NEW ACME lead screw lock nut

So today there was a surprise package waiting for me at home. It had a brand new ACME lead screw, to replace the one I got last week. (Another big thumbs up for Inventables service, sending this out without even having to ask). Anyway this new screw has some threads on the top so you can screw a nylon locknut above the pulley.

What I am wondering is how to get enough torque the tighten this nut. The picture suggested that I put an allen wrench into the set screw and use that to hold the rod in place while I tighten down the nut. (there is no text or video for the new ACME screw style) But the set screw hex socket isn’t deep enough, the wrench just pops out as soon as you put some torque on it. I tried taking one of the set screws out, but then the pulley doesn’t hold onto the screw with enough friction to resist the torque. I tried gripping the bottom of the screw with some pliers (I didn’t try too hard, because I didn’t want to damage the threads). It just takes too much torque to tighten down those locknuts.

At this point I could try a regular nut, I could put two regular nuts, and tighten them against each other (a jam nut?), or I could wait until I am down with building out the electronics, and hope the Z motor has enough torque to tighten the nut. I’m thinking the second option. I assume this is regular M6x1 threads?

Anyone else get this to work with the the provided lock nut?

Hi @ChrisWundram On the one in our office we put the Allen wrench in the back of the screw just enough to hold it steady. Then the other hand turned the wrench.

If it is popping out try the short end.