$fn=50;
difference() {
    rotate([90,0,0])
    cylinder(h=28,d1=5,d2=5, center=true);
    
        translate([0,-29/2,0])
        rotate([90,0,0])
        cylinder(h=10,d1=3,d2=3, center=true);

}

//keyway
difference(){
    translate([0,(-28/2)+4/2,-5])
        cube([3,3,7], center=true);
    
    translate([0,(-28/2),-4])
        cube([5,5,1], center=true);
    
      translate([0,(-28/2),-7])
        cube([5,5,2], center=true);
}