Yet another low-cost leadscrew coupling

by keegi, published

Yet another low-cost leadscrew coupling by keegi Jun 15, 2011


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Coupling to connect M8 threaded rod leadscrew to 5mm stepper motor shaft.

(It seems Thingiverse lost the list of materials)
List of materials:

  • 1-2cm of flexible tubing e.g. 4x6 or 4x7mm
  • M8 coupling nut
  • M8 nut for contra


  • slide the tubing on 5mm motor shaft
  • thread one nut (or better yet, a coupling nut) onto the top of the tubing so that half of the nut is above the shaft
  • thread another nut onto the threaded rod
  • screw the rod onto the nut on the motor
  • tighten the rod against motor shaft (but not too tight)
  • tighten the nuts against each other

I used coupling nut on the picture for better grip, but it seems to work with regular nut as well.

I don't see a reason why this shouldn't work for 5/16" threaded rod as well.

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That is not a lead screw. That is a threaded rod. O.O

Not a bad coupling for threaded rods, but... just... wow.

That is a threaded rod.


I've used this setup on both 3DP's & CNC routers for the past 10 years, never had a failure. I usualy solder or pin the coupler to the threaded rod depending on the size, insert the tubing, then press fit the nema shaft. A little spit helps... ;)
I've use this on nema24's with a 1/2" thread on my drillpress XY table, & it's worked perfectly.
Tip: Use stainless threaded rod & nuts. It's a few extra bucks, but well worth it. Threaded is slower than ACME due to the higher pitch, but it can mean better micro-stepping on a tightly tuned machine, which equals better layers.
Spinning the rod in a drill & knocking the sharp edge off the threads with medium grit sandpaper will make it run much smoother.
Depending on use, I change out the tubing about once a year when I do maintenance.

Hope that helps :)


can anyone help me to understand the connection between the flexible tubing and the M8 coupling nut?
Thanks! :D

The threads of the nut should cut into the outer layer of the tubing.

Hahah I love it!!! If only I'd seen this before ordering a set of solid couplers, but oh well.

This is so much smaller than the OEM coupler found in Prusa Mendels. I could gain a couple centimeters of x motion at z=10cm. Very cool. :-)

What type of tubing did you use in your coupler? The two I bought just bind up and tear when I try to thread the nut on.

Damn that's good. I looked at it and it looked a bit flimsy, but trying it its really good.

I attached the coupling and the nut to the rod, used pliers to hold the motor shaft, and screwed the two halves together.

This is great! I printed a few different z couplings, but I could never completely get rid of z axis wobble until I tried your solution.

Thanks for sharing!

I used a lock washer to keep the coupling nut and hex nut together so the the threaded rod didnt accidentally get unscrewed.