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  1. #61
    It was a bit of a bodge springing mine, I added a spacer and 2 Belleville washers. Well 6 spacers and 12 washers to do all the bearings and nuts. But the reward was out of all proportion to the effort.

    Click image for larger version. 

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  2. #62
    Quote Originally Posted by Robin Hewitt View Post
    It was a bit of a bodge springing mine, I added a spacer and 2 Belleville washers. Well 6 spacers and 12 washers to do all the bearings and nuts. But the reward was out of all proportion to the effort.

    Click image for larger version. 

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    So, if I'm interpreting that correctly, you have a double ball-nut set-up like my machine?

    I could do something like this although it would mean making a new retaining flange. I have to say that apart from grinding spindles, I'm not a fan of spring-loaded solutions. I'm also not convinced that backlash of 0.01 is much of an issue. My conventional mill has about 0.25 backlash and it's only a problem with heavy climb-milling or slot milling and then it can be overcome by reducing the feed rate and the depth of cut. Mind you the table and slide alone must way 200kg - mass helps, as do well adjusted gibs.

    I meant to have asked what the rest of you mill consists of Robin - got any pics?

  3. #63
    I don't have a recent pic, here's an old one...

    Click image for larger version. 

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  4. #64
    Quote Originally Posted by Robin Hewitt View Post
    I don't have a recent pic, here's an old one...

    Click image for larger version. 

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    Very neat, especially the Z axis. Wouldn't mind seeing some details of this as I'm sure I'm going to have to go down this route eventually.

    What sort of backlash have you achieved on the x and y?

  5. #65
    There's a build log from many years ago, I will try and link it...
    http://www.mycncuk.com/threads/651-W...ht=Warco+Major
    I fitted zero backlash double nuts, big disappointment, so I sprung them and it was like magic.
    The springs mean that I have no backlash up to 1/4 ton but if I ever pass that loading presumably everything will go horribly wrong.
    I do get some sideways slop in the quill if I forget to pack it out with thick, icky grease. Open to suggestions.

  6. #66
    Quote Originally Posted by Robin Hewitt View Post
    There's a build log from many years ago, I will try and link it...
    http://www.mycncuk.com/threads/651-W...ht=Warco+Major
    I fitted zero backlash double nuts, big disappointment, so I sprung them and it was like magic.
    The springs mean that I have no backlash up to 1/4 ton but if I ever pass that loading presumably everything will go horribly wrong.
    I do get some sideways slop in the quill if I forget to pack it out with thick, icky grease. Open to suggestions.
    I might give the belleville washer thing a go. The Fehlmann's vernier adjustment is clever, but I think a grub screw lock would be better as it would allow finer adjustment. Quality manufacturers have a nice trick of fitting a pressed-in brass plug in the adjustment nut before threading it so that you have a formed locking piece that doesn't damage the thread and needs little pressure to lock.

    Regarding your quill slop, there isn't really a satisfactory solution. The fit of a cylinder into a bore is something that requires a degree of precision and careful fitting at the point of manufacture - surface finish is critical. Any fool with a cylindrical grinder and enough patience can make a cylinder to size and parallel to a micron or two, but getting the bore honed for a perfect transition fit is another issue altogether. Most of the Chinese machines fall at this point, although I have to say that Myford's VMC (Taiwanese) had a pretty decent fitting quill - though not to Swiss, German or the best US and GB standards (has to be said though that most of the machine tools produced in the UK were not of a particularly outstanding fit in this respect).

    You could split the casting and put a clamp in place, but this is a pretty crappy solution as you're going to get lots of point contact at the clamp position (the bore will be an oval) and you'll still have the original clearance further up. Alternatively you could get the quill hard-chromed and ground to a nominal size slightly larger than the clearance, but then you have the difficult honing issue mentioned above. Not worth doing either of these, better to start again with a higher-grade machine and transfer your clever CNC additions to it.

    If you've got space there's been some fantastic 1980s CNC machines on eBay recently including a couple of Deckel FP3/4s for about 1500! Fab things with superb ball-screws and servos (probably old brush types though).

  7. #67
    Quote Originally Posted by Agathon View Post
    Very neat, especially the Z axis. Wouldn't mind seeing some details of this as I'm sure I'm going to have to go down this route eventually.

    What sort of backlash have you achieved on the x and y?
    I meant to have complimented you on the really super job you've done on the casings for the drives - very professional.

  8. #68
    Most kind. This is the magic of CNC, it frees you from straight lines and you enter a wonder land of flowing curves. If I only had 2 more axes I could do blobs.

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