CNC Half Nuts: The Smell of Melting Plastic…

After cutting down the Y axis screw for the CNC gantry router project we had a short piece of 3/4 inch Acme leadscrew remaining that was just long enough to drive the Z-axis.  Buying an ACME tap to make a single nut was out of the question as they are normally over $100.  So we set about heat forming a threaded nut from some bits of scrap UHMWPE (Ultra High Molecular Weight Poly Ethylene).  We made the nut in two halves with the intention of  shimming them in the final build, this will allow for slight adjustment while keeping backlash under control.  According to Wikipedia, UHMWPE has a melting point of around 145°C and a co-efficient of friction that approaches Teflon.  Up next is short video of the thread forming followed by some drive testing with the cordless drill.

5 Responses to “CNC Half Nuts: The Smell of Melting Plastic…

  • Great video here. Thanks for sharing.

  • That’s super cool. I think this will work. If you look at my post on Mambohead, guy commented with a video on making a tap out of a piece of acme threaded rod.

  • We considered making a tap from the end of the ACME screw as a secondary option. But in the end, the first try of the melt formed nut was good enough for our purposes.

  • Why build you own on this item? You can buy a 3/4″ ACME bronze or plastic nut for ~$35 at most supply houses. They have external threads for attaching their flanges or you can roll your own [carrier/flange/mounting plate] from that point.

  • Because we can…

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