I picked up 3 very used draw knifes at a flee market this summer. A friend made some new handles and I cleaned them up some. One is a Fulton 10 inch, another is marked ESSEX M 9 inch. The third does not appear to be marked. One appeared to have been used as a froe, the back spine rolled over from being hammered. I filed them smooth again and after cleaning them up noticed small chips on the edge. My question is how to best get the edges smooth again and how to sharpen them. I have read where some leave them dull for removing bark. Opinions?