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Thread: Vacuum Chuck Adapter

  1. #16
    Join Date
    Feb 2008
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    E TN, near Knoxville
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    6,036
    Quote Originally Posted by Brice Rogers View Post
    I think that I also need to buy a higher volume pump. I did a science experiment this afternoon and measured it's CFM. My current pump is a little low on volume and that is exacerbating the leakage problem.
    I've never measured the CFM on mine but I can see how that would help with a leaky system. It's bad enough with porous wood and imperfect seals to the wood!

    Too bad we don't live closer or I could loan my vacuum pumps for comparison. I bought a new one from Joe Woodworker and a used one from a woodturner.

    JKJ

  2. #17
    Join Date
    Apr 2018
    Location
    Cambridge Vermont
    Posts
    156
    Brice, Since you machined that piece of aluminum why not add the ability to install a lip seal?

  3. #18
    Join Date
    Sep 2015
    Location
    San Diego, Ca
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    989
    I learned something surprising that I will share.

    There are two types of "sealed" bearings. One is called the "non-contact" seal and the other is a contact seal. I'm guessing that the non-contact seal is more common. I was told this by my bearing supplier (VXB) that they supply non-contact seals. What this means is there is an air gap between the rubber and the inner race. In my case there was a roughly 0.007 " gap. I shake my head in disbelief! I don't understand why they don't just call it a shielded bearing. But perhaps in a shielded bearing, the gap is even wider. Perhaps the standard non-contact "sealed" bearing has a smaller gap.

    When I do a google search, I find some mfrs that offer a contact type of sealed bearing and some the non-contact type. But when I look at sites like ebay, Amazon or McMaster-carr, I don't see that they provide the detail to figure which you are buying.

    Alex, you mentioned a lip seal. Is that a seal that I could buy and attach or is this a seal that I would need to machine myself? I'm familiar with automotive lip seals on wheel bearings, but am unaware of their use on smaller shafts (mine is about 10 mm). Could you provide more info?
    Last edited by Brice Rogers; 06-13-2018 at 1:01 AM.

  4. #19
    Join Date
    Apr 2018
    Location
    Cambridge Vermont
    Posts
    156
    It's a seal you can buy. Sealed bearings are designed to keep things like water out of them, not to hold a vacuum. Since you aren't looking for perfect I'm sure an oil seal would work. They are cheap and easy to get. They come in the same size as the bearings, just thinner, and will press into the aluminum housing and the 'lip' will seal against the shaft. You'll have to modify your design some. You'll want the spring inside the seal to be on the non-vacuum side and if at all possible you will want the seal between the vacuum and the bearing. Grease doesn't like being pumped down in a vacuum (they do make special grease that does). If you put the bearings under vacuum you will most likely pull some of the grease out of the bearing and onto your work. I'm assuming that if you machined the aluminum housing then it shouldn't be too much harder for you to make room for a seal.
    scvi.jpg

  5. #20
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    Sep 2015
    Location
    San Diego, Ca
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    Thanks for posting, Alex. You have helped to expand my knowledge base.

    If I could find the right diameter seal, I could place it on the shaft connecting the two "sealed" bearings. I've also thought if just machining a tight tolerance steel or aluminum seal with minimal clearance (like 0.001) and place it between the two sealed bearings.

    There are a lot of do-it-yourself designs on the internet that don't rely on a seal. Perhaps those folks stumbled onto a contact-type sealed bearing. I ran across on mfr. that mentioned a bearing that was triple sealed (I suspect that it is the contact type). I'm wondering what companies like Harrison Specialties, and frugalvacuumchuck do? I wonder if they add a seal in addition to the double shielded (contact-style) bearing ? When I read the description from JT Turning, it could be interpreted that there is some sort of proprietary seal in there. hmmm.... food for thought.

    Thanks again for pointing me in the direction of shaft seals.

  6. #21
    Join Date
    May 2003
    Location
    NW Arkansas
    Posts
    177
    A couple pics of my vacuum adapter I made a few years ago. I use it a lot and haven't had any problems. Can't remember what bearings I used or where I got the seal from but you can get the general idea from the pics.

    DSCF9010.JPG

    DSCF9008.JPG
    Larry

  7. #22
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    Feb 2008
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    E TN, near Knoxville
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    Quote Originally Posted by Larry Copas View Post
    A couple pics of my vacuum adapter I made a few years ago.
    Very nice work Larry!

    JKJ

  8. #23
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    Sep 2015
    Location
    San Diego, Ca
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    989
    Thanks for posting, Larry. Looks very nice.

  9. #24
    Join Date
    Sep 2015
    Location
    San Diego, Ca
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    Larry, I have a supply of the 6200-2RS (non-contact) bearings (that leak - - as I reported previously). They are 30mm OD and 10 mm ID. I found a source for a grease and oil seal. I'm wondering if you could look at the specs below and comment as to whether this seal is likely to work or whether I'm looking at the wrong type of seal:

    Oil and Grease Seal Double Lip Shaft Dia. 10mm Width 7mm For Bore Dia. 30mm Nitrile Rubber Lip Material.
    Brand : VXB
    Item Sku : TC10x30x7
    Type : Oil and Grease Seal TC 10x30x7 mm
    Inner : 10mm
    Outer : 30mm
    Width : 7mm
    Size : 10mm x 30mm x 7mm
    Oil and Grease Seal Material : Nitrile Butadiene Rubber
    Temperature Range : -40 to 248F

    TC10x30x7-2 seal.jpg

  10. #25
    Join Date
    May 2003
    Location
    NW Arkansas
    Posts
    177
    Looks similar to the one I used but smaller. My seal measured 18 x 40 X 9. I really can't comment on if it will work as I'm one of those shade tree machinists and not that knowledgeable.
    Larry

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