So these new screws present a few new issues. Their diameter and thread is not familiar to me. I still suspect the coating. Plus the coating is a lubricant of sorts and will complicate the ability to attach a coupler securely.

My plan here is to thread the lead screw to 1/4-20 in the areas where couplers and thrust adjustment nuts will go. This will remove the coating and allow me to use standard fasteners in those areas.

I have acquired a different type of coupler from Ebay. I bought a smaller bore size so I would fit them on both sides.

Attachment 250786

I purchased these for 3 reasons.

I could use the clamping feature of the coupler to tighten the (soon to be internally threaded coupler) on the matching thread of the lead screw. If necessary loctite could be used also.

On the stepper side of the coupler I could use a grub screw along with the clamping feature. A win win in my book.

I could remove the stepper without destroying the coupler.