Mill Spindle Runout problem - considering grinding
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    Default Mill Spindle Runout problem - considering grinding

    Here's a video I put together to explain the problem. The high level written description is as follows:
    Wells-Index spindle runout problem - YouTube


    The TIR on the outside lower body of spindle is reading .002-.003 runout
    The inside of the R8 Taper is also reading the same .002-.003 runout. High points and low points are the same on the inside and out.
    Above the taper inside the spindle, the TIR is consistent at .0002-.0003 (2-3 tenths). This is roughly in spec for the machine.
    The taper isn't making uniform contact around the circumference of the collet.
    I'm considering attempting to setup and grind the taper similar to how Shadon HKW did in his YT video.
    R 8 Spindle regrind - YouTube




    I did not crash the spindle. I've had the machine just over a year and as far as I can tell, it's been this way since I got it. It's almost as if the spindle was manually ground previously and was ground off center by the 2-3 thou i'm seeing now. And potentially the outer body of the spindle was reground at the same time which could be why the runout is the same on the inside of the taper and the outside of the body at the same spots.

    Any thoughts or suggestions welcome.
    Last edited by paulymorph; 04-13-2021 at 07:46 PM.

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    Quote Originally Posted by paulymorph View Post
    Here's a video I put together to explain the problem. The high level written description is as follows:
    Wells-Index spindle runout problem - YouTube


    The TIR on the outside lower body of spindle is reading .002-.003 runout
    The inside of the R8 Taper is also reading the same .002-.003 runout. High points and low points are the same on the inside and out.
    Above the taper inside the spindle, the TIR is consistent at .0002-.0003 (2-3 tenths). This is roughly in spec for the machine.
    The taper isn't making uniform contact around the circumference of the collet.
    I'm considering attempting to setup and grind the taper similar to how Shadon HKW did in his YT video.
    R 8 Spindle regrind - YouTube




    I did not crash the spindle. I've had the machine just over a year and as far as I can tell, it's been this way since I got it. It's almost as if the spindle was manually ground previously and was ground off center by the 2-3 thou i'm seeing now. And potentially the outer body of the spindle was reground at the same time which could be why the runout is the same on the inside of the taper and the outside of the body at the same spots.

    Any thoughts or suggestions welcome.
    I think you are right and it's re-grinding time. The question is if you should take it apart or re-grind in it's own bearings. I've no idea which one is better as I know not the condition of the bearings, how well are they installed and how much ( if any ) gear noise you might expect.

    I have the feeling the poster CarbideBob knows waaaaaaaay more than I do about these things and I suggest you contact him via a PM.

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    Quote Originally Posted by paulymorph View Post
    The TIR on the outside lower body of spindle is reading .002-.003 runout
    The inside of the R8 Taper is also reading the same .002-.003 runout. High points and low points are the same on the inside and out.




    It's almost as if the spindle was manually ground previously and was ground off center by the 2-3 thou i'm seeing now. And potentially the outer body of the spindle was reground at the same time which could be why the runout is the same on the inside of the taper and the outside of the body at the same spots.
    what is a "manual grind"? .. and no, I do't think that's what caused it...whatever that is.

    yes, you desperately need a regrind, that is one trashed taper, I'm not even sure HOW they effed it up like that. bluing and printing that sad mess, especially with a Shars collet was kinda pointless, LOL! what did you think you would learn, that it was perfect?

    the measurement of the un-ground area above the dumpster fire that passes for a taper is completely pointless as well, that was never a precision surface.

    how to proceed all depends on the spindle bearings, what you are going for as a goal, and the time and money available.

    unless its had a refurb and new bearings, I can't imagine they are any good based on the trashing the taper took.
    I'd do some careful evaluation of the unit to decide, like put a 3/4 rod in it and see how much deflection you get with some moderate side force, put it in neutral and spin it to feel how it feels, and check for end play.

    if they are loose, and you get a rough feel, more than 1-2 thou deflection (with the quill locked of course), or more than .0005 end (axial) play, there is really no point doing a re-grind. that has to be addressed first.

    wether YOU ever crashed it matters not a wit, unless you are the only user its seen in its life. if the bearings are tight (meaning they were replaced or tightened up somehow I'd think), and the high and low spots are the same inside and out, it seems likely to me the spindle is bent. that may be hard to do, but the animal that trashed the taper could have managed that too. again, the feel turning by hand will be telling, ( IF its tight).

