Spindel issues : replace / repair / move-on?
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  1. #1
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    Default Spindel issues : replace / repair / move-on?

    A few months ago I got my first VMC and most things seemed to check out okay, for it being an older machine ('99).

    The dial showed that inside the spindle taper had almost no run out - or so I thought at the time. Fast forward to a few weeks ago and I started breaking my smaller drill bits faster then I could get new ones (1mm and 1/16"). The tool paths f/s checked out as I've run them before on different machines. Checking the run out at the end of the tool and I was all over the map. I figured it was the cheap import tool holders so I got a bunch from Maritool.

    I continued to break even more drill bit.

    It turns out that when I indicate the spindle taper beyond the first 1/8" into the taper everything is perfect. BUT the outer edge of the spindle taper is jacked up.

    My new drill chucks are showing a consistent 0.003" run out along the entire length of several tools. (I even tried putting the check tools into the spindle 'backwards'.) It's consistent.

    I need a lot of small drills and end mills.

    Is there anything I can do to reduce or repair this run out? Or is it time to stop wasting time and look for a new machine? (If so, how the hell do you get rid of a VMC with 3thou run out?!?!)

    Thx.

    PS A machine this old - and has given me this many issues - is not likely to have the spindle 'replaced' so that's not an option but I should get a quote from Mori just to see.

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    First you need to clarify what exactly is wrong. I can't be sure from your description, but it sounds like there's damage at the nose of the spindle that intrudes inward towards the taper geometry. If correct, this means the toolholders never seat properly, and can rock and displace the cutter/drill from spindle centerline.

    If this is what's going on, and otherwise the spindle bearings and taper are OK, then just removing the protruding material at the nose of the taper should allow correct seating of the toolholders. Not optimal from a "total support" of the taper standpoint, but with a machine that old it's good enough.

    If this isn't what's going on, you have to do a better job of describing the actual fault mechanism, which could be bad bearings, material further inside the taper preventing correct seating, or other failure mode.

    Please try to restate what's not working properly.

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    What type Mori do you have?
    how do the bearings sound?
    If you do end up doing autopsy just member bearings need to be tested under load. It gives me willies every time I see a guy pull apart a bearing assembly give 'em twist a say these are good. Pet peeve.

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    I think the first thing you could do is blue up a decent tool holder and see how it seats in the spindle. If when you say 'jacked up' you mean theres high points near the face of the taper, you should be able to lap those away easy enough. Check the spindle bearings for slop with a 12" bar mounted in the spindle, indicate the nose of the spindle while pushing and pulling on the bar and see what you get.
    Its not rocket science, just take it one step at a time and youll get to the bottom of it, then you can make the decision.

    Cheers
    D

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    What taper? There's a few things that could be happening depending on what taper the spindle is. Checking run-out inside the taper can be deceiving, i'd invest in a good test bar for future reference (Command or TAC Rockford).

    If it is a CAT/ISO taper I would recommend contacting a spindle grinding service. The cost is very inexpensive compared to a new spindle. I use Catt Spindle Grinding Service, when they come out they inspect the spindle with a test bar, dynamometer and a custom positive pressure master tool. It usually takes them around an hour to have that thing within 0.0005". Of course, this number will depend on any bearing deflection you may have in your spindle.

    If it is an HSK taper, some spindle grinding companies can also clean them up. It's just not as promising as the Cat taper. Catt Spindle Grinding Service also offers this service, although they are out of MI but they do a great job.

    Another option is to have the spindle rebuilt which will be a fraction of the cost but this option will take 2-4 weeks easy and you have to do some investigating to make sure you use a company that will stand behind they're work.

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    There a people that can recut the taper ( if thats the actual issue ). I believe there.was one on here. There was a guy around here that did it but sadly he passed away. Worse case scenario there are guys that have recut it themselves in the machine, doesnt look too hard though Im not real sure I would attempt it myself.

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    I can't be clear from the description, but if you are not describing high points in the spindle taper mating surface with the toolholder, are you describing a tram issue? Where the spindle isn't perpendicular to the table? Trying to understand what you mean by "jacked up"

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    Quote Originally Posted by Bones288 View Post
    A few months ago I got my first VMC and most things seemed to check out okay, for it being an older machine ('99).

    The dial showed that inside the spindle taper had almost no run out - or so I thought at the time. Fast forward to a few weeks ago and I started breaking my smaller drill bits faster then I could get new ones (1mm and 1/16"). The tool paths f/s checked out as I've run them before on different machines. Checking the run out at the end of the tool and I was all over the map. I figured it was the cheap import tool holders so I got a bunch from Maritool.

    I continued to break even more drill bit.

    It turns out that when I indicate the spindle taper beyond the first 1/8" into the taper everything is perfect. BUT the outer edge of the spindle taper is jacked up.

    My new drill chucks are showing a consistent 0.003" run out along the entire length of several tools. (I even tried putting the check tools into the spindle 'backwards'.) It's consistent.

    I need a lot of small drills and end mills.

    Is there anything I can do to reduce or repair this run out? Or is it time to stop wasting time and look for a new machine? (If so, how the hell do you get rid of a VMC with 3thou run out?!?!)

    Thx.

    PS A machine this old - and has given me this many issues - is not likely to have the spindle 'replaced' so that's not an option but I should get a quote from Mori just to see.
    A 99 Mori should have a ceramic spindle liner right? I don't think I would use a drill chuck if I wanted low runout on my drill. I don't own a cat-40 drill chuck (maybe that's just me?)but I drill lots of holes.

