3D-printed caps for protruding bolts

When I attached our children’s swing to the ground there was still a significant piece of sharp-ish threaded metal sticking out above the bolt head and I was worried about them falling on it. Grinding the end off might still leave some sharp parts, so I thought it safer to print plastic covers for them.

I designed the caps using OpenSCAD, using the ScrewsMetric library for the bolt-shaped inset.

You can see the source code for the design in this GitHub gist:

include <ScrewsMetric/ScrewsMetric.scad>;

$fn = 30;
GHOST = false;
outer_size = 40;

difference() {
    sphere(d = outer_size);
    translate([-outer_size/2,-outer_size/2,0]) cube(outer_size);
    translate([-outer_size/2,11,-outer_size+1]) cube(outer_size); // cut
    rotate([0,0,30]) translate([0,0,0.002]) BoltNormalWithSurface(hexHeadBolt, M12, 15+0.002);
}

The biggest challenge was to find an acceptable compromise in shape and size:
– tall enough to cover the top of the bolt
– narrow enough base to fit next to the swing’s leg
– should be printable without overhangs and no need for supports

The final design I went with is a bit different from in the photo above because that one didn’t fit. I kept the size the same and chopped off one side of the dome to leave space for the swing’s leg.

You can download the generated STL files for printing from the Thingiverse website.

It printed really well and I stuck the pieces in place with some leftover silicone.