screw with hex head

hexhead_screw.scad

// screw with hex head
// useful for modelling attachment bores
// with nut trap
// default values are for M3 (5.5mm head) screw 20mm (3.2mm bore for tolerance)
// param membrane thickness is for additional layer between head and shaft,
// for upside down printing, usually set this to your layer thickness
module hexhead_screw(
        length=20,   //per definition, excluding head 
        head_wrenchsize = 5.6,  
        head_thickness = 3,    
        screw_dia = 3.2,  //shaft dia
        support_thickness = 0    //support thickness, if any (default 0)
        )
{
    union() {
        cylinder(r = head_wrenchsize / 2 / cos(180 / 6) + 0.05, h=head_thickness, $fn=6);
        translate([0, 0, head_thickness+support_thickness])
            polyhole(h=length, d=screw_dia);
    }
}