module screw(type = 2, r1 = 15, r2 = 20, n = 7, h = 100, t = 8)
{
	linear_extrude(height = h, twist = 360*t/n, convexity = t)
	difference() {
		circle(r2);
		for (i = [0:n-1]) {
				if (type == 1) rotate(i*360/n) polygon([
						[ 2*r2, 0 ],
						[ r2, 0 ],
						[ r1*cos(180/n), r1*sin(180/n) ],
						[ r2*cos(360/n), r2*sin(360/n) ],
						[ 2*r2*cos(360/n), 2*r2*sin(360/n) ],
				]);
				if (type == 2) rotate(i*360/n) polygon([
						[ 2*r2, 0 ],
						[ r2, 0 ],
						[ r1*cos(90/n), r1*sin(90/n) ],
						[ r1*cos(180/n), r1*sin(180/n) ],
						[ r2*cos(270/n), r2*sin(270/n) ],
						[ 2*r2*cos(270/n), 2*r2*sin(270/n) ],
				]);
		}
	}
}

module nut(type = 2, r1 = 16, r2 = 21, r3 = 30, s = 6, n = 7, h = 100/5, t = 8/5)
{
	difference() {
		cylinder($fn = s, r = r3, h = h);
		translate([ 0, 0, -h/2 ]) screw(type, r1, r2, n, h*2, t*2);
	}
}

module spring(r1 = 100, r2 = 10, h = 100, hr = 12)
{
	stepsize = 1/16;
	module segment(i1, i2) {
		alpha1 = i1 * 360*r2/hr;
		alpha2 = i2 * 360*r2/hr;
		len1 = sin(acos(i1*2-1))*r2;
		len2 = sin(acos(i2*2-1))*r2;
		if (len1 < 0.01)
			polygon([
				[ cos(alpha1)*r1, sin(alpha1)*r1 ],
				[ cos(alpha2)*(r1-len2), sin(alpha2)*(r1-len2) ],
				[ cos(alpha2)*(r1+len2), sin(alpha2)*(r1+len2) ]
			]);
		if (len2 < 0.01)
			polygon([
				[ cos(alpha1)*(r1+len1), sin(alpha1)*(r1+len1) ],
				[ cos(alpha1)*(r1-len1), sin(alpha1)*(r1-len1) ],
				[ cos(alpha2)*r1, sin(alpha2)*r1 ],
			]);
		if (len1 >= 0.01 && len2 >= 0.01)
			polygon([
				[ cos(alpha1)*(r1+len1), sin(alpha1)*(r1+len1) ],
				[ cos(alpha1)*(r1-len1), sin(alpha1)*(r1-len1) ],
				[ cos(alpha2)*(r1-len2), sin(alpha2)*(r1-len2) ],
				[ cos(alpha2)*(r1+len2), sin(alpha2)*(r1+len2) ]
			]);
	}
	linear_extrude(height = 100, twist = 180*h/hr,
			$fn = (hr/r2)/stepsize, convexity = 5) {
		for (i = [ stepsize : stepsize : 1+stepsize/2 ])
			segment(i-stepsize, min(i, 1));
	}
}

translate([ -30, 0, 0 ])
screw();

translate([ 30, 0, 0 ])
nut();

spring();