again later. Grinding it in place without getting rid of the bend/runout means it will be out of balance too - at 3,000 - 4,000 RPM that can cause pretty significant vibration.

    Having that kind of runout both inside and out means that the spindle O.D. is concentric with the I.D. but is running out due to either a bent spindle, terribly sub-par assembly work or some very bad bearings. I don't think that much runout is possible without at least one of those things. Regrinding a spindle in place because the taper is worn but true is a completely different scenario.

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    Quote Originally Posted by eKretz View Post
    Well, that may be, but if the spindle is bent and the taper is ground that way he'll be grinding it twice, which is also a waste of time since he'll have to repeat the grinding again later. Grinding it in place without getting rid of the bend/runout means it will be out of balance too - at 3,000 - 4,000 RPM that can cause pretty significant vibration.

    Having that kind of runout both inside and out means that the spindle O.D. is concentric with the I.D. but is running out due to either a bent spindle, terribly sub-par assembly work or some very bad bearings. I don't think that much runout is possible without at least one of those things. Regrinding a spindle in place because the taper is worn but true is a completely different scenario.
    He'll also thin or even go trough the hard layer. Should there be one , of course. The type of runout he seems to have is not good news.
    Last edited by Orbital77; 04-18-2021 at 10:57 AM.

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    The OP is a You Tuber and he has increased his income with us watching his show. Another example of poor advise given on You Tube. There is valuable advice on You Tube but it seems many of us agree grinding a spindle without checking to see if it is bent first, is BAD Advice. Let close this and go to the next question.

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    Quote Originally Posted by Richard King View Post
    The OP is a You Tuber and he has increased his income with us watching his show. Another example of poor advise given on You Tube. There is valuable advice on You Tube but it seems many of us agree grinding a spindle without checking to see if it is bent first, is BAD Advice. Let close this and go to the next question.
    Thank you for your valuable suggestion.

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    Barry said he believe that grinding the spindle would correct the issue. He also says that a spindle should not be ground in relation to the bearings, but ground on its own.

    +1 to everyone (it would take too long to name everyone) recommending disassembly and properly checking to see where the issue is.

    Jon

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    All, first my apologies for the delay in getting back to the thread. I sincerely appreciate all of the time you've spent commenting. I've been very busy at work and also ran into some problems dropping the quill out of my mill which unfortunately involved me 'putting on my big boy pants' and removing half of the upper head and the motor and unfortunately I dont have any hoisting in my garage. This was due to the end of the spline of the spindle being ever so slightly dinged (not even enough to see by eye). So I had to remove the motor to get to the variable speed pully to expose the top of the spline so I could gently file with a needle file. 2 days to take it apart, 5 mins of filing then quill dropped smoothly.

    So, quill was out and then I removed the upper retaining ring on the top spindle bearing and then gently tapped the spindle out of the quill with the 2 expensive bearings intact on the lower portion of the spindle. You can see from the pictures in the video they are captive by a whittet-higgins BearHug BH-08 locking nut which I was NOT able to remove yet despite a pretty good effort and a few words of frustration.

    The deeper i've gotten into all the measurements and trying to keep track of all i've done, I decided to record as much as possible and i've compiled it into a video.
    https://youtu.be/VidW2-4QSuE. And BTW, my channel is not monetized...

    Im sure I haven't indicated everything perfectly but hopefully this will give a good picture of what I'm dealing with. What you'll see in the video is some wear on the inner bore of the quill where the precision bearings sit. Unfortunately I didn't measure how deep it is but will try to soon. As you'll see toward the end of the video, i'm able to deflect/wiggle the spindle about 5 tenths without it springing back so i'm starting to think this may be a definite contributor to the problem. Regarding the bearings, i'm trying to track down some new/old stock of the bearings on Ebay. I'm not having a lot of luck at the moment based on the bearing info I got from Wells. FAG 108HDL G4. It will be a pair of them. I did speak with Wells-Index about the latest findings and they said they could potentially smooth up the inner bore where the bearings seat, Chrome it and then grind it back down to spec. Unsure of the price on that yet.

    So I have it back together at the moment while I try and figure out next steps and it doesn't seem any worse than it was and doesn't sound any different either. Again, I want to thank you all for the comments and sorry again for the delay in getting back. Hopefully the video will shed some light.

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    Quote Originally Posted by Richard King View Post
    The OP is a You Tuber and he has increased his income with us watching his show. Another example of poor advise given on You Tube. There is valuable advice on You Tube but it seems many of us agree grinding a spindle without checking to see if it is bent first, is BAD Advice. Let close this and go to the next question.
    Hi Richard, i'm the OP and it's unclear if you were suggesting I was fishing for views or if you're talking about the other video I referenced about the spindle grind. My YT channel isn't monetized so not sure why the comment and I definitely am not giving advice, only seeking from you guys that know much more than I on the subject. I posted another reply to the thread and sorry for not getting back sooner.

    cheers

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    I seen damage similar to a mill, where a tool in the spindle was struck by a moving fork lift. It caused damage to the bearing seat in the spindle housing.
    There has been some post about Wells Index over the years repairing spindles, non of it bad.
    On another note, I have been accused of somehow attempting to profit myself from this forum, and I find it outrageous that that type of accusations seem to continue, as it can clearly be seen, not a single dime can be made here, when a dollar can be easily made most anywhere else, Get Real!

