$fn = 80;

// Hexagon
module hex(size, height)
for (i = [0, 120, 240])
rotate([0, 0, i])
cube([size, sqrt(3)*size, height], center=true);

rotate([30, 0, 0]) {
    // Barrel
    hex(2, 15);

    // Tip
    translate([0, 0, 5]) 
    intersection() {
        cylinder(h=8, r1=3, r2=0);
        hex(2, 20);
    }

    // Ferrule
    translate([0, 0, -10])
    union() {
        cylinder(h=4, r=2);

        // Ferrule ribs
        for (i = [1, 2, 3])
        translate([0, 0, i])
        rotate_extrude()
        translate([1.6, 0, 0])
        circle(r=0.5);

        // Ferrule rounded ends
        for (i = [0, 4])
        translate([0, 0, i])
        rotate_extrude()
        translate([1.5, 0, 0])
        circle(r=0.5);
    }

    // Eraser
    translate([0, 0, -14])
    intersection() {
        translate([0, 0, 2.7]) sphere(3);
        translate([0, 0, ]) cylinder(h=4, r=1.9);
    }
}