Skyline – Your GitHub story in 3D(skyline.github.com)

    The designer sat at his drafting board
    A wealth of knowledge in his head was stored
    Of what can be done on a radial drill
    Or a turret lathe or a vertical mill.
    
    But above all things a knack he had
    Of driving gentle machinists mad.
    So he mused as he thoughtfully scratched his bean
    "Just how can I make this thing hard to machine?"
    
    If I make this body perfectly straight
    The job had ought to come out first rate
    But it'd be so easy to turn and to bore
    That it never would make a machinist sore.
    
    So I'll put a compound taper there
    And a couple of angles to make them swear
    And brass would serve for this little gear
    But its too damned easy to work, I fear.
    
    So just to make the machinist squeal
    I'll make him mill it from tungsten steel
    And I'll put these holes that hold the cap
    Down underneath where they can't be tapped.
    
    Now if they can make this it'll just be by luck
    Cause it can't be held by dog or by chuck
    And it can't be planed and it can't be ground
    So I feel my design is unusually sound.
    
    And he shouted in glee, "Success at last!
    This goddam thing can't even be cast."