Polishing Tips

W

Waco Kid

Joined
Apr 7, 2006
Messages
91
I'm polishing up some blades, to a either a shiny satin or mirror finish. I've never done this before, but as I understand it, I simply use progressively finer grit sandpaper. I assume circular motions would be best (for mirror), and I haven't the foggiest how to make the lines straight for a satin finish (looks wavy). Anyway, should I lightly oil the blade or just go dry?

Any other tips are also appreciated!
 
Don't use circular motions. Use wet/dry automotive paper wrapped around a paint stirring stick. Start at 320 grit. Finish at 2000 grit. Use water with a drop of detergent. You're in for a surprise!
Bill
 
Overlay your grits in different directions. Run the first set <--->. when you switch to the next grit go |. Go over until all the previous stroke etch marks are gone. Alternating the direction with the grit change helps in getting out all the scratch pattern from the previous grit. You can use different shapes/sizes of wood to wrap the abrasive paper around to get in where you need to go.
 
Use a random polishing motion only when you get to the sub-micron grit sizes (if you ever go that fine). Anything much above that you will be able to see still scratches which look a lot better when they are straight.
 
Great advice. Thanks!

The blade is carbon steel -- so is the water and detergent still ok?

-kid
 
You could use WD 40 instead, if you are worrying about rust.
Bill
 
Windex works good too.
Progressive grits of sandpaper 320 - 2000 is fine for satin, however isn't a electric buffer required for a true mirror finish?
Anyway, I havn't been successful with paper for a mirror finish.
 
More good advice. Good link too -- highlighted another mistake I was making...

"Soft pads or fingertips don't work for sanding on hardened steel. The idea is to have the block level things off, not to follow the small irregularities in the metal that are already there."
 
Kevin Jones said:
Windex works good too.
Progressive grits of sandpaper 320 - 2000 is fine for satin, however isn't a electric buffer required for a true mirror finish?
Anyway, I havn't been successful with paper for a mirror finish.
Click to expand...

The ammonia kind... definitely not the Windex with vinegar (acid tends to promote rust while bases tend to inhibit it)
 
Waco Kid said:
More good advice. Good link too -- highlighted another mistake I was making...

"Soft pads or fingertips don't work for sanding on hardened steel. The idea is to have the block level things off, not to follow the small irregularities in the metal that are already there."
Click to expand...

You may not have the elbow grease to get a blade perfectly flat (depending on size of the blade and the particular steel you're polishing, and whether the value of the knife warrents all the work involved) without resorting to a soft backing on the finer grits. I've tried blade polishing on diamond plates and stones (a 5,000 grit waterstone will leave a slightly hazy mirror finish, 8,000 will tend to look like a mirror with a tiny bit of moisture condensation on it and 10k-15k tends to look bright and deep like a first-surface mirror) and find that most blades are full of waves and dents so you wind up with a very spotty polish with shiny high spots and dull low spots... then you have to go back to the coarse grits and start all over and hope you've ground off enough to make things flat enough to polish evenly. That can get real old after about the 3rd time! So, do as much flattening as possible on the coarse grits (diamond plates, freshly flattened stones, loose grit on an iron kanaban grinding plate or coarse sandpaper on a surface plate or other hard and very flat surface.) If you were careful and did a great job with the coarser grits, you should wind up with a nice even polish. If you've ground your arm off and still wind up with a slightly spotty polish (and are too tired to start over, or maybe it just isn't worth it for a cheaper knife anyway), you might find that something a bit softer, like buffing compound or diamond paste on leather glued to a block of wood, or something similar, will get down into the slight depressions and polish them up as well.
 
I was just using my fingers and dry sandpaper -- boy did they get hot! Good thing they're pretty calloused...
So I guess I'll just wrap/staple the sandpaper to a wood block. That should be hard and flat enough, right?
If its not perfect -- that's fine, I'll just leave it a little satin...
 
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