I made a laser alignment tool for validating the alignment of my homemade bike frame jig.It mounts on the bottombracket post and checks that the headtube/seattube cones are in plane.
I wanted it to be accurate to within 1mm at 1m from the BB for future cargobike builds. This meant that the laser needed to be within 0.06 degree perpendicularity of the BB shell. I was scratching my head thinking about precision machining (i’m just a hobbyist and can’t hold tolerances like that).
I ended up 3d printing the thing adding a bunch of adjustments using bolts and using the milling machine bed as a surface for aligning it. I fired the laser at the opposite wall and adjusted until it was within spec.
I’m really happy with this, I honestly didn’t think it would work.