polishing knives

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Readyrod

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I have a couple of blades with scratches on them from sharpening with a diamond sharpener.(and other reasons) I've polished a few of them out with simichrome polish and it works but it is a lot of work by hand. Anybody have any suggestions about how to polish out scratches on a blade with a power tool? Please excuse my ignorance but I've worked a lot with hand tools but not with power tools. I'm looking for a simple compact solution as I don't have a lot of space.
Thanks RR
 
I don't know of any simple solution.

Scratches have to be hand rubbed / block sanded out using black Wet or Dry emery paper and oil.
Start out with 240 grit, then rub cross grain to get those scratches out with 320.
Then cross gran of those scratches with 400.

By then, the finish is fine enough to move to a 6" or 8" powered cotton buffing wheels and progressively finer grades of buffing compound.

It's a lot of hard work, but you can produce a true mirror finish if thats what you want.

You can't use a Dremel tool felt bob without leaving swirl marks that look worse then the scratches.

rc
 
One of the most dangerous things you can try is to use power tools to polish out scratches on a knife. Dangerous in the traditional sense that you don't want to have the thing snatched out of your grip and then thrown and in the sense that you can do a lot of harm to the finish in a hurry.

In addition to hand polishing you can try an advanced technique using a palm sander modified to aid in polishing. You'll have to make a jig to hold it level securely facing up and strip off any padding so you can mount the fine polishing paper RC referred to, but you can use it to increase the rate of work without the risk of a rotating wheel.
 
The same way I told you about in post #2.
Hand rubbing the belt grinder marks out a freshly ground blade blank with progressively finer grits of black emery paper & oil.

Manufactures expedite the process with diamond hones, media tumbling, precisely formed buffing wheels that conform to a hollow grind blade, and various other methods well beyond the home shop.

More lately, they just cover them up with baked-on finish of some kind.

The problem with polishing scratches out with common buffing equipment is, the buffing wheels tend to conform to the scratches and polish the bottoms of the scratches at the same rate as the tops.

So you just end up with mirror polished scratches that are still there.

Hand rubbing to remove enough flat surface metal to get the fresh steel below them, and then buffing is the only way I know of to do it at home.

rc
 
One of the most dangerous things you can try is to use power tools to polish out scratches on a knife.
Click to expand...

This above all - no knifemaker will take a sharp knife to any kind of buffer/polisher/grinding machine or they are nuts.

Be sure to dull the knife if you use any type of power tool to it. I'd do what RC said and use a block that fits the knife and sand it down and polish it that way and then use buffing compound or some kind of polish on it.
 
How do Knifemakers polish out scratches, hours and hours at the bench.

PTknifeWIP004_zps324f4d15.jpg

Also most do not do a mirror polish, they tend to scratch easily and look bad fast. Hand rubbed finish is best.

I am glad to see someone said don't put a sharpened knife to a powered polisher. A buffer will grab the blade and throw it across the room. If your in the way it will do some serious damage.
 
Semichrome will mirror polish your blade for sure. But it will take you months of work going about it like that. Start with at least 220 grit at right angles to the scratches you want to remove. Once they are gone change to 320 or 400. Sand at right angles to the previous grit. Once all those are gone switch to the next higher grit, up to 600 or 800. Once at your highest grit sand the length of the blade. If you start at the ricasso and pull straight to the tip, lift just before it drops off the tip. Keep this up until all the last scratches are gone and you have a nice even finish.

This is what knifemakers do to get the hand rubbed finish. By all means please kill the edge before you do this. Can't stress it enough. Seen way to many sliced hands and fingers.
 
Off to the toy store, I mean homecenter, I go. Sandpaper section.
Btw I've been thinking of getting a stone to use instead of the diamond sharpener. The homecenters here have a lot of choices (shelves and shelves of stones) and I'm not sure what to get/look for. Any suggestions?
 
None of the stones at the big box store are recommended because they'll be inferior to what you should buy for knives.

Go to the knife supply folks or get a nice slab of FLAT steel and use papers.
 
Actually you might need a couple. Find one in the coarser range with a medium grit on the other side, 220-800 then get a 1000-6000. This way you can get any type edge you want. Utility edge or super fine.
 
If the primary grind is not perfectly flat, it will take a long time to polish out scratches with a stone. You will need to start with a very coarse stone. Most all knives aren't perfectly flat. Many coarse stone are also not perfectly flat and/or they will go out of flat, quickly. So this is likely hours on hours of labor.

A quicker way to do it is to just use sandpaper. That follows the contours of the primary grind, imperfections and all. Start with the highest grit that will remove the scratches in question. You will need a sanding block to get the tip and the part of the blade next to the ricasso, but using just a finger you can get out the more accessible scratches quite quickly. Progress through your grits and finish on the strop. Set the knife on a block of wood so the edge on that part of the knife you are working on rests against the wood, and you will not damage the edge - or your finger. You can also you a dowel or a Bic lighter as a sanding block. A rod shape will follow most of the imperfections, but won't round off the edge bevel or spine.

None of the stones at the big box store are recommended because they'll be inferior to what you should buy for knives.
Click to expand...
I agree, those cheap manmade stones mostly suck. The Smiths Arkansas stones you see at the box stores are mostly ok. But even a soft ark is way too slow to remove scratches, though. A soft ark would be good for starting on the finish.... assuming your primary grind is perfectly, perfectly flat.
 
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If he's in Japan there aren't any "big box" mediocre stones and he can find some remarkable water stones and papers to work with.

That follows the contours of the primary grind, imperfections and all.
Click to expand...

Incorrect.

A paper has to have a flat backing, either a stone, piece of ceramic/flat steel, or float glass because any soft backing will introduce irregularities. It will NOT follow the surface with and consistency. Anyone can see that. What a properly backed paper will do is take an uneven surface down to a flat even surface just as any abrasive will take the high spots off and leave the a flat surface. That then has to be polished out by progressively finer papers/stones, but it ALL has to be backed by a flat surface supporting the abrasive to remove the high spots to the flat.
 
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Once upon a time in another land and time, I was on an overseas assignment and my wife need a knife to trim some rose bushes. She found a nice sharp D'Holder and went to work. The sap from the rose buses actually etched the blade. It was my wonderful wife so I did not get mad, I just made sure she had a full set of cutting instruments from then on. On my knife, I started with 300 grit, then 400, then