bare-high/gpt-5.6-sol / tier-3-butt-hinge

```openscad
$fn = 96;

leaf_length       = 30;
leaf_width        = 25;
leaf_thickness    = 2;

knuckle_length    = 6;
knuckle_outer_d   = 8;
knuckle_inner_d   = 4.6;
knuckle_radius    = knuckle_outer_d / 2;

pin_diameter      = 4;
pin_length        = 32;

leaf_clearance    = 0.2;
web_overlap       = 0.1;

through_hole_d    = 3.2;
countersink_d     = 6;
countersink_depth = 1;

hole_y_positions  = [7, 15, 23];
hole_x_offset     = knuckle_radius + leaf_clearance + 18;

eps = 0.02;

module y_cylinder(d, h, y0 = 0) {
    translate([0, y0, 0])
        rotate([-90, 0, 0])
            cylinder(d = d, h = h);
}

module countersunk_hole(x, y) {
    translate([x, y, -leaf_thickness / 2 - eps])
        cylinder(
            d = through_hole_d,
            h = leaf_thickness + 2 * eps
        );

    translate([x, y, leaf_thickness / 2 - countersink_depth])
        cylinder(
            h  = countersink_depth + eps,
            d1 = through_hole_d,
            d2 = countersink_d
        );
}

module leaf(side = 1, segments = []) {
    inner_edge = knuckle_radius + leaf_clearance;
    plate_x = side < 0
        ? -(inner_edge + leaf_width)
        : inner_edge;

    web_inner = knuckle_inner_d / 2 - web_overlap;
    web_outer = inner_edge + web_overlap;

    difference() {
        union() {
            translate([plate_x, 0, -leaf_thickness / 2])
                cube([leaf_width, leaf_length, leaf_thickness]);

            for (segment = segments) {
                y0 = segment * knuckle_length;

                y_cylinder(
                    d  = knuckle_outer_d,
                    h  = knuckle_length,
                    y0 = y0
                );

                if (side < 0) {
                    translate([
                        -web_outer,
                        y0,
                        -leaf_thickness / 2
                    ])
                        cube([
                            web_outer - web_inner,
                            knuckle_length,
                            leaf_thickness
                        ]);
                } else {
                    translate([
                        web_inner,
                        y0,
                        -leaf_thickness / 2
                    ])
                        cube([
                            web_outer - web_inner,
                            knuckle_length,
                            leaf_thickness
                        ]);
                }
            }
        }

        for (segment = segments) {
            y_cylinder(
                d  = knuckle_inner_d,
                h  = knuckle_length + 2 * eps,
                y0 = segment * knuckle_length - eps
            );
        }

        for (hole_y = hole_y_positions) {
            countersunk_hole(
                side * hole_x_offset,
                hole_y
            );
        }
    }
}

module left_leaf() {
    leaf(side = -1, segments = [0, 2, 4]);
}

module right_leaf() {
    leaf(side = 1, segments = [1, 3]);
}

module hinge_pin() {
    y_cylinder(
        d  = pin_diameter,
        h  = pin_length,
        y0 = -1
    );
}

color([0.68, 0.72, 0.76])
    left_leaf();

color([0.78, 0.81, 0.84])
    right_leaf();

color([0.35, 0.38, 0.42])
    hinge_pin();
```