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    You need to get the entire thing disassembled, spindle bearings and all. Then put it between centers or in v-blocks that only contact a narrow area - those wide v-blocks are no good for checking TIR. You can use small pieces of shim like 3/8" HSS tools that are flat ground or something like that on top of those wide v-blocks to get the same effect. You need to know TIR of all the bearing diameters and the faces too - can't do that with bearings mounted. Don't just check and go by memory - write it down. And clock the different measurements to each other so you know their angular relationship.

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    You should inspect not only the spindle But the housing where the bearings seat too
    Roundness ecspecially On old machines I never found a housing that was to specs Well At least the few times I had the equipment to measure it accurate enough To measure if the bores are within allignment is not that easy Many people inspect the spindle and assume the housing is still correct

    Peter

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    Quote Originally Posted by eKretz View Post
    You need to get the entire thing disassembled, spindle bearings and all.
    Yes, good point and this is/was my plan. I attempted to get that spindle nut off and it proved to be a serious challenge. I buggered up a couple of the slots and stopped before it got any worse. I'll either try again with a proper spline wrench and maybe 2 opposing spanner wrenches or if I ultimately decide to send to Wells will let them remove and assess.
    Quote Originally Posted by eKretz View Post
    Then put it between centers or in v-blocks that only contact a narrow area - those wide v-blocks are no good for checking TIR. You can use small pieces of shim like 3/8" HSS tools that are flat ground or something like that on top of those wide v-blocks to get the same effect. You need to know TIR of all the bearing diameters and the faces too - can't do that with bearings mounted. Don't just check and go by memory - write it down. And clock the different measurements to each other so you know their angular relationship.
    Thank you. This is an excellent explanation. And yes for writing down. I need to be more thorough and notes don't lie.

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    Quote Originally Posted by Peter from Holland View Post
    You should inspect not only the spindle But the housing where the bearings seat too
    Roundness ecspecially On old machines I never found a housing that was to specs Well At least the few times I had the equipment to measure it accurate enough To measure if the bores are within allignment is not that easy Many people inspect the spindle and assume the housing is still correct

    Peter
    Thanks Peter. Good point about checking the alignment of the bores where the bearings seat. I definitely don't have the tools to measure this accurately which again feels like it may be best for me to send to Wells...

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    I'm surprised you didn't check the runout of the taper in the bore of the spindle while you had it laying the vee blocks. Been real easy to do. Also could have indicated the OD of the spindle nose while in the vee blocks, too.

    Your bearings look bad! Looks like it has been over heated many times from the lack of lubricant. Just saying. The bearing numbers you mentioned can be matched up to many different brands of bearings out there, not just the one specified. The 108HDL number is equivalent to 7008DULxxxx number and possibly others out there. Ken

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    So I pulled the quill/spindle again last night and got the bearing spanner nut off. I was then able to press the spindle bearing pair off and have been able to identify the ones on my machine. Looks like they've been replaced as they aren't the ones Wells-Index mentioned. They are MRC 108KRDS ABEC3. The spindle is now bare as well so I will spend some time measuring and recording my findings.

    img_1148.jpgimg_1150.jpg

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    My older bearing book, 1974 edition, does not show MRC 108KRDS, it shows 7108KR__ as a angular contact spindle bearing. It also shows a standard MRC bearing with the number of 108KS__. The bearing your showing us does not look like a angular contact spindle bearing, just a regular ball bearing. This maybe why you are getting runout issues. But you still need to put the spindle up in your vee blocks and check the runout of the taper on the ID of the spindle for us.

    Your best bet is to box it all up in a wooden box and ship it to Wells-Index and let them rebuild your spindle for you. Ken

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    I am facing a similar issue right now

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    Quote Originally Posted by 4GSR View Post
    My older bearing book, 1974 edition, does not show MRC 108KRDS, it shows 7108KR__ as a angular contact spindle bearing. It also shows a standard MRC bearing with the number of 108KS__. The bearing your showing us does not look like a angular contact spindle bearing, just a regular ball bearing. This maybe why you are getting runout issues. But you still need to put the spindle up in your vee blocks and check the runout of the taper on the ID of the spindle for us.

    Your best bet is to box it all up in a wooden box and ship it to Wells-Index and let them rebuild your spindle for you. Ken
    Interesting comment about these possibly not being angular contact bearings. On visual inspection they appear to have the characteristics of thicker on one side thinner on the other side for each race as shown in this diagram.
    angular-contact-bearing-diagram.jpg

    Also, I agree regarding sending to Wells-Index. However I do have the spindle out and will perform these measurements before sending and will share the findings here.

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    I think Ken was assuming you were showing both sides of the bearing, instead of the same side of both of them, so it looked visually like they weren't A.C. bearings. A quick google search shows that they are indeed A.C. bearings.

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