Instructables
Picture of Flexible CNC leadscrew nut

This is my first 'structible so I decided to do something very simple yet helpful to the right people. I followed several very good Instructables on making your own CNC machine however, I ran into some trouble moving my tables using NEMA-17 stepper motors. These motors don't have a lot of torque and due to the difficulty of getting the leadscrew nut perfectly straight I ran into some issues with the leadscrew being difficult to turn. My solution was to create a mount for the leadscrew nut that could flex and conform to the path of least resistance on the leadscrew. The final product is a piece of rubber hose with a threaded sleeve pressed into it and mounted to my tables by two metal bars that clamp the hose in place when tightened down.

 
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Step 1: The original leadscrew nut

Picture of The original leadscrew nut

This is the original leadscrew nut mount. This made the tables very difficult to move because of the bind it put on the threads inside the nut due to its misalignment. I tried on several occasions to get the alignment just right however, nothing I did resulted in making it easier to turn the leadscrew.

Step 2: Hose

Picture of Hose

I used 4 inches of rubber hose with on ID of 3/8 in. Your application will most likely be different as I used 5/16 - 18 thread for my leadscrew for my CNC machine. Just make sure the ID is at least 1/16 in larger than the diameter of your leadscrew.

Step 3: Leadscrew nut

Picture of Leadscrew nut
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I bought a coupling nut and cut it round using a lathe. I got lucky as once the nut was round, it fit snugly into the hose. It is not necessary to cut the nut round, just as long as you can press the nut into the piece of hose.

pfred23 months ago

Have you thought about making plastic lead nuts? You can get some Delrin, Nylon, or HDPE and make nuts out of it. Plastic being elastic the nuts are zero backlash.

xXLGXx3 months ago

I assume that this did solve your binding issue? Completely or partially?

getoffmylawn08 (author)  xXLGXx3 months ago

Sorry, should have made a results section. But yes this did solve the problem of the tables being difficult to move. I had to use a wrench on the nuts on the end of my leadscrew to make the tables move using the original nut. Using this setup I am able to turn the leadscrew easily by hand. I did forget to mention I put a small coat of light oil on the leadscrew, which also seemed to make it easier to turn.