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  1. #1
    dkmc is offline Diamond
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    Default VMC Spindle kaput.....after recent replacement...mystery...

    First, I am asking this with little info on situation.
    Only relating what I have heard, don't expect astounding revelations, but PM members have astounded me in the past more than once!

    VMC with spindle that "quit"......
    Recently replaced...Drive? ....no... spindle cartridge.

    Green button guy:
    "Worked fer awhile then quit agin"....
    "An dares shiit leakin out of the thing dare"...

    Evidence: Spindle has about a 1/2" diameter "wad" or "ring" of green grease around it where the inner turning part runs close with the outer stationary part. (Near the bottom, near the drive dogs)

    Question: What could happen to the new spindle that would cause it to fail this way in.....say......2 weeks or 30 days?

    Too much grease?
    What is the effect of tooo much grease on an 8000 RPM spindle? I don't know if it still turns, which would say alot, but didn't want to appear... too interested. If you know what I mean....

    Speculation?
    Theory?


    No....not a puzzle....you don't have to build a propeller shaft for a cruise ship with an angle grinder and a pipe wrench......

    dk

  2. #2
    J Henricksen is offline Stainless
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    Default

    Not much to go on to even guess. Does the thing even turn on? spindle turn by hand? How does it feel when you turn it? Coolant union could have failed and leaked into the bearings, could be too much grease. Might be a bad motor overload... lots of might be's here. What was the finish like just before it quit?
    Too much grease will tend to run hot until the excess has worked out of the bearings and bearing cavity. There is probably just a labyrinth seal at the bottom. (Non contact seal maybe with air purge.)

  3. #3
    ARB's Avatar
    ARB
    ARB is offline Titanium
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    Too much grease can be as bad as not enough. Do you know if this was rebuilt by an experienced spindle rebuild service? Or did someone through in some new bearings and some wheel bearing grease?:rolleyes:
    8000 RPM is getting fast enough for things to matter that they are just so.

    On edit.

    What make and model machine and control?

    Were there any tell tale alarms?

  4. #4
    Rich Carlstedt is offline Stainless
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    For my two cents, if you have grease oosing out , on a 8,000 RPM spindle, its a sure sign of over packing. OR no venting of the spindle. some have vents, some don't.
    Usually the upper bearing is not under load, like the bottom, and had less grease, and air can get out there.

    You should have noticed it on running, as it gets hot , Also, you will see your depth of cut change as the spindle gets longer..what was QC like during that period ?

    Rich

  5. #5
    dkmc is offline Diamond
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    Default

    Well, youz guys have done real well wit the little info I have provided.....so far.

    I will 'dance around the issue' in days to come and see if it does indeed turn still. I hope to maybe post a machine gloat here in the future but am holding breath and turning light sky blue at the moment. Being a bit superstitious, I hate to jinx deals with pre-gloats.

    Machine name begins with R and control name begins with C. Who would think I'd be.....

    staie tuned...

    dk

    PS QC.....?? this place is a relative "cave" with abrasive wheel and stone ax......no QC exists...I don't see a surface plate.

  6. #6
    machtool is online now Titanium
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    If it has enough grease in it to produce a ½” cord or wad of grease, and that’s what you can see at the labyrinth, it’s most certainly over packed.

    Roughly speaking with a few wild guesses through in for good measure. Assuming Cat 40 size spindle @ 8k, most bearings I put in would have 4 – 6 CC’s of grease. Its bugger all to look at. And now where near enough grease to produce that amount of wash out.

    The other thing I note. GREEN. I’m not aware of any of the special high speed spindle greases that are green. Whites, browns, creams, yellows, but never green.

    Assuming it was over filled, it should have been running hot due to the churning. On really over packed bearings the stress can cause the cage to crack, that will cause a pretty instant failure.

    Regards Phil.
    Last edited by machtool; 02-21-2008 at 05:11 AM. Reason: Spelling

  7. #7
    macona's Avatar
    macona is offline Diamond
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    Isnt kluber grease green or blue?

  8. #8
    dkmc is offline Diamond
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    Isnt kluber grease green or blue?
    My tube shows creame (light tan) color
    Kan dis be as simple as a blowed fuse??

  9. #9
    bryan_machine is online now Titanium
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    "Kan dis be as simple as a blowed fuse?? " - sure, depending on what alarms the machine has. But what caused the fuse to blow?

  10. #10
    dkmc is offline Diamond
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    .....and he shall investigate....

  11. #11
    machtool is online now Titanium
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    Isnt kluber grease green or blue?
    Not that I’ve ever seen, and I go through a lot of it. Color is important to me, a hint of that I can tell what was originally put in an assembly.

    I keep ever thing here from Staburags NBU- 8 EP – beige, for low speed - high load applications to stock in trade Isoflex NBU 15 & NCA 15 – white for most angular contact run of the mill or fast run-in stuff, and Isoflex LDS 18 Special A –Yellow & Klüberspeed BF 72-22 – Beige, for high speed and integral spindle motors.

