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IndustryArena Forum > CNC Electronics > Spindles / VFD > Spindle bearing upgrade question
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  1. #1

    Spindle bearing upgrade question

    Hey guys, I’m sure this topic has been beat to death, but I’m not finding the exact info I’m looking for. But I just finished retrofitting my cnc, and while I’m in the flow of upgrading everything, I’d like to replace the tapered roller bearings in the spindle to something like angular contact bearings so I can run the spindle at a slightly higher rpm since I’d prefer to use carbide endmills wherever possible. The max rpm my machine is currently rated for is 4000 rpm which obviously a bit low for a lot of carbide, so I’m wondering if changing the bearings will allow enough of an increase in rpm to be worth going through the effort of rebuilding the spindle? Or if I should even attempt an “unnecessary” spindle rebuild, because I’m aware of the hazards associated with precision spindles and contamination. So question 1, is it worth the risk/hassle to rebuild a perfectly good spindle? Question 2, are angular contact bearings the correct choice for my application? And question 3, how much faster could I potentially run my spindle if I do replace the bearings? In case these factors have an effect, the head of the mill is like the vari-speed Bridgeport heads. It uses a belt drive to a “bull gear” I guess you’d call it, to spin the spindle gear, which has a hi/n/lo selector. But I change rpm through the vfd, not the varispeed controls Any info would be appreciated. Thanks !

  2. #2
    Community Moderator Jim Dawson's Avatar
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    Re: Spindle bearing upgrade question

    It is unlikely that you have taper roller bearings in a 2J2 style spindle. Every one I have seen has angular contact bearings as original equipment. The original veri-speed is limited to about 4200 RPM due to the mechanics of the system. I'm not sure how much speed the front pulley will take before risk of it coming apart at high RPM. I put a direct drive in mine and can turn 6000 RPM, 1.3:1 ratio, but I rarely turn it that fast, normally around 3200 max. I find this is fine even with carbide endmills, I just cut the feed speed back to match the RPM to keep a proper chip load.

    If I really need high speed for tiny endmills, I have an air spindle that fits my main spindle and it will turn 50,000 RPM or so.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
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    Re: Spindle bearing upgrade question

    Quote Originally Posted by Jim Dawson View Post
    It is unlikely that you have taper roller bearings in a 2J2 style spindle. Every one I have seen has angular contact bearings as original equipment. The original veri-speed is limited to about 4200 RPM due to the mechanics of the system. I'm not sure how much speed the front pulley will take before risk of it coming apart at high RPM. I put a direct drive in mine and can turn 6000 RPM, 1.3:1 ratio, but I rarely turn it that fast, normally around 3200 max. I find this is fine even with carbide endmills, I just cut the feed speed back to match the RPM to keep a proper chip load.

    If I really need high speed for tiny endmills, I have an air spindle that fits my main spindle and it will turn 50,000 RPM or so.
    It is quite common for these spindles to have Taper Roller bearings; they are a superior spindle over the spindles with angular contact bearings
    Mactec54

  4. #4
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    Re: Spindle bearing upgrade question

    Quote Originally Posted by Codythecreator View Post
    Hey guys, I’m sure this topic has been beat to death, but I’m not finding the exact info I’m looking for. But I just finished retrofitting my cnc, and while I’m in the flow of upgrading everything, I’d like to replace the tapered roller bearings in the spindle to something like angular contact bearings so I can run the spindle at a slightly higher rpm since I’d prefer to use carbide endmills wherever possible. The max rpm my machine is currently rated for is 4000 rpm which obviously a bit low for a lot of carbide, so I’m wondering if changing the bearings will allow enough of an increase in rpm to be worth going through the effort of rebuilding the spindle? Or if I should even attempt an “unnecessary” spindle rebuild, because I’m aware of the hazards associated with precision spindles and contamination. So question 1, is it worth the risk/hassle to rebuild a perfectly good spindle? Question 2, are angular contact bearings the correct choice for my application? And question 3, how much faster could I potentially run my spindle if I do replace the bearings? In case these factors have an effect, the head of the mill is like the vari-speed Bridgeport heads. It uses a belt drive to a “bull gear” I guess you’d call it, to spin the spindle gear, which has a hi/n/lo selector. But I change rpm through the vfd, not the varispeed controls Any info would be appreciated. Thanks !
    Up to 4000 RPM is a good speed for carbide cutters depending on what size cutter you are using, your spindle could run all-day at 5000 RPM and up to 6000 RPM without any problems just the way it is, your Bearings are fine, the varispeed is where your problem will be, because that will have a limit as to what speed it can be run at, when modifying a head like this for higher speed, the vari-speed has to be removed and direct drive is used, a photo of your head would be good
    Mactec54

  5. #5
    Community Moderator Jim Dawson's Avatar
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    Re: Spindle bearing upgrade question

    Quote Originally Posted by mactec54 View Post
    It is quite common for these spindles to have Taper Roller bearings; they are a superior spindle over the spindles with angular contact bearings
    I guess i should have said: None of the machines I have owned or worked on had taper roller bearing spindles, all had/have angular contact bearings.
    Jim Dawson
    Sandy, Oregon, USA

  6. #6
    Quote Originally Posted by mactec54 View Post
    Up to 4000 RPM is a good speed for carbide cutters depending on what size cutter you are using, your spindle could run all-day at 5000 RPM and up to 6000 RPM without any problems just the way it is, your Bearings are fine, the varispeed is where your problem will be, because that will have a limit as to what speed it can be run at, when modifying a head like this for higher speed, the vari-speed has to be removed and direct drive is used, a photo of your head would be good

    My “go to” sizes for carbide (or any endmill really) typically range from .0625 at the absolute smallest to .375. But I do run .500 occasionally and I like my flycutter for finishing ( don’t have the hp for those 6-10 insert facemills). I would have no problem removing the vari-speed, because I never use it It’s set to max speed in high gear and I control the rpm’s with the vfd But I’ll definitely post a pic of the head here in a few minutes ???????? Thanks

  7. #7
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    Re: Spindle bearing upgrade question

    Angular contact ball bearings, precision spindle bearings, there are too many options now, but if you are interested in Chinese suppliers, the relative prices in China are more diverse, and there are more choices, you can choose according to According to your own needs, choose a targeted manufacturer, there are multiple suppliers, different models, different quality and different prices to choose from: https://www.tradebearings.com/precis...catalogue.html

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