Nut Trap

While working on another issue of joining multiple prints into bigger objects I didn't want to glue things, but join them some other way.

What I wanted to do was print them, with nut's inside the print to secure them.

To that effect I use the M0 command(and others in Marlin) and insert it at the relevant layer so that it pauses the print so I can insert the nut's mid print, and then un-pause it finish the rest of the job.

As such I make this test cube, suited for M4, as well as working out how to manage angled bolts/nut's and how to insert them.

My initial attempt at this I had to much slop in the size of the nut hole, and 2 of the 3 nuts just turned in the prints as I attempted to screw them.

This second attempt all 3 of them screwed in perfectly and tightened up with no problems, both the vertical and 45 degree angle one had not issue.

I also designed as part of this test recessing of the bolt head so it doesn't stick out of the print after its tightened.

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