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    Quote Originally Posted by Orbital77 View Post
    I think you are right and it's re-grinding time. The question is if you should take it apart or re-grind in it's own bearings. I've no idea which one is better as I know not the condition of the bearings, how well are they installed and how much ( if any ) gear noise you might expect.

    I have the feeling the poster CarbideBob knows waaaaaaaay more than I do about these things and I suggest you contact him via a PM.
    Thanks for the comments. I'll message him.

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    Quote Originally Posted by cyanidekid View Post
    what is a "manual grind"? .. and no, I do't think that's what caused it...whatever that is.
    Manual grind was a bad choose of words. Just mean it seems like it might have been reground but poorly done which might account for the runout in the taper.

    Quote Originally Posted by cyanidekid View Post
    yes, you desperately need a regrind, that is one trashed taper, I'm not even sure HOW they effed it up like that. bluing and printing that sad mess, especially with a Shars collet was kinda pointless, LOL! what did you think you would learn, that it was perfect?
    I learned there wasn't uniform pressure being applied around the collet. Potholes aside, the rub points and gap at the bottom was an interesting detail. But maybe it doesn't help diagnose the prob...


    Quote Originally Posted by cyanidekid View Post
    the measurement of the un-ground area above the dumpster fire that passes for a taper is completely pointless as well, that was never a precision surface.
    Understood but I do think it confirmed that the runout is only a byproduct of the taper and not the spindle body itself?

    how to proceed all depends on the spindle bearings, what you are going for as a goal, and the time and money available.

    Quote Originally Posted by cyanidekid View Post
    bearings seem smooth, no sounds coming from them and smooth turning.
    Not opposed to spending some $ but may be tough to come up with the $ for sending out the spindle for regrind-rebuild.

    Unless its had a refurb and new bearings, I can't imagine they are any good based on the trashing the taper took.
    I'd do some careful evaluation of the unit to decide, like put a 3/4 rod in it and see how much deflection you get with some moderate side force, put it in neutral and spin it to feel how it feels, and check for end play.

    if they are loose, and you get a rough feel, more than 1-2 thou deflection (with the quill locked of course), or more than .0005 end (axial) play, there is really no point doing a re-grind. that has to be addressed first.

    Quote Originally Posted by cyanidekid View Post
    Whether YOU ever crashed it matters not a wit, unless you are the only user its seen in its life. if the bearings are tight (meaning they were replaced or tightened up somehow I'd think), and the high and low spots are the same inside and out, it seems likely to me the spindle is bent. that may be hard to do, but the animal that trashed the taper could have managed that too. again, the feel turning by hand will be telling, ( IF its tight).
    Bearings are not tight. No bad sounds and very little deflection when I pulled against a 1/2 endmill at the shank (spindle locked), but i'll check again.

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    Why don't you just call them? They build the machines and do repairs....



    Wells Index
    701 West Clay Ave.
    Muskegon, MI 49440-1064
    TEL: 1-800-456-7409
    TEL: (231) 759-0950
    FAX: (231) 728-7456
    E-MAIL: [email protected]

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    Quote Originally Posted by JS View Post
    Why don't you just call them? They build the machines and do repairs....



    Wells Index
    701 West Clay Ave.
    Muskegon, MI 49440-1064
    TEL: 1-800-456-7409
    TEL: (231) 759-0950
    FAX: (231) 728-7456
    E-MAIL: [email protected]
    Not only do they.. Wells-Index can remove that silly Are Ate and get it back to you with a 30-taper or even 40-taper.

