bare-think-off/gemini-2.5-flash-lite / tier-2-hex-bolt

```openscad
// M8 Hex Bolt (shank only)

module bolt() {
    // Bolt head
    head_across_flats = 13;
    head_height = 5.3;

    // Shank
    shank_diameter = 8;
    shank_length = 30;

    // Hex head using hull and cylinders
    // The angle of rotation for each face is calculated
    // For a hexagon, 360 degrees / 6 faces = 60 degrees per face
    // We need to rotate by half of that to center the faces on the axes
    hex_radius = head_across_flats / 2;
    difference() {
        union() {
            // Create a cylinder for the top surface of the head
            cylinder(h = head_height, r = hex_radius, $fn = 6);
            // Create the hexagonal sides by rotating and hulling cylinders
            for (i = [0:5]) {
                rotate([0, 0, i * 60 + 30]) { // Rotate to center faces on axes
                    translate([hex_radius, 0, 0]) {
                        cylinder(h = head_height, r = 0.1, $fn = 6); // Tiny cylinder to define the edge
                    }
                }
            }
            // Create the base of the head using a cylinder
            cylinder(h = 0.1, r = hex_radius, $fn = 6); // Thin cylinder for the base
        }
        // Chamfer the top edge of the hex head slightly (optional but realistic)
        // You can adjust this or remove it if not needed.
        // For simplicity, we'll omit chamfering here to strictly follow the prompt.
    }


    // Shank
    translate([0, 0, -shank_length]) {
        cylinder(h = shank_length, d = shank_diameter);
    }
}

bolt();
```