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Re-tapping the end of C-beams

Discussion in 'General Talk' started by Allistar, Mar 4, 2021.

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  1. Allistar

    Allistar New
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    I purchased a kit from the Maker Store in Australia (because it's much cheaper to buy and ship to me in New Zealand). The kit was well laid out and well packaged. This is for the Lead 1515 with the high Z mod. The issue I have discovered during the build is the tapped holes at one end of the 500mm C-beam (for the Z axis) are sloppy. The 20mm screws slide in without "biting" into the thread. I see two solutions:

    1) re-tap the holes with a larger thread. Say 6mm instead of 5mm. Then I find 6mm screws to use.
    2) re-tap the holes to 5mm but go much deeper, and use longer screws so they bite into the newly tapped part.

    Questions:
    Can you re tap at 6mm over a 5mm tap?
    Are there any other solutions?
    What do you recommend I do? (I could wait for a replacement but that'll take about 10 days and I excited to get this built.

    Thanks,
    Allistar.
     
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    I would go for the deeper option :) should be quite easy.
     
  3. Rob Taylor

    Rob Taylor Master
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    M6 tap drill is 5.0mm. Screws are usually a hair undersize for clearance. Sure it's not already tapped to M6 if the screw slides in?
     
  4. Allistar

    Allistar New
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    An M6 screw won't fit. The ends of the holes on this end of the c-beam seem a bit flared out, as if someone was a bit sloppy tapping the holes.

    I've tried retapping at 5mm but the longest tap I can get is about 20mm which is too short. I'll drill the holes out to 5mm and tap to 6mm. Just as well there are two holes at the end of the c-beam that don't get used so I can use those to experiment with. Thanks for your help.
     
  5. Pele

    Pele New
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    What about using a helicoil? Although you might end up drilling and re-tapping to M6 to put one in, but is its that sloppy you might be able to put one in without.
     
  6. Allistar

    Allistar New
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    Thanks for the idea. I'll see how I go retapping it first.
    I had considered the crazy idea of getting long rivets and "expanding" them into the hole and basically rivetting the endplate on. I'm confident that it would hold very well especially as there is an internal thread, but then I wouldn't be able to easily get the end plate off.
     
  7. Pele

    Pele New
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    If you were going to try that, you could maybe try a rivnut, but they are normally used on plate metal or box section.
     
  8. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Have you considered contacting the supplier for a replacement? You shouldn’t have to accept a patch job over their sloppiness.
     
  9. Allistar

    Allistar New
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    I have contacted them and am waiting for a reply. I'd rather not wait the 10 or so days it'll take to send me a new c-beam. If the fix is easy then I'll just do the fix.
     

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