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Repair Ideas for mill ways?

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  • Boostinjdm
    replied
    Originally posted by old mart View Post
    What did you do to get the leadscrew and nut back in line?
    I don't remember needing to do anything.

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  • old mart
    replied
    What did you do to get the leadscrew and nut back in line?

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  • Boostinjdm
    replied
    Yes TJS, I wanted a nice flat surface that would require minimal shimming when I set up to machine the critical parts. The bottom of the knee was raw casting and anything but flat.

    I don't know how do explain it any better than that.

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  • vpt
    replied
    Getting some nice surface finishes!

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  • tjs
    replied
    Originally posted by Boostinjdm View Post
    Ok. On my phone. So I'll give you the short version.

    I set the knee upside down on my other mill. Shimmed it till the z axis ways were perpendicular to the table. I built up the bottom of the knee with epoxy and then machined it all flat. That gave me a good surface that should be parallel to the y axis ways.

    Flip the knee right side up. Get the z axis dialed in again and clamp it down.

    After that I took light cuts on the original y axis ways.






    The underside of the saddle was much easier, but had it's own challenges. I had to grind a custom cutter to reach back into the corner while fly cutting.
    Thanks. I guess I do not understand. So you are actually machining the epoxy ?

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  • Boostinjdm
    replied
    Ok. On my phone. So I'll give you the short version.

    I set the knee upside down on my other mill. Shimmed it till the z axis ways were perpendicular to the table. I built up the bottom of the knee with epoxy and then machined it all flat. That gave me a good surface that should be parallel to the y axis ways.

    Flip the knee right side up. Get the z axis dialed in again and clamp it down.

    After that I took light cuts on the original y axis ways.






    The underside of the saddle was much easier, but had it's own challenges. I had to grind a custom cutter to reach back into the corner while fly cutting.

    Leave a comment:


  • tjs
    replied
    Originally posted by Boostinjdm View Post
    Looks like I've failed to keep this thread up to date. All damaged surfaces were machined. This mill has been back together for a few years now, but not put into service as I've been waiting to install way covers and a DRO. Well, DRO showed up yesterday. So I'm back at it.

    I can go into more detail on the way repairs if anybody is curious how I did it.
    I see you on WW. What did you machine to ways with. My ways on my Y axis get real tight when getting close to their limits. I have forearms to prove it.

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  • Ringo
    replied
    I think a lot of people would be interested in your ways repair.
    A lot of us cannot buy new or recent machines, a lot of us believe there is inherent accuracy in the sheer mass of the old machines.

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  • Boostinjdm
    replied
    Looks like I've failed to keep this thread up to date. All damaged surfaces were machined. This mill has been back together for a few years now, but not put into service as I've been waiting to install way covers and a DRO. Well, DRO showed up yesterday. So I'm back at it.

    I can go into more detail on the way repairs if anybody is curious how I did it.

    Leave a comment:


  • Boostinjdm
    replied
    I was thinking about it. I might have a go at it if I can find a test piece to practice on.

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  • vpt
    replied
    Are you going to flake the surfaces?

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  • Boostinjdm
    replied
    Saddle done. Took off .013".

    Any thoughts on adding Z grooves for oil?

    Last edited by Boostinjdm; 04-26-2015, 03:41 AM.

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  • Rustybolt
    replied
    Yes. That looks bad. If you insist on some kind of repair. Do as others have suggested and add rather than machine off. Once you've removed material it is difficult to put it back. I would hazard that machining .100 off the surface will have a considerable impact on how the machine functions.

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  • jhe.1973
    replied
    Originally posted by Boostinjdm View Post
    Saddle appears worse than the knee. Most of the gouges in the knee are less than .005" deep according to my depth mic.

    The saddle has visible machining marks on the ways. They were not ground, scraped, or even flaked. So despite objections here, I'm not ruling out milling the damaged surfaces.
    I am glad that you are aware of the limitations of a knee mill. My post is not as much of an objection to what you are considering as it was to mention something I didn't know if you knew.

    I hope to never put a damper on a person trying something that may be new to them, just hope to help provide another perspective.

    That being said, the work that your saddle needs brings up another problem.

    If the top and bottom locating surfaces of the saddle are not extremely parallel to each other, the table will not sit square in relation to the column.

    This will become a nightmare if the machine is used for any accuracy. If a feature of a part is located and the knee moved up or down, the feature will seem to move in relation to the spindle and the column will appear to be out of square.

    When I first started in a machine shop decades ago, our M series B-port had a saddle that had not been accurately rebuilt. We couldn't ever move the knee once a part was located & w/only 3 inches of quill travel, it made setups a PITA.

    As long as you are aware of this need for accuracy and take appropriate steps, you can repair the wear surfaces of the saddle with good results.

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  • Boostinjdm
    replied
    Dry fitting shows about a 1/4" wide strip of smooth saddle way contacting smooth knee way. Also, other than the lead screw nut, there is plenty of room for the saddle to drop and move to the left. Which is what would happen if I remove about .005" from both the saddle and the knee. I could actually remove almost .100" each before running into problems. That means I could screw it up several times and still be able to fix it without build up.

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