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    I have never had a taper ground in place but I have pulled spindles to have the taper ground before. I just had a spindle in my 2001 mill rebuilt right so don't think it isn't a good option if the rest of the machine is decent. Setco in LA can do whatever you need, either a full rebuild or just grind the taper, and it will be done right. I would guess a taper grind would have a couple day turnaround for a couple hundred $, less if you want to pay extra $$. Being the mouth of the taper you DO NOT want to relieve it so there is no contact, that would be butchery.

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    Thanks for all of the feedback and EVERYONE is right: my description is lacking.

    Limited 'real' VMC experience and 8 hours of spotty sleep in the last three days is taking it's toll.

    The only thing I can find that could explain why all of my small bits are breaking is the 0.003" run out.
    And the only place I can find why the bits would be walking that far is the ~0.0025" high point just inside the lip of the spindle nose (not the face, sorry).

    And CAT40 taper for my CV-500a.

    So it sounds like I'm not looking for a) spindle taper test bar, and b) grinding service to at least come in and take a look.

    I didn't expect so much feedback this quickly and I seriously appreciate everyone's input. This has likely just saved me some major $$$.

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    Start with photos of you bluing a taper, use one of Franks. It sounds pretty simple. You don't need a test bar. The runout is your tool problem, and the high spot isn't good for your tool holders.

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    Quote Originally Posted by DavidScott View Post
    Start with photos of you bluing a taper, use one of Franks. It sounds pretty simple. You don't need a test bar. The runout is your tool problem, and the high spot isn't good for your tool holders.
    Ah yes, I forgot one: c) blue the taper for contact testing. Thx for the reminder. I'll pick some up now.

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    I've ground the spindle taper in place with an air powered high speed spindle thingy and was surprised how well it worked out. Similar situation on an older Mori.







    I figured I'd need to pull the spindle and send it out for some love but I'd try it myself first. I was pleasantly surprised. Not only did the runout fall to a few tenths (within my ability to measure it) it has held up over time and it the tool holders are fine. This is a 14,000 RPM 30HP spindle.

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    Yep !! Awesome. Thats how you do it. I wish more people would think out of the box and do this. If done right spindle will just as accurate as from the factory. Ive done 30, 40 taper many times. Both with CBN inserts in a boring bar and grinding like this.

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    I remove the drive keys if possible, always (unless a HAAS). One less thing to worry about. Can choke up on the boring bar or grinding shank shorter.

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    Quote Originally Posted by fmari --MariTool- View Post
    Yep !! Awesome. Thats how you do it. I wish more people would think out of the box and do this. If done right spindle will just as accurate as from the factory. Ive done 30, 40 taper many times. Both with CBN inserts in a boring bar and grinding like this.
    Frank do you have any quantifiable numbers on runout and contact results? In general this a subject that I feel would be very good to explore and explain on the forum so people feel comfortable taking measurements and quantifying their "improvements".

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    Runout. Zero. If done properly and spindle bearings are in good condition I am able to get .0001 tir 6" away from gage line. Grinding or CBN.

    No trick to it. Just a lot of patience and alcohol (no not for drinking hahaha). Between grinding or CBN boring passes you need to blow out chips via drawbar ejection. Wipe the spindle taper with alcohol wipes. Let dry. put some blue on the test bar taper. Clamp and look at your contact pattern.

    Let me say something about Prussian blue. I see a lot of pictures on how people are using it. If the blue shows on the camera, you used twice too much !! I use a thimble for the entire taper. Actually I do the full length about 30 deg worth, not the whole taper, not needed.

    While tweeking contact don't even worry about the tir. That you worry about later. Once contact gets better you leave it and do a few spring passes. Then see how the contact is.

    When you are done I rotate spindle 300 rpms and wrap fine scotchbrite around my finger. Then I go back and forth in the spindle just to remove any glaze or record player pattern ( if boring). If you know what you are doing it is maybe a 2-3 hour job tops.

    If spindle is really buggered, once you remove the crap welding or damage replace the insert for a fresh one. If grinding, redress the wheel after spindle is looking flat. Hope this helps.

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    The folks that grind spindles in place as a biz have their grinder on its own set of ways. This eliminates the condition of the machine from introducing error in the grind.

    I've had decent results using the machine to grind itself when...

    1. The machine is in good shape. An old VMC with a droopy head is not a good candidate because the spindle centerline is not parallel with the Z axis. If one has to do a machine like that, you'll get a better result if you grind using the Y and Z axes for the taper. Most folks tend to do this in the X and Z axes which will give a bell-mouth taper

    2. The grind program is uni-directional. In other words, not cycling back and forth, but making a "loop".

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    I have a grinding unit. It has its own reciprocating cylinder with a NSK air grinder in it. Just give it air and it moves in and out while grinding. I will post a picture once I am in the shop. I will never sell it. Awesome unit. Looked everywhere for another unit, can't find it. I got in on Ebay maybe 12 years ago for a steal. I think it can traverse in and out 3.5 or 4". It is adjustable from 0-max travel.

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    I figured my entire problem was due to sloppy import tool holders so the way I checked against this was a large (for me) Maritool order. I received the first part of my order and threw them into the machine immediately. That's when I got my nasty surprise that it's likely the spindle itself. Two of the three chucks measured the exact same and I didn't bother trying the third.

    When my family is done with this sickness I'll test my test setup on a neighbors Haas. But I'm certain it'll be better than the flapping that's happening in my shop.

    Since I can't take a chance on messing this up right now, what is the ball park cost range of having someone come in and regrind the spindle? I have some feelers out now but am waiting to hear back.


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