Uploaded a version with a bigger hole around Z motor shaft, so now it is completely usable for those people willing to use plum couplers. Still has the gap on the inner side, so it's pretty easy to reach the couplers' setscrews with an allen wrench.
Regarding the X motor piece, now it is 2mm wider, and has a slightly shorter stroke, since there's no need of 20+mm stroke for such a precise thing. Additionaly, I moved the holes upwards, because with 3mm glass sheet mine was almost at the end of its stroke. Also moved the vertical hole 3mm closer to X motor front plate, so now it lines up almost perfect with the endstop wheel. Still, I recommmend using a nylock nut at the bottom end of the bolt in order to increase contact area without printing too small parts.
I will upload pictures as soon as I have assembled the new version of both pieces.
This is a remix of Meermeneer Z Endstop Fine Adjustment for Anet A8. I made it more rigid, so now the motor piece should be bolted to all four holes of the stepper motor. Besides, I made the top part a bit bigger, so it has some more travel, just enough to have a 3mm borosilicate glass plate on the heated bed.
I recommend using a M3x20mm allen bolt for the fine adjustment. You'll need M3x18 for the stepper.
You might have to drill a little bit for the fine adjustment bolt hole. In that case, grab a pair of pliers, and just twist a 2.5mm diameter drill bit to remove some more microns. Then just use some mineral oil and fasten the bolt with the allen wrench.
It could be changed a little bit to fit 1/8" bolts in case you live in the US, just let me know via comment.
There are some minor changes between the version installed in my printer and the one available here, mostly reinforced corners and some chamfers,