Replacement knob for gas cooker

gas_knob.scad

height = 7;
d_outside = 17.2;
hole_size = 3.4;
hole_taper = 6;
thickness = 3;

inner = 6;
inner_key = 4.4;

bump_r = 3;
bump_n = 18;

slop = 0.4;

difference() {
    union() {
        cylinder(h=height, r=d_outside/2, $fa=1, $fs=0.5);
        
        for(i = [0 : bump_n]) {
            rotate([0, 0, i * 360 / bump_n]) {
                translate([0, d_outside/2, height/2]) {
                    cylinder(h=height, r=bump_r/2, center=true, $fa=1, $fs=0.5);
                }
            }
        }
    }
    
    //Center hole
    cylinder(h=height, r=hole_size/2, $fa=1, $fs=0.5);

    //Screw hole + taper
    translate([0, 0, height - (hole_taper - hole_size)/2]) {
        cylinder(h=(hole_taper - hole_size)/2, r1=hole_size/2, r2=(hole_taper)/2, $fa=1, $fs=0.5);
    }
    
    //Keyed cutout
    translate([0, 0, 0]) {
        intersection() {
            cylinder(h=height - thickness, r=inner/2, $fa=1, $fs=0.5);
            translate([0, 0, 0]) {
                cube(size = [inner, inner_key, (height - thickness) * 2], center=true);
            }
        }
    }
}