Dstep = 71;
Margin = 3.125; // 6.35mill; 12.7mm bushing
Acutout = 55;

difference() {
  square([Dstep*5+100, Acutout + 100], center=true);
  for (i = [-2, -1, 0, 1, 2]){
    translate([i*Dstep, 0])
      offset(r=Margin)
        square([Acutout, Acutout], center=true);
  }
}