When do I stop polishing?

[Noctis3880]

Here's a short list of polishing tools I have:
-60 grit 3M sandpaper.
-80 grit 3M sanding sponge.
-100 grit 3M sandpaper.
-Micro-Mesh metal finishing kit(100MX-1200MX micro-mesh abrasives).
-Micro-Gloss(data says it's a 1 micron aluminum oxide liquid abrasive).
-200,000 mesh diamond spray(bought for $11 a bottle from PrettyRock.com so I'm not sure if it's real diamond).

Since a week ago, I've been spending considerable time sanding off the BK coating from my BM 943SBK blade. However, there are still some faint lines near the tip of the knife running from the spine to the edge. There are even fainter scratch marks running from the tip to the handle due to my method of sanding and polishing, which involved holding the wet abrasive in my hand and basically "pinching" the blade between my thumb and forefinger and moving it from one end of the blade to the other continuously.

I have a foam sanding block, but I'm afraid to use it because I don't want the edge or tip of the blade to accidentally puncture the abrasive, not to mention that I'd only be polishing one side at a time instead of both at once.

The final finish is done with micro-gloss and then the diamond spray with a micro fiber cloth.

The finish right now is pretty shiny, but the lines are pretty obvious up close, or under a good light source(like the flash from a camera). I've been wondering about whether it's even possible to put an even finer finish on the S30V blade, or whether it would just be "an exercise in futility".

The strange thing is that the scratches seem to be either more numerous or more noticeable after using the micro-gloss.

I also plan to do this hand polishing on my Endura with ZDP-189(THAT'S going to be fun) as soon as I get it back from Tom Krein. I was considering simply buying more diamond sprays in different mesh sizes between 1 micron and my current 200,000 mesh(1/10 micron).

 

[Jason B.]

Here's a short list of polishing tools I have:
-60 grit 3M sandpaper.
-80 grit 3M sanding sponge.
-100 grit 3M sandpaper.
-Micro-Mesh metal finishing kit(100MX-1200MX micro-mesh abrasives).
-Micro-Gloss(data says it's a 1 micron aluminum oxide liquid abrasive).
-200,000 mesh diamond spray(bought for $11 a bottle from PrettyRock.com so I'm not sure if it's real diamond).

Since a week ago, I've been spending considerable time sanding off the BK coating from my BM 943SBK blade. However, there are still some faint lines near the tip of the knife running from the spine to the edge. There are even fainter scratch marks running from the tip to the handle due to my method of sanding and polishing, which involved holding the wet abrasive in my hand and basically "pinching" the blade between my thumb and forefinger and moving it from one end of the blade to the other continuously.

I have a foam sanding block, but I'm afraid to use it because I don't want the edge or tip of the blade to accidentally puncture the abrasive, not to mention that I'd only be polishing one side at a time instead of both at once.

The final finish is done with micro-gloss and then the diamond spray with a micro fiber cloth.

The finish right now is pretty shiny, but the lines are pretty obvious up close, or under a good light source(like the flash from a camera). I've been wondering about whether it's even possible to put an even finer finish on the S30V blade, or whether it would just be "an exercise in futility".

The strange thing is that the scratches seem to be either more numerous or more noticeable after using the micro-gloss.

I also plan to do this hand polishing on my Endura with ZDP-189(THAT'S going to be fun) as soon as I get it back from Tom Krein. I was considering simply buying more diamond sprays in different mesh sizes between 1 micron and my current 200,000 mesh(1/10 micron).

1/10 is way too overkill get more grit in between and keep them closer together and your results will be better. You finish should be a perfect mirror by 1 micron.

 

[Noctis3880]

Strange. I can see my eyes reflected on the blade, but it's still a little blurry.
I have about 9 different grit Micro-Mesh sheets going from coarse to fine. I typically spend about 5 minutes per sheet, but maybe I'm going through them too fast.

The instructions suggest going from horizontal to vertical and vice versa between grits to better keep up with consistency, but someone warned me that it would undo a lot of the work if I cross polish. Also, going to a coarse grit from a finer grit doesn't seem to make much of an obvious difference, as I can barely notice a difference in scratch marks. I also don't plan to spend another hundred for a microscope just to see the scratches(not quite THAT obsessed about knives).

Maybe I should stretch it to 30 minutes to an hour per grit? Or would that be overkill? I think I'll try it along with the foam sanding block tomorrow after I fix the edge so that it can actually cut again(rough work with the 60 grit destroyed the edge).

I also figured maybe an hour or two of buffing with the Micro-Gloss would do the trick.

1/10 micron might be overkill, but I wanted something with a PERFECTLY smooth surface(no lines visible to the naked eye). Diamond was suggested for relatively faster cutting/polishing action, and also because it's been stated that vanadium and niobium carbides are possibly harder than most abrasives, or at least hard enough to make attempts at polishing beyond tedious.

I'm also curious as to whether or not it would be worth buying more diamond sprays in different mesh sizes. I also wanted to know if there was some quick and easy way to tell if it's real diamond.

 

[Bill DeShivs]

Each sucessive sanding grit must remove ALL the lines from the previous grit.
60 & 80 grit is too coarse to start with, so you actually put scratches in the blade.
Use plain wet/dry automotive paper from 320 grit to 2000 grit.

 

[nksmfamjp]

I'm not speaking from knife experience her, but metal working is metal working. First, 60 - 200 grit is too rough for finish work. When you mention the blurriness, you clued me in on what might be going on.

So, when a company puts a dull coating on a product, they can reduce a lot of cost in the metal work. First a dull coating can go on something rough shaped and polished to about 320 grit and look great. So, that means that you the finish remover must first flat file the knife to get the shape right. Once the file is cutting without low spots, stop. Recutting the shape is key. Then move to 220 grit wet. Sand with support initially and then do the contours freehand. Sand wet until all file marks are removed. Then lightly resand the entire surface to minimize the cut depth of the 220 grit. Keep the knife rinsed off often to avoid grit falling off the paper and scratching the knife. You switch to the next higher grit when all the scratcches from the previous grit are gone and all the new scratches are of the current grit.

Then, do the same with 320, 400, 600, 800, 1000. At 1000, this should be mirror bright. Now decide if you want mirror bright or lightly sand in a pattern with the grit pattern you want as a finish.

If you want mirror bright, switch to a powered buffer with the appropriate compound for your knife's material. Again, knives are so hard, I'm not sure what to use.

Sanding without support or with power will be a crap shoot

 

[Noctis3880]

Just to let you know, the Micro-Mesh MX grits are different from the standard grit sizes.

I believe the coarsest one I have(100 MX) is the rough equivalent of 320 grit wet/dry sandpaper at between 42-45 microns.

However, I did switch from conventional sandpaper to the Micro-Mesh at 100 grit to 100 MX(from 100 to 320), so I guess I'll have to close that gap before I get anywhere.

The finest grit Micro-Mesh is 1200MX, which has a grit size of 3 microns. From that point on I go with Micro-Gloss at 1 micron and the diamond spray at 1/10 microns.