bare-low/gpt-5.6-luna / tier-3-butt-hinge

```openscad
$fn = 64;

// Dimensions
leaf_len      = 30;
leaf_width    = 25;
leaf_thick    = 2;

pin_d         = 4;
pin_r         = pin_d / 2;
pin_len      = 32;

knuckle_len   = 6;
knuckle_od    = 8;
knuckle_r     = knuckle_od / 2;
knuckle_id    = 4.6;
knuckle_ir    = knuckle_id / 2;

hole_d        = 3.2;
hole_r        = hole_d / 2;
csk_d         = 6;
csk_r         = csk_d / 2;
csk_depth     = 1;

plate_z       = 0;
axis_z        = plate_z + leaf_thick / 2;

// Cylinder along the Y axis
module y_cylinder(r, h, y0, x = 0, z = axis_z) {
    translate([x, y0, z])
        rotate([-90, 0, 0])
            cylinder(r = r, h = h);
}

// Countersunk through-hole along Z
module countersunk_hole(x, y) {
    union() {
        translate([x, y, plate_z - 0.1])
            cylinder(r = hole_r, h = leaf_thick + 0.2);

        translate([x, y, plate_z + leaf_thick - csk_depth])
            cylinder(
                r1 = hole_r,
                r2 = csk_r,
                h = csk_depth + 0.01
            );
    }
}

// Left leaf: x < 0, knuckles at segments 0, 2, 4
module left_leaf() {
    difference() {
        union() {
            // Flat leaf plate
            translate([-leaf_width, 0, plate_z])
                cube([leaf_width, leaf_len, leaf_thick]);

            // Three knuckles
            for (y0 = [0, 12, 24]) {
                y_cylinder(knuckle_r, knuckle_len, y0);
            }
        }

        // Knuckle bores
        for (y0 = [0, 12, 24]) {
            y_cylinder(knuckle_ir, knuckle_len + 0.2, y0 - 0.1);
        }

        // Three M3 countersunk holes
        for (y = [7, 15, 23]) {
            countersunk_hole(-15, y);
        }
    }
}

// Right leaf: x > 0, knuckles at segments 1, 3
module right_leaf() {
    difference() {
        union() {
            // Flat leaf plate
            translate([0, 0, plate_z])
                cube([leaf_width, leaf_len, leaf_thick]);

            // Two knuckles
            for (y0 = [6, 18]) {
                y_cylinder(knuckle_r, knuckle_len, y0);
            }
        }

        // Knuckle bores
        for (y0 = [6, 18]) {
            y_cylinder(knuckle_ir, knuckle_len + 0.2, y0 - 0.1);
        }

        // Three M3 countersunk holes
        for (y = [7, 15, 23]) {
            countersunk_hole(15, y);
        }
    }
}

// Pin axis, extending 1 mm beyond each end of the 30 mm knuckle stack
module hinge_pin() {
    color("silver")
        y_cylinder(pin_r, pin_len, -1);
}

// Assembly
color("dimgray")
    left_leaf();

color("dimgray")
    right_leaf();

hinge_pin();
```