    And not only?

    IIRC, they also do repair and mods on spindles they did NOT even build. OTHER maker's mills.

    Why would they not? Once equipped, tooled, and trained and experienced at what works and what does not, it is much the same tasking and metrology, brand immaterial.

    End of MANY problems.
    Last edited by thermite; 04-14-2021 at 03:31 AM.

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    Quote Originally Posted by cyanidekid View Post
    .

    HUH??? WTF? why are you dragging CarbideBob into this??? that's nuts. he knows more about a lot of things than most of us, but that's not his business, his interest, or a respectful use of his time, leave him out of it.
    "This comment deleted by moderator, please do not use this type of language in the future..."

    CarbideBob is member and very frequent contributor here, may not read each and every post and a PM directing him to this one is nothing out of the very ordinary.
    Last edited by CBlair; 04-14-2021 at 08:19 AM.

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    I concur that the problem seems a bent spindle. the runout at the end might be just the tip of the iceberg and regrinding it would be like putting expensive lipstick on a pig.

    I wouldn't be too concerned about the seemingly poor contact on your taper: the three contact points are evenly spaced at 120° and, anyhow, the contact points of a collet like C5, R8, etc., collapsible only at one end change with the diameter of the piece they clamp (i.e. if the rod is larger than "nominal diameter" the contact points will be in the middle of the circular sectors, close to the tip of the collet; if the rod is "undersized", the contact points will be at the ends of the circular sectors, more toward the inside of the taper).

    A couple of thousands runout relatively close to the bearings, to me it seems really a lot, especially if is due to a bent spindle: you put in new bearings and you either destroy them immediately, or you trash the housing, since the inner race would be tilted in comparison to the outer race.

    My suggestion would be to disassemble the spindle and assess it. Perhaps, you'll need to replace it, unless you manage to straighten it to acceptable limits.

    Paolo

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    Quote Originally Posted by paulymorph View Post
    Here's a video I put together to explain the problem. The high level written description is as follows:
    Wells-Index spindle runout problem - YouTube


    The TIR on the outside lower body of spindle is reading .002-.003 runout
    The inside of the R8 Taper is also reading the same .002-.003 runout. High points and low points are the same on the inside and out.
    Above the taper inside the spindle, the TIR is consistent at .0002-.0003 (2-3 tenths). This is roughly in spec for the machine.
    The taper isn't making uniform contact around the circumference of the collet.
    I'm considering attempting to setup and grind the taper similar to how Shadon HKW did in his YT video.
    R 8 Spindle regrind - YouTube




    I did not crash the spindle. I've had the machine just over a year and as far as I can tell, it's been this way since I got it. It's almost as if the spindle was manually ground previously and was ground off center by the 2-3 thou i'm seeing now. And potentially the outer body of the spindle was reground at the same time which could be why the runout is the same on the inside of the taper and the outside of the body at the same spots.

    Any thoughts or suggestions welcome.
    You may want to watch this video, just for your information.

    https://youtu.be/CFAkb93_V3M

    Charles

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    Quote Originally Posted by JS View Post
    Why don't you just call them? They build the machines and do repairs....
    Oh, I know the gang by first name at Wells. It's a matter of not asking for too much free advice. And this problem would be rather involved to explain. But I may give them a call to get an idea of the price to send the spindle to them for a regrind.

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    Quote Originally Posted by CBlair View Post
    You may want to watch this video, just for your information.

    https://youtu.be/CFAkb93_V3M

    Charles
    Thanks Charles. Funny, that's the video I posted in my original message. :-). I've watched it numerous times and definitely considering. I just need to quit being a chicken.

