CNC Mill- Replacing Y axis Linear Bearings - Page 2
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  1. #21
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    I never cared for the plastic plugs. IMO, they don't sit flush or flat enough to do a really good job. I've only done rail replacements on 3 machines, but on each one I filled the holes with Moglice. Grease filled the socket heads so it would not fill them though. Moglice would drill out fairly easily if they ever had to be re-done.

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  3. #22
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    Vacbiker: good idea! Never thought of that.

    DavidScott: It leans much less but still does just a little. With my level on there when i move the table to the side it seems to lean about .0005 per foot where I think before it was more like .0015 to .002 per foot. I still have it all torn apart since I am waiting for the hole plugs to come so have not done too much checking. I also dropped and broke my encoder box in the process and knocked the tip off my Haimer so I am trying to get that all fixed. I think I will start the memory upgrade now since the machine is down anyway. That sounds like a project of its own.

  4. #23
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    Quote Originally Posted by Vancbiker View Post
    I never cared for the plastic plugs. IMO, they don't sit flush or flat enough to do a really good job. I've only done rail replacements on 3 machines, but on each one I filled the holes with Moglice. Grease filled the socket heads so it would not fill them though. Moglice would drill out fairly easily if they ever had to be re-done.
    I entirely concur. Non of those rail plugs are worth hammering in. They all leave the chamfer of the counter bore exposed, and the wipers wont pick up debris left in that, so the wiper just tumbles that up, and it works into the linear truck. Don't get me started. I've long been of the impression, those rail plugs are planned obsolescence.

    I fill the head of the socket head cap screw, with a scrunched up ball of aluminium foil, straight out of the kitchen. If you were to pretend you were stuffing a muzzel loader, you can pack the socket of the bolt. The epoxy ends up brittle, so a whack with a pin punch shatters it out.

    I've had arguments with customers when doing this. "Are you sure you want to epoxy over the bolts". My answer is always. "Mate, if I ever have to take these bolts out again, you have bigger problems than a bit of magic mud* in the holes".

    I use some thing called Belzona 1111 Super metal. Its claimed you can do bearing journal repairs with it. Poor man's metal HVOF metal spraying. Never tried that, but its tough as a kidney stone. I fill rail plugs with it. When I was a puppy they used to call it "molecular metal". Its partially filled with steel.

    And I'll tell you the trick. A scrap of Perspex, acrylic or polycarbonate. Pass it through a bridgeport so you have one clean straight edge. I piss about and put it via a toolmakers vice, and my surface grinder. An uber accurate 1 axis paint scraper.

    Mentholated Spirits. I think you blokes call that Denatured Alcohol. Its a release agent between perspex and epoxy. Dip your uber spatula in D.A, and you can work the epoxy. With two minutes practice, you can just nicely, over fill the hole. You want to leave a lump, that you can stone down to be dead flush with the top of the rail. Top of the rail is a redundant surface. Nothing to worry about, by hitting it with a stone. To the point, a stone will plug with the epoxy filling it. I often rough it in with some fine wet & dry under the stone. It needs juice, I use Kerosene to keep the stone rinsed / clean.

    Other trick is to use a heat gun. Nothing smarter than some D.I.Y would use for paint stripping. I use the one I carry for heat shrink tubing. When you plaster in the exoxy, just feather it with a bit of heat from about 10" - 12" away. Tiny bit of heat makes it very viscous, so it wet's the counterbore, and any air bubbles you have "pop".

    Regards Phil.

    *Magic Mud is a generic term we use downunder for Moglice or SKC Gleittecknik

  5. #24
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    Thanks Phil. Here is what the Y axis linear bearings looked like when I got the machine. I took them all apart, cleaned them up, and put new seals on them and have used them for almost 2 years now. They cleaned up surprisingly well but just a little sloppy.

    brother-y-axis-bearing.jpg

  6. #25
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    Quote Originally Posted by machtool View Post
    ......I fill the head of the socket head cap screw, with a scrunched up ball of aluminium foil, straight out of the kitchen. If you were to pretend you were stuffing a muzzel loader, you can pack the socket of the bolt........
    I like this idea! Greasing the sockets was a pain. I had to be super careful that I did not get grease on the counterbore in the rail.


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