use a file as your base steel
http://www.bladeforums.com/forums/sh...fe-From-a-File
and here is a video of someone doing it
https://www.youtube.com/watch?v=J_jM...R22sebeeODbp48
these are great for solid thick blade rigid knife, but if you want a flexible knife then use a saw blade. a old hand saw is great for a knife blade if you want it very flexible like a fillet knife but if you want something that is semi-rigid but still has "some" flex to it, then use an old circular saw blade