How to Polish a Knife Blade

Polishing out scratches in a steel knife blade just takes some sandpaper, Simichrome, and elbow grease.  I experimented with polishing by hand and came up with some simple recommendations.

There are usually 2 obstacles to getting any task done.  Not knowing where to start and worrying about “ruining” whatever it is you are working on.  I know how to sharpen a knife with a file and with a stone.  But I have not done much cosmetic work on knives.  So I decided to venture into knife repair, and learn how to remove scratches from a knife.  I started with a badly scratched kitchen knife because I didn’t care if I ruined the way it looked.  It was just a kitchen knife, not a rare collectible Bowie.  And also, this particular kitchen knife was really messed up.  It is a Gerber Balance Plus 1401 10” Cooks knife made of high carbon stainless steel.

 

scratched knife blade How to Polish a Knife Blade

More Scratches than Blade

badly scratced blade How to Polish a Knife Blade

Very badly scratched blade, probably from terrible sharpening technique.

scratches on blade How to Polish a Knife Blade

Scratches Scratches Everywhere

Please note, I did not scratch the bejesus out of this knife.   I got it second hand.  It is hard for me to imagine how a kitchen knife could become so damaged.  Pretty much every bit of the blade was criss crossed with big and little scratches.  But that made it a good place to practice.

Let’s review the rules of every DIY project:
Rule #1, get started.
Rule #2, don’t ruin it.

In the spirit of getting started without ruining it, I began my knife polishing project by trying Simichrome metal polish first.  I recently discovered Simichrome polish, which is a metal polish that also works on a variety of other hard surfaces.  It does a good job at really bringing out a shine, and it is very mild.  I thought I would try the mildest polishing technique in my arsenal first because that would have the least chance of damaging my blade.

simichrome polish 450x198 How to Polish a Knife Blade

Simichrome Polish is great for finishing the job, but don’t be afraid to start with something a little rougher to finish the job more quickly.

Though I could not feel the scratches on the blade with my finger, it soon became obvious that the scratches were too deep for Simichrome.

My next blade polishing technique was to use sandpaper.  I started out with 400 grit sandpaper.  That too turned out to be too mild to make rapid progress.  From there I moved down to 240 grit sandpaper.  The 240 grit did a nice job of removing about 80% of the scratches.  But many of the scratches didn’t seem to be much phased.

I then started working on the knife with 150 grit.  I really thought 150 grit would be too coarse, and that it might put deep scratches of its own in the blade.  But it worked nicely.  And if I had any 100 grit, I would have given that a try to speed things along.

After working for a while with 150 grit, I then moved back up through 240 grit, 400 grit, and then up to 1500 grit.  After the sandpaper I went back to the Simichrome polish.  The result is that the knife looks much much better than it did before.

shiny blade How to Polish a Knife Blade

This knife is much more shiny and smooth after polishing.

DSC 0002 002 How to Polish a Knife Blade

With most of the scratches removed, this is now a nice looking knife.

polished knife blade How to Polish a Knife Blade

The knife has gone from scratched embarrassment to mirror shine.

As you can see, I did not take out every scratch, mainly because I wasted so much time experimenting with added steps that I didn’t really want to back up to heavier grit and remove the last of the scratches.  But most of what remains is only visible in a very high contrast environment.  The knife looks almost new now, and I actually enjoy using it more now.  I didn’t realize that the ugliness of the blade bothered me before, but it did.

Here are my recommendations for polishing a knife blade that is badly scratched:
Don’t worry about causing more damage by using too coarse of a sandpaper.  Next time I will start the process by sanding with 100 grit sandpaper to remove the heavy damage quickly.  The way I did it, starting with the mildest, working all the way through to the roughest, and then back through to the mildest was very tiring, and ended up taking about 2 ½ hours.  Starting out with 100 grit and going up as needed would probably only take 1 hour or less.

Simichrome works well as a polish on metal and micarta.  The only problem I had was where to buy Simichrome polish?  Orchard Hardware (OSH) did not have it.  O’Reilly Auto Supply did not have it.  I finally found it at Ace Hardware, locked in a case.  The Ace guy, who uses Simichrome himself, told me that the company that makes it doesn not have a distributor, so stores need to order it directly from the manufacturer.  If your normal hardware store doesn’t have it, I would order it from Amazon (always support your local hardware store, or one day it will vanish, and your house will fall down for lack of one damn bolt on a Saturday afternoon).

Knife Polishing and Scratch Removal Supplies:
- 100 Grit Sandpaper
- 220 Grit Sandpaper
- 400 or 600 Grit Sandpaper
- 1000 to 1500 Grit Sandpaper
- Simichrome metal polish
- cloth diaper, old washcloth, or similar cloth for applying Simichrome
- disposable rubber gloves – optional but probably good to use when generating metal dust and using things like Simichrome.

Comments

  1. Can you do a video?

  2. lee holseberg says:

    As a motorcyclist since 1963, I’ve been using Semichrome for nearly 50 years. It’s always been readily available at most motorcycle shops, and works like nothing else to turn the aluminum look of brake and clutch levers into the mirror reflection of chrome. Never used it for scratch removal, seems much to fine to do the trick. Jewelers rouge in one of the numerous colors applied to a firm cloth polishing wheel on a grinder works pretty well on scratches, but stainless is a bitch to polish out no matter what you use. Good luck!

  3. Anonymous says:

    How much time do you recommend spending on each grit of sand paper? Is there some type of finish on the blade that you should look for to know when to switch to a milder grit? Thanks for this post, very helpful.

    • There are many variables in polishing a knife. The type of steel is going to influence how quickly blemishes can be removed. Hard steel is really hard to polish, and can take a lot of work. The only answer is that you need to experiment. See what works on your knife. If you can’t get a scratch out, move to coarser paper. If the blade is not getting any shinier, switch to finer paper. Let me know how it works.

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