printer_offset = 0.5;
top_slot_width = 8;
top_slot_height = 2;
middle_slot_width = 14;
middle_slot_height = 7;

length = 20;

module T_nut(){
    translate([-middle_slot_width/2, length/2, middle_slot_height-printer_offset])
    rotate([90, 0, 0])
    linear_extrude(length)
    offset(delta = -printer_offset/3)
    polygon(
        [
            [0,0],
            [0, -middle_slot_height],
            [middle_slot_width, -middle_slot_height],
            [middle_slot_width, 0],
            [middle_slot_width - (middle_slot_width - top_slot_width)/2, 0],
            [middle_slot_width - (middle_slot_width - top_slot_width)/2, top_slot_height],
            [middle_slot_width - (middle_slot_width - top_slot_width)/2 - top_slot_width, top_slot_height],
            [middle_slot_width - (middle_slot_width - top_slot_width)/2 - top_slot_width, 0]
        ]
    );
}

module cylinder_outer(height,radius,fn){
   fudge = 1/cos(180/fn);
   cylinder(h=height,r=radius*fudge, center=true, $fn=fn);}

module hex(size, height){
    cylinder_outer(height, size/2, 6);
}

difference(){
    T_nut();
    cylinder(r=3+printer_offset/2, h=100, center=true, $fn=30);

    translate([0,0,-0.3])
    rotate([0,0,30])
    hex(10, 10);
}