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  1. #1
    Join Date
    Jul 2011
    Posts
    400

    Spindle Runout.

    I have some tight tolerance work coming up and will be using some very small end mills. I measured my run out on the spindle and its .001". For a new machine with not a lot of hours on it this seems like a bit much to me. I measured the inside of the spindle taper with a dial indicator for the first measurement. Then I measured about 1" from the spindle using a carbide rod in a tts holder. Run out remained the same. If I side load the spindle (light push by hand) I get about the same amount of indicated flex. So my question is how much is beyond normal. Is it adjustable in any way?

    Maybe I'm being too fussy. Have any of you guys checked your run out and if so what did you find?

    Tom

  2. #2
    Join Date
    Jan 2016
    Posts
    386

    Re: Spindle Runout.

    Tom, what machine do you have?

    Steve

  3. #3
    Join Date
    Jul 2011
    Posts
    400

    Re: Spindle Runout.

    A Torus Pro.

  4. #4
    Join Date
    Dec 2009
    Posts
    594

    Re: Spindle Runout.

    That is a lot higher than it should be. Does it vary with RPM?

  5. #5
    Join Date
    Jun 2008
    Posts
    1082

    Re: Spindle Runout.

    I started a thread where I was attempting to reduce my runout by filing down the R8 collet. In that thread I said I was getting about 0.00025" of runout right at the taper.
    http://www.cnczone.com/forums/novako...ce-runout.html

    I'm also curious about how much deflection is acceptable when pushing on the head. I don't remember any numbers, but I remember being surprised about how much it was. I also see Don Baiely (from Suburban Tool - YouTube channel: https://www.youtube.com/user/SuburbanToolInc) pushing on machines all the time to make a machine cut just a tiny bit more.

  6. #6
    Join Date
    Jul 2011
    Posts
    400

    Re: Spindle Runout.

    For Kvom. I'm measuring it while turning the spindle by hand. It seems that the taper in the spindle itself is out of round. I did the testing with 2 different R8 collets got the same result both times.

    Tom

  7. #7
    Join Date
    Feb 2006
    Posts
    7063

    Re: Spindle Runout.

    A grinding shop can re-grind the taper, and it's typically not terribly expensive.

    But, using tiny endmills on a machine with a 6KRPM spindle is probably not going to go well anyway. You should seriously consider adding a high-speed companion spindle. They're not terribly expensive these days, and will VASTLY speed up work with small tools.

    Regards,
    Ray L.

  8. #8
    Join Date
    Jul 2011
    Posts
    400

    Re: Spindle Runout.

    I did a little calling around to see if I could get it reground locally. No one wants to touch it. I think at some point maybe the spindle will make a trip to the usa. Tightening the screws on the bottom of the spindle has reduced the runout a little.

    I also played around a little with different positions between the tool holder and the collet. One that I remember varied from .0005 to .003 Depending on where it was. Most of the others I tried were closer or at least did not have the large variation. I have seen some suggest a dot of paint to make sure the tool always goes in the same position. I'm thinking that might be good advice.

    The high speed spindle Ray mentioned might be in the future. For now i don't have nearly enough volume to justify it.

    Tom

  9. #9
    Join Date
    Jun 2008
    Posts
    1082

    Re: Spindle Runout.

    Have you put any thought into grinding the spindle yourself? It doesn't look... impossible.
    https://www.youtube.com/watch?v=CFAkb93_V3M

    It would probably be a mistake for me to try this, but I might do it anyway if I needed it to be done and I couldn't find any professionals (or they all wanted too much money).

    Indicating the spindle would be difficult. I'm thinking it might be possible to establish the 8.425º (that's what he said, right?) angle by indicating against a sine plate at the same angle off the table. Basically, you'd be tramming the head, but the reference surface would be a sine plate instead of the bed.
    All I know is that I hope I don't have to make this choice for a long time!

  10. #10
    Join Date
    Jul 2011
    Posts
    400

    Re: Spindle Runout.

    That video on a DIY spindle grind looks interesting. I think that would be a last resort though. I think I'm going to send an email to Novakon to see what they think. I'm going to hold off on doing that for a little bit until they get settled in their new location.

    Tom

  11. #11
    Join Date
    Jan 2007
    Posts
    1795

    Re: Spindle Runout.

    in my opinion, and in order with expenses...

    first try some new collets.. ... mightbe that solve it already...

    next compare the regrinding price with a new spindle,,, I don't know the regrinding prices, but a new spindle is just new,,


    also you can consider a small water cooled spindle, you can get for about 250...

    65mm 0 8KW ER11 Four Bearing Air Cooled Motor Spindle and Inverter Drive VFD CNC | eBay

    endmills under 2 mm dia... need high rpm... under 1 mm sure the 5-6K rpm your machine does right now, just way too slow..

    datron using 60K rpm spindles for metal.. so the 5-6 K rpm sounds really slow..

  12. #12
    Join Date
    Sep 2006
    Posts
    6463

    Re: Spindle Runout.

    Hi.....one point to be made when grinding ANY bore.....always use a sacrificial plate at the entrance to the bore or you'll get bell mouthing as the grinding wheel enters and leaves the bore.

    Second point......never use a stone wider than you need or you'll get more grinding at the front as you go deeper into the bore, and a deep groove in the centre when the stone stops moving forwards and is reversed out

    Third point.........to fit a sacrificial plate to the front end of the spindle bore just epoxy resin glue it to the spindle bore front and remove it afterwards by heating it gently.....Epoxy resin will go soft at about 200 to 400 deg C.

    Normally you grind with the stone going against the direction of the spindle rotation not with it, but if the spindle is rotating slowly this is not all that important.

    Fourth point......the stone centre must be on the same centre line height as the spindle or the taper angle will be different.

    Last point............don't use a stone too fine a grit or you'll glaze the stone and it will just rub and make burn marks in the bore instead of grinding it........the stone should be dressed in position with a diamond dressing stick held in a holder....NOT HAND HELD...... to replicate the same angle as the taper to be ground.

    When you want to get the results to "improve" the existing ground bore....as the man says, you only get one maybe two chances at most, so set up is of prime importance.

    In a case where the head cannot be swung over or is fixed, like in a column mill, removing the spindle housing or a quill is an option that can be done too but is a bit more involved than this method.

    If you get really really desperate, stripping the spindle shaft out of the spindle body and running it in a lathe with the splined end in the chuck and the R8 bore end held in it's bearing in a lathe steady will work too, but needs some skill and patience to achieve as you're hand working with the compound slide.......an electric screw driver also makes this easier as it's reversible and slow.

    I used an angle grinder (10,000 rpm ?) with an adaptor to hold mounted stones for grinding out collets in situ for a capstan lathe many years ago.
    Ian.

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