I am finishing a small kife made from AISI 425 stainless steel (see http://www.duelknives.co.nz/spec.htm). It was all hand cut, filed and sanded to 400 or 600 grit before heat treating. After HT, I sanded starting at 240 grit and progressed through 400, 600, 1000 to 1200 grit. I used a micarta block to hold the sandpaper and alternated directions on each grit. Starting at 1000 grit, I could see some "milky grey" lines running roughly parallel to the blade, about 1/4 - 1/2 inch from the edge of the blade. I went back to 400 grit, thinking that there were scratches that I had missed. I am now back up to 1200 grit and these lines are still visible. They don't appear to be scratches since scratches can be sanded out and show up as a change in the surface level under strong light. These lines only show up at certain angles and appear to be some kind of coloration in the metal. What could these "lines" be? Could they be temper lines? Lane of Duel Knives did the heat treat over a year ago. I don't know if he did an edge quench. The knife has a 2 1/2 inch blade and is 5 1/2 inches overall, so I doubt it. Thanks in advance.
Phil
Phil