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    If I were you I would pull the spindle out and check it in V blocks as Paolo mentions. I agree with him. To make sure it is not bent. Check the spindle bearings and see if the quill is straight too. It could be someone installed the bearings wrong and the TIR of the spindle and bearings were installed backwards and doubled the error. There is a * burnish mark on the bearings that means that the bearing TIR is there. It is set at 90 degree's of the spindle TIR. The spindle bearings could be loose too. I always say "never assume anything" and prove it. If you spend another day investigating you may save time and money in the long run. If there is a problem with the spindle or bearings, your screwing something up worse then it is.

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    Quote Originally Posted by paulymorph View Post
    Thanks Charles. Funny, that's the video I posted in my original message. :-). I've watched it numerous times and definitely considering. I just need to quit being a chicken.
    Doh...missed that one, I guess I should have read the whole thing. Hope whatever you decide works for you. Let us know how it all turns out.

    Charles

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    I had about a year of work into a controls retrofit of an old Hurco KM3 mill when I discovered that the spindle had been crashed previously. I ended up sending it back to the manufacturer, Universal Engineering, for a regrind. They ground out the taper, plated it up, ground it again to size, exploded a wheel doing the final grind, and so did the entire process over again. But TIR on what I got back was down in the tenths when measuring on vee blocks.

    However, when I reassembled it and tested in the machine, I got 0.0025 TIR (!). So I tore it down again, put it back on vee blocks, and again, near-perfect. It turns out Universal uses a fixture clamped around the spindle in their grinding setup. They don't have a bearing stack on the spindle when they grind. A couple of rounds of reassembling and disassembling later, it turned out the shoulder near the taper where the bearing stack starts was distorted from the crash by a couple of thou. With no bearings pushing against the shoulder, the taper was on the same axis as when it was reground. But the bearings pushing against the distorted shoulder induced a slight bend in the spindle, and the resulting runout. I took a tiny cut off the shoulder between centers and did a little stoning to fine-tune and the problem went away.

    I mention this experience because it caused me *so* much work before I diagnosed it. If you're measuring, don't assume any of the critical surfaces are correct. I hope you get yours sorted quickly.

    Chris

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    we use this company when we have a spindle taper that is worn but bearings are still good.

    On Site Spindle Taper Grinding and Your Spindle Repair Resource

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    Absolutely remove the spindle and do a full inspection. That's the only way you're going to know exactly what's going on. Check TIR of all the bearing fits as well as the shoulders/faces.

    And who made that collet? As already noted by several of the guys, I'd be awful wary of using a flexible collet to check taper fit. Using a solid shank made by a reputable company would be a lot better. Checking against several different ones would be even better yet.

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    I did this. Regrinding spindle taper on VN 12

    post 24 is the meat of it. set up described in earlier posts.

    First- is this a low use or hobby machine? How accurate does it have to be?
    How much is it worth? Pulling the spindle may be more effort and cost than the machine warrants.

    There is a pretty complete description of how I ground the VN 12 spindle in the link-
    Judging by the condition of the taper, and fairly small runout, I don't think you have a thing to lose. It needs to be fixed, and if you screw it up, it still needs to be fixed, and if the entire spindle is bent it Still needs to be fixed-grinding three thousandths out of it will make no difference if it needs to come out anyway. JMO.

    I used a crappy old makita die grinder with a secure mount and a dressed stone.
    The error/runout in the grinder will average out on the turning taper.

    Get the grinder solid, get the angle right, start real light and take light passes.
    Stop when most of the bluing is gone and the sparks stop. Reassess as necessary.
    Almost all the guys on this forum know way more than me, but I was able to pull it off.
    And yes- do not use a collet to check it-too much flex- use an accurate end mill or shell mill holder.

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    Pulling the spindle on a turret mill doesn't take long at all. IMO there's no excuse not to. If the spindle is bent, depending on how badly it is bent it may wear the bearings out pretty quickly because they will be unevenly loaded as the spindle rotates. Personally I would strongly advise against just grinding the spindle I.D. without disassembly and inspection. It's a pretty small investment in time.

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    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????


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