Getting a Better Grasp on Finishing/Shining

[LibrariaNPC]

My experience with this isn't really that great, so I'm looking for some input that will hopefully get me on track here.

After I finish the heat treat process on a blade, I normally do a quick pass with sandpaper (usually 60-80 grit) to get rid of any excess gunk/missed oil/char, soak it in vinegar, lock it into a vice or onto a board (which is locked into the vice) and work with an angle grinder with progressively higher grits. Afterward, I do some sanding by hand (next highest grit I have) and move up to a point I like the shine.

My first time making a blade, I didn't have to do much sanding by hand, and got away with few (if any) visible scratches, and my smaller knives have been moving along pretty well without issue. My first time making something bigger (a sword) only had a few minor scratches that I couldn't remove without risking making the material too thin (already a thin blade). I've had good luck so far, I think, but I'm at a bit of a snag.

Now I'm working on a project (pictured) that seems plagued with scratches that I can't get rid of, and each time I work on it (either with an angle grinder or sandpaper), I'm finding scratches elsewhere that weren't there before (in this case, closer to the spine). This particular project, a costume piece, is forged from mild steel (was specifically requested to not use high carbon steel), so I'm not sure if that makes a difference in this case (too soft and easily scratched?).

I'm not sure if I'm doing something wrong (because if I have a bad habit, I wouldn't be seeing it) or if I'm not using the correct tools for the job (or not using said tools correctly).

 

Any input involving experience with cleaning up a blade or other projects to a nice polish (mirror or otherwise) would be greatly appreciated!

[Charlotte]

Being meticulous  in cleaning up after each step helps prevent the mystery scratches.    That applies to all phases and materials to be polished.  If a new scratch appears you have to go back to the grit that caused it to remove it normally.  Yes, soft materials are a bit more difficult to polish and require softer grits.  Jewelers rouge seems to work on most mild steels in my experience.  A soft muslin buffing wheel would help.

Edited October 15, 2015 by Charlotte
word left out

[LibrariaNPC]

I lack a proper buffing wheel; I have a sort-of buffing wheel for my battery powered drill, but it doesn't seem to get to the necessary speeds to do much.

Any suggestions on a specific grit? The highest grit sandpaper I have at the moment is 1200, and I know nothing about jeweler's rouge outside of it is normally used with a buffing wheel (and again, not sure if my drill can do what is needed).

Thank you for that input!

[j.w.s.]

Try changing your directions when you sand. We touched on it in class, but there was a lot of information covered over those two days and you were finishing two knives! Let's think about it two dimensionally. If you start sanding x1 to x2 then go y1 to y2, then to diagonally between x1 and y2 and lastly x2 to y1.. essentially cross-hatching your scratches which will blend them and give you a nice finish. Otherwise, any deep scratches you see, you can step back a grit and try to remove, if it doesn't work, step it back again - repeat until it's gone, then start stepping up again.

J

[LibrariaNPC]

So, with this piece, I should lock it into the board, sand diagonally (say top left to bottom right), then once it's been scratched up, approach it from a different angle (say top right to bottom left), and once it looks like it's blended, move up a grit?

Just making sure I'm grasping this correctly. I was trying the diagonal approach with the 500 grit this morning for about 30 minutes but didn't look like I was making much progress, so just trying to make sure I'm not missing a step somewhere before I try again (or pick up a tool I don't really need).