    Timkin’s high speed spindle grease is a light yellow / amber. Fag’s Arcanol range L75 etc are all pale colors.

    Having said that (I’ve never seen a Green spindle grease) which is true, because I’ve never used this. I had a wade through a Barden precision catalogue, on the assumption that if the cartridge was reconditioned, Barden would be the preference.

    There is one grease that is green, they (Barden) specify it as G-74, its actually Exxon Unirex N3. IMHO it is numbered very poorly by Barden. The numbers run from G2 –(Exxon Beacon 325) thru G75 – (Arcanol L-75). Looking at the table, you would think G-74 was the second highest rating grease. Poor old Kluber NBU 15 has the lowly rank of G-46, yet it’s the most widely specified grease in this application.

    http://www.exxon.com/USA-English/Lubes/PDS/GLUSENGRSEXUnirex_N.asp

    That might explain the green if they purchased Barden bearings and one of the recommended greases. Doesn’t explain why there’s half a cup too much oozing out of the bottom of the spindle, or how much damage it’s done in the process.

    Just an observation on the Unirex N3. It is an NLGI # 3, which is normally considered heavy for high speed spindle use. It also has mean speed rating of only 360,000 min.

    {Quote from the above link} “Unirex N3 is recommended where DmN (mean bearing diameter X rpm) exceeds 360,000.” It doesn’t list a high limit. And 360k would be considered very low today.

    For reference, the Kluber NBU 15 goes to 1,200,000, the BF 72-22 are claiming figures of 2,000,000 DmN. Speeds that used to be reserved for oil-air-mist lubrication.

    Speed mean or DmN figures are the easiest engineering calculations on earth. It’s a simple factor of the average of your bearing diameters multiplied by the maximum speed, to come up with a factor. Yet another W.A.G, assuming this is a 40 taper machine. By the time you stuff a 40 taper into the spindle, and leave a little meat for the spindle journal. You normally end up with a 60mm bearing I.D journal. 65mm is also common. Its only 8,000 r.p.m, so no need for exotic series. You would normally find an ISO 70xx series bearing. So 60 I.D x 95 O.D x 18 thick, making it an 7012 bearing Average bore of your 60 + 95 = 77.5 multiplied by your speed (8,000) = a DmN of 620,000. That’s just under double the 360k recommendation of the green grease.

    In summary.

    They rebuilt it with a recommended lubricant that was border line on speed capacity.

    They shovelled it in, if it’s welling up at the bottom like you describe.

    Or they bought the pretty green grease at Napa, and packed it full like they used to do for wheel bearings

    Either way, you can count on pulling the spindle down for inspection.

    Regards Phil.

  12. #12
    wippin' boy is offline Diamond
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    wish you were in my backyard mach

    i'm with someone thought he had boat trailer wheel bearings on his hand

    sounds like you could do about 15 cat 40's with what has washed out out the laberanth coller

  13. #13
    dkmc is offline Diamond
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    Guys, I need to clarify that I saw the ring of grease from a closest point of about 3-4 feet away, not dark but not with a shop light shining on it either.

    SO....maybe it's not actually ....green.
    Maybe its other color that's contaminated.....?
    I will obviously look if things pan out.....

    My impression is they "had someone replace the spindle" .....gawd you wouldn't let these shop people get into the thing or they -would- do the NAPA cartridge pump-er-full trick. Although, someone else may have, it's oozing something!
    OTOH, it 'sounds' like a sorta easy fix...I hope.

    Also, (I am) learning good things about bearing greases and bearing engineering!
    Thanks!

    dk

  14. #14
    macona's Avatar
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    For some reason I though that stuff was blue.

    I ordered some new A/C bearings from BPT for the ball screws on my machine and the stuff was blue. Maybe thats why I got it confused.

  15. #15
    Hollistergc is offline Hot Rolled
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    Gee, kinda sounds like someone crashed the spindle. Dripping is coolant? Ring is coolant mixed with grease? Does the machine have TSC?

    Used to GET this kind of thing quite frequently. "Spindle just failed". But when you took it apart you could see the directional burn mark on the end cap and almost always had coolant saturated bearings.

  16. #16
    split tenth is offline Cast Iron
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    Greased bearings should only have enough grease to fill one third (1/3) of the void area.Micro filtered grease from bearing manufacturer not some axle grease from the corner auto store. If over filled with grease the balls will want to plough and skid destroying balls and races.A rebuilt spindle needs to be broken in on start up by running first at slow speed and gradually increasing the speed a little at a time closely monitoring spindle temperature.If it starts to get hot shut it down let it cool.It sometimes takes me about an hour to reach top speed. Start over again with slow speed.DO NOT push the spindle start and run at top speed.I can't tell you how many times I've seen bearings completely full of grease and then destroyed with full speed start up.You may also want to pull spindle apart to check for proper orientation of angular contact bearings, proper high pointing,and excess grease.Do this in a clean area of your plant,(clean room, lunch room, office,)Don't laugh, I've seen spindles rebuilt on surface grinder saddles.Contamination from dirt,or tools is now a big problem.

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