bare/gpt-4.1 / tier-2-hex-bolt

// M8 Hex Bolt (Thread omitted)

// Parameters
head_across_flats = 13;  // Head width across flats (mm)
head_height = 5.3;       // Head height (mm)
shank_diameter = 8;      // Shank diameter (mm)
shank_length = 30;       // Shank length (mm)
hex_sides = 6;

// Calculate hex radius (distance from center to vertex)
head_radius = head_across_flats / (2 * cos(180/hex_sides));

// Hex head (centered at z = head_height/2, bottom at z = 0)
module hex_head() {
    translate([0, 0, head_height/2])
        cylinder(h = head_height, r = head_radius, $fn = hex_sides);
}

// Shank (extends downward from bottom of head, along -Z)
module shank() {
    translate([0, 0, -shank_length])
        cylinder(h = shank_length, r = shank_diameter/2, $fn = 60);
}

// Assemble
hex_head();
shank();