Building an extruder today!

So as part of the unit I need to build an extruder to force clay through. Think this process is important, not sure why yet. Best solution so far to use a manhole access hole, with a smaller access hole bolted inside, like the smaller section an an actual extruder. Found the gap too big and initially used a blue pipe to try and reduce the thickness of the clay but thought this would not be substantial enough therefore I have added rubber matting to make the clay thinner.