z-axis coupler grub screws

Discussion in 'Build Help' started by metajack, Apr 16, 2016.

  1. metajack

    metajack Member

    Apr 16, 2016
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    So the build documentation says to remove the upper coupler grub screws before putting the couplers on, but it never mentions to put these back.

    These two posts seem to imply that I'm not supposed to put them back:


    So I'm pretty confused. I hadn't noticed after commissioning that I still had these two grub screws left over. I've done a couple of pretty nice prints that way.

    One thing I noticed that seems a bit different is that if I put the grub screws in and tighten them and then manually turn one of the Z screws, both Z screws will turn. I'm pretty sure this wasn't happening before the grub screws were in.

    Are these supposed to be in or not?
  2. Kick2box

    Kick2box Well-Known Member

    Mar 15, 2016
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    The grub screws are put out because the coupler may be set in an angle when using them. The other (bigger) screw is sufficient.
  3. richgain

    richgain Well-Known Member

    Dec 18, 2015
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    Another good reason for not using the upper grub screws is that they will tighten onto, and potentially damage the thread on the leadscrew. The end result of this is that you will no longer be able to remove the lead screw from the nut at the bottom end and will have to take it right up to the top end if you need to remove it.
    I know this from bitter experience. Trust me, take them out and don't put them back - the larger bolt is enough to grip the screw thread tightly without damaging it.
    Ephemeris likes this.
  4. Ephemeris

    Ephemeris Well-Known Member

    Nov 25, 2015
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    I panicked when I read Richgain's experience. Luckily for me, when I checked just now, I see I never reinstalled the upper set screws in the Z couplers. This feels like dumb luck on my part. The instructions really need to be clear that those set screws are to be discarded.

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