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  • #61
    I have a Deckel FP1 mill
    with split nuts,
    but the nuts are 2" long each !
    Probably 50mm but whatever.
    They were designed to have 2
    separate individual nuts and
    designed to be a backlash takeup
    design.
    People have been known to cut
    a Bridgeport table nut in half to
    achieve backlash takup, and that
    works, but then it wears out rather
    quickly.
    I have also seen the side securing
    slotted screw on a Bridgeport allow
    the nuts to start to float in their iron
    housing. I know that is what Jerry
    is talking about, loose in the mounting.
    But creating a split nut without making
    another to give more length, you might
    not be happy in the long run.
    One stopgap thing I did on a feed nut
    for the top slide on one of my lathes...
    The bronze nut was worn, but not too
    bad. It had maybe a quarter turn of lash.
    So what I did, was put it in the press and
    squash it flatter. Not change the pitch
    by squashing it axially, that would work
    too, but take away thread area. I squashed
    it along its whole flat length. I basically
    made the through hole of the threads
    an squashed oval rather than a circle or
    cylinder. This made the threads of the
    Acme mesh deeper with the nut. Yes it
    did take away contact on the sides of the
    nut, for sure. But it bought me time to get
    around to making another nut. I was more
    experimenting to see if it would work.
    I got the idea when I saw someone squashed
    a 1/4-20 hex nut to make it fit a #14-20 bolt.
    Yes the nut hex was squashed, but the
    bolt was tight and no wiggle. I did the same
    thing to my lathe feed nut.

    -D
    Last edited by Doozer; 03-02-2022, 03:11 PM.
    DZER

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    • #62
      Crushing the nut oval like that would be similar to that pinch style that OM found. As you say, not ideal by a long shot. But buys a little time provided we don't get distracted and forget about how much time it did buy....

      But just to prod at the beast....... If you don't mind backlash because it's just a fact of life then why squish the nut in the first place?
      Chilliwack BC, Canada

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      • #63
        The "ovalizing the nut" trick is similar to what is done on some dividing heads. In those, the depth of mesh is adjustable, so that the worm screw can wear deeper into the spindle worm gear.

        Squashing it oval is a little cruder, and not very adjustable, but would do about the same thing in the end.

        So would splitting the nut...... if done longways, and not crosswise. Similar idea to Post 45 link, but a full cut through.

        That split could be made spring-loaded, so that the wear would still occur, but would be continuously adjusted for, and would occur on a large area, so would be slower.

        The two halves could be made to float perpendicular to the scerw, so they would not wear off to one side like the Post 45 idea.

        Originally posted by BCRider View Post
        No, no.... Doozer has a point.....................
        Of course Doozer has a point.

        Too bad the "point" has nothing to do with the post he complained about, which referred to adjusting the thrust bearings, and making sure the nut was solidly attached to the table, and not sliding around because the screws are loose.......

        About the "point"..... I'd venture to say that just about all of the ways you can split a feed nut will increase wear if tightened. If you make the two sides as long as the whole original nut, you do lose a little travel, and the wear is still twice as much as if you used that whole nut as one solid piece, even though it is better than splitting the original nut.

        There is a reason some makers of good mills allowed the special anti-backlash adjustment to be easily activated for climb milling, and de-activated when not required.

        Of course, if you have a backlash problem, you may have to add drag to the table to avoid it slamming and bouncing through the backlash. Typically that is by by slightly snugging the table lock. That adds wear also. So there is extra wear in several of the ways of dealing with backlash, at least the kind that is due to the nut being worn, and not just being loosely attached..

        Last edited by J Tiers; 03-02-2022, 06:13 PM.
        CNC machines only go through the motions

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        • #64
          Another real advantage of having minimum backlash on a mill is being able to position things in all directions with reduced repositioning of the dials. Not all of us have or can afford DRO's. I have been drilling multiple holes in a plate today using drawing dimensions and the new nuts that I made for the drill mill have made it easier. Next step will be new redesigned scales and proper adjustable thrust bearings for the leadscrews. See post #16.

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          • #65
            I would start to sell my blood every week
            if I could not afford a DRO for my mill.
            That is how much I believe they are
            necessary. If you are using your mill
            for slabbing or straight metal removal,
            like some use horizontal mills for, then
            a DRO is not necessary. But if you are
            machining features on a part, dicking
            with dials is a recipe for disaster.
            Call me a fool, call out my man-gina.
            But pry my DRO from my cold dead
            fingers. I feel that strongly about it.

            --Doozer
            DZER

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            • #66
              I don't own a mill, Doozer, the drill mill and the Tom Senior belong to the museum I am a volunteer at, buying tooling bit by bit for the machine shop for the last 14 years. DRO's and power feeds would be nice to have, but small pension and huge fuel increases make them just wishful thinking.

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              • #67
                Originally posted by Doozer View Post
                I would start to sell my blood every week
                if I could not afford a DRO for my mill.
                That is how much I believe they are
                necessary. If you are using your mill
                for slabbing or straight metal removal,
                like some use horizontal mills for, then
                a DRO is not necessary. But if you are
                machining features on a part, dicking
                with dials is a recipe for disaster.
                Call me a fool, call out my man-gina.
                But pry my DRO from my cold dead
                fingers. I feel that strongly about it.

                --Doozer
                Gotta agree.... I do NOT have a DRO on the Benchmaster, and it's a pain. Do-able, but a pain.

                The cheap DROs are not very accurate if you look at the specs (unless they changed a lot recently). The mill is really not worth a better DRO.

                I suppose you could argue that the accuracy of the cheap DROs is better than losing count of a whole turn of the dial, and you'd be correct on that for sure. Good argument for putting one on it.
                CNC machines only go through the motions

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                • #68
                  Part 2: https://bbs.homeshopmachinist.net/fo...duction-part-2

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