Simple openscad function/module to create ISO screw threads

openscad_iso_thread

module m5_thread(height=1,quality=4) {
	r_maj = 5/2;
	pitch = 0.8;
	iso_h = sqrt(3)/2*pitch;
	r_min = r_maj - 5/8 * iso_h;

	linear_extrude(height=height,twist=360*height/pitch) hull() for(j=[0,1]) mirror([j,0,0]) for(i=[0:(180/8)/quality:180]) {
		if (i==0) {
			square([0.01,r_maj]);
		} else if (i==180) {
			translate([0,-r_min]) square([0.01,r_min]);
		} else if (i<22.5) {
			translate([min(0,r_maj*sin(i)),min(0,r_maj*cos(i))]) square([max(abs(r_maj*sin(i)),0.01),abs(r_maj*cos(i))]);
		} else if (i>135) {
			translate([min(0,r_min*sin(i)),min(0,r_min*cos(i))]) square([max(abs(r_min*sin(i)),0.01),abs(r_min*cos(i))]);
		} else {
			translate([min(0,(r_min+(1-(i-22.5)/112.5)*(r_maj-r_min))*sin(i)),min(0,(r_min+(1-(i-22.5)/112.5)*(r_maj-r_min))*cos(i))]) square([abs((r_min+(1-(i-22.5)/112.5)*(r_maj-r_min))*sin(i)),abs((r_min+(1-(i-22.5)/112.5)*(r_maj-r_min))*cos(i))]);
		}
	}
}

m5_thread(height=12);