It is just steel, the square part at the end for the key is quite easy. Just put 90 degree marks on the lathe chuck and then file your flats. It may take a little practice to get it right but take your time and do this first before then turning down the diameters for the barrel etc. the harder part is the tang that the mainspring clips over. This can be done by inserting a suitably sized steel screw into the arbour and then filing to shape.
Good luck 
Paul.
