Problem bk12 bearing eplacement


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Thread: bk12 bearing eplacement

  1. #1
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    Default bk12 bearing eplacement

    Hey guys,

    I'm going through my second hand router part by part and noticed that one of the screws turned with a wee crunch. I took the bk12 block off and lo and behold some metal shavings fell out and the bearing turns with an arthritic crunch!

    bk12 bearing eplacement-20200924_174054-small-jpg

    Is anyone willing to help a guy out here? I'm a bearing newbie so I'm left scratching my head learning here.
    • how do i get the bearings out? They're stuck fast in there. I've read you can heat the block up to get the bearings out, however there's a rubber like seal one end which I'm assuming is averse to a heat gun/ oven. Before i get the socket and bench vice going to push it out, can anyone give me some tips?
    • The bearing says 7001ac. I'm a bearing newbie, and when I'm in a newbie scenario i tend to replace like for like. I found an apparent exact replacement here, but its from 3 weeks away china. I'm struggling to find a UK supplier with similar markings. Can anyone help me source something similar and more local?

    thanks
    Nic

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    Default Re: bk12 bearing eplacement

    Press it out. Or tap it out. The clearances of the blocks are normally quite loose. Those bearings are as common as chips. When I buy them I buy 10 at a time off the Chinese sites for $20. The markings will relate to the size type and type of seal. Off memory your one is a 30mm x 8mm x 12mm. When you measure it you only need call around and give those measurements to replace it. I would be surprised if you can't find one within 20km of home. B

    Sent from my SM-N970F using Tapatalk



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    Default Re: bk12 bearing eplacement

    Quote Originally Posted by boydage View Post
    Press it out. Or tap it out. The clearances of the blocks are normally quite loose. Those bearings are as common as chips. When I buy them I buy 10 at a time off the Chinese sites for $20. The markings will relate to the size type and type of seal. Off memory your one is a 30mm x 8mm x 12mm. When you measure it you only need call around and give those measurements to replace it. I would be surprised if you can't find one within 20km of home. B

    Sent from my SM-N970F using Tapatalk
    thanks very much. I've emailed a few online shops now in the UK. I'll see if there's someone local to me in bristol too.



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    Default Re: bk12 bearing eplacement

    I'm watching with interest as one of my bearings seems to be heading the same way.The cheering thing is that the bearing business will almost certainly have an answer and if you can find a partsman with really good product knowledge,there is a good chance that you will be able to buy a much better bearing for not a huge amount of money.One of the few useful things about the current pandemic is that the businesses trying to operate are mostly able to give each serious enquiry more serious consideration than in busier times and the knowledge that you definitely intend to buy will encourage that.



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    Default Re: bk12 bearing eplacement

    AC bearings can be purchased as a matched pair from China for very reasonable prices. A fussy youtuber ordered a set with low expectations but ended up surpised in a good way. If I come across that video again I'll link it here, he may have named the supplier.
    Quality individual bearings off the shelf may be close enough to matched but in theory AC bearings should be bought in pairs. In theory as opposed to DIY reality..

    Anyone who says "It only goes together one way" has no imagination.


  6. #6

    Default Re: bk12 bearing eplacement

    Matched ac bearings can directly be jammed together and will give the right preload. If not matched you need a shim between eg the outer rings, and the thickness determines the preload, unless you just adjust the locknut to the right preload.
    I hope this made sense, but angular bearings only takes axial load in 1 direction, and that is why you use 2 eg. back to back, and preload them for no backlash with a locknut.
    This was the short story, the long one can be found via google, and I have put many hours into this, and still not very wise....

    edit : the thickness of the washer needed for normal preload is pretty thin, aprox 2-4um, plus the slack in the bearings..(0.003mm maybee:-)
    The moral of the story is, that you can buy a mached set for your bk12 for 10usd in china, buy the b suffix as it is 40degrees and put them in and tighten the nut, voila. Only masochists like me buy them single as I go the hard way :-)
    This advice is for making a cheap bk12 work, other people use 10-100 times this amount for their more professional machines and want grades as abec 7 or 9 from skf or other quality brands, far better than what we can afford or need.

    Last edited by Mikeedd; 09-27-2020 at 05:50 PM.


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    Default Re: bk12 bearing eplacement

    Hey everyone, thanks for the responses, I'm glad it's not just me having the learning curve!

    I emailed around 10 companies. A few said these bearing were too specialised- dead end. A few quoted mega expensive replacements (a brand labelled FAG, which was quoted at £50 a bearing!!)- dead end. A few kept asking for more and more spec, one of which being what kind of pre load would i like- heavy, medium or light duty. I could google most of the spec, but I couldn't figure out what the hell pre load means. If anyone can direct me to a website that explains this I'd be grateful.

    2 companies gave me a choice between the cheap chinese replacements and an expensive higher quality alternative. The company i went for in the end if anyone would like to know is called simplybearing.co.uk. I couldn't find the bearing on their online shop, but they responded really quickly via email with the bearings i needed and also suggested i buy some Truloc Superfit 211 too along with some installation advice.

    They cost twice as much as buying from a chinese supplier in ebay, but i should get the new bearings in a few days rather than 3 weeks, which is a bigger deal for me than saving £10. I thought i had the installation of the new bearings understood but I haven't come across needing a washer to set the preload. There is no washer in the current BK12's that I've disassembled, just the 2 bearings with the open faces facing each other. Is this washer a major thing for me to understand and include with the replacement process?



  8. #8

    Default Re: bk12 bearing eplacement

    Dear Nic, you only need washer if you do not buy a mached pair



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    Default Re: bk12 bearing eplacement

    Mate. Buy the cheap ones. Screw them into your block correctly. Check there is no backlash. All good. Its a diy cnc router yes and your not machining gear box housings or anything that needs perfect tolerance? I've been using Chinese gear for years.

    Sent from my SM-N970F using Tapatalk



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