SB13 spindle bearing oil film.
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  1. #1
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    Default SB13 spindle bearing oil film.

    I use my SB13 for (among other things) gunsmithing. One common task is to align the bore of a barrel with the spindle bore. There are a few different ways to do this, like inboard and outboard spiders, but in the end, you are checking the runout of the bore in tenths of thousandths.

    I've noticed that the oil film on the spindle bearing will run out fairly quickly. You can watch it happen with a tenth DTI. you spin the chuck a few times and get a nice coating on the journal and bearing, then when the spindle stops, you can watch it slowly drop as gravity forces the oil film out. My bearings are shimmed to spec and the oil is fresh and new.

    I'm wondering if anyone has ever used a viscosity enhancer like STP in the spindle bearing sump or some other method to try and keep a decent amount of oil film on the bearings for a longer period of time.

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    I don't think that STP would allow it to wick properly through the oil wicks. Also, the spindle bearings call for a light oil and would probably run warm at the higher speeds due to the oil drag.

    Just my $.02 worth....

    Frank

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    Just my opinion but if you expect to set up with 0.000# accuracy and maintain that when running and with cutting forces then a plain bearing lathe is not the correct choice.

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    Just don't try and do any machining without the spindle turning, problem solved When attempting to turn to tenths the cutting pressure on final passes are usually negligible unless you are trying to hit in in one pass

    Paul
    Last edited by SpringGunner; 07-10-2014 at 04:22 PM.

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    Or figger out what the difference is between spinning and resting. It should come out the same or real close to the same every time and compensate by dialing your machine up accordingly. Another choice would be to indicate it in accordingly with the spindle spinning. It's all part of knowing your machine. I have never checked this on mine as I haven't needed that kind of accuracy.

    Also if the difference works out to only be small fractions of a tenth, is it really worth all of the bullshit to get it on dead nuts? ? ?
    Do you really need that kind of accuracy? ?

    Frank

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    Quote Originally Posted by SpringGunner View Post
    Just don't try and do any machining without the spindle turning, problem solved When attempting to turn to tenths the cutting pressure on final passes are usually negligible unless you are trying to hit in in pass

    Paul
    If he's working with something like 4140, you can't easily fuzz cut that stuff, the finish will look like shit. You have to take some meat off or it just comes out with a terrible finish. You need to be making chips and not fuzz even for your final cut.

    Just my $.02 worth.....

    Frank

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    The oil film is still there. If you don't believe that, put the dial gage on the spindle. Then stick a broomstick
    in the bore and push down. Zero the dial, then pull up.

    That's the clearance. The spindle will settle midway between the extremes.

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    Quote Originally Posted by jim rozen View Post
    The oil film is still there. If you don't believe that, put the dial gage on the spindle. Then stick a broomstick
    in the bore and push down. Zero the dial, then pull up.
    Yeah, that's how I adjusted the bearing shims. I shimmed it to the tighter end of the spec but don't get any bearing heat above normal.

    Quote Originally Posted by jim rozen View Post
    That's the clearance. The spindle will settle midway between the extremes.
    It seems to settle about 2 tenths from spinning the spindle by hand to get the oil film established, and waiting about 5 seconds after letting it coast down. I'm sure that under power, it will have a solid oil film and deflection will be negligible, it just makes it more difficult to dial in.


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    Quote Originally Posted by KB3AHE View Post
    If he's working with something like 4140, you can't easily fuzz cut that stuff, the finish will look like shit. You have to take some meat off or it just comes out with a terrible finish. You need to be making chips and not fuzz even for your final cut.

    Just my $.02 worth.....

    Frank
    4140 is tough to work with. With a CCMT 32.51 I need at least a 0.025 DoC. If I miss the mark on the final cut, I'll cut a thou or two with a VNMG 330. The finish is still pretty horrible, but it cleans up with a file and some wet-or-dry soaked in WD40.

    I like 416 stainless a lot more. It will take a light cut with a CCMT 32.50 and still give a usable finish--good enough to followup with threading.





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