Latest (easiest) iteration for a Stepper_motor-to-squareTubing_Mount.
Back bracket could be replaced with hose steel clamp although I suspect lateral wiggle at rotation change will happen and that could be an issue. One more possible issue: making sure the top holes and bottom holes are at the same distance fromo one another to keep the motor parallel with the square tubing.
You could all most 3d print the bracket…
I will buy this angle for some more parts of the printer and you’d have to buy at least 1m of it so if it’s already there I’d better use it all. Good use of materials :).
This one looks pretty simple and effective. Could probably miter-cut the ends a bit and chamfer off the outside corners to make it look super clean.
@Ryan_Carlyle
For whoever has the tools yes. I am thinking about how to do this printer best on the kitchen table with as little tools as possible. Many of my friends abroad, where I used to live for some years, live in small apartments, many in studios and barely have an electric drill for home repairs (and the usual hammer, screwdrivers, ruler & that kind of stuff) …
@Florian_Ford Sure, fair enough. Not hard to do with a hacksaw / file / dremel but it IS hard to do cleanly that way 
I am thinking going even shorter, so the bracket only catches the upper mounting holes:
https://photos.google.com/share/AF1QipOMFEcqxDzCp1UDJ76U8xeg5FW7cjtE_oeu567HNY7ATX9llTcl76WY8RcLtNglfQ?key=MF9EeE9HY1RRSVFqdWhiY2hoQVJFMFJOa1FOcl9n <<
The holes positions can also be quite accurate by drilling both front brackets at the same time and then using them as templates for the other pair.
@Nathan_Walkner I only need it up and down for this particular application. You can see better on the thingiverse project page:
SCOUTcorexy 3D Printer (square aluminum tube frame, scout-tower-like corner nodes, dual-support Z, lots of adjustability to compensate for construction errors) by florinf-ro - Thingiverse <<<
This is the model with all plastic parts that I am trying to achieve. I am replacing some plastic parts with sturdier but easy to make aluminum angle parts and will upload that to sketchfab at least. Until then the all-plastic parts model can be navigated in 3D here: >>> SCOUTcorexy:V3:hXYZ∅10:LM10UU:F694ZZ:GT2 - Download Free 3D model by thorfab [c66972e] - Sketchfab <<<
The only grief I have with this repstrap (let’s call it like that) solution is that it’s not adjustable like the other clamps are, this one needs pretty exact distanced holes so that the motor touches the tube above it for maximum Z and minimal chances to rock, so the up-most holes and the motor mounting holes should be in such a way drilled that there is no gap between the motor and the tube above it. Although that can somehow be rep-strapped itself if not perfectly nailed by adding shims below the bolts that rest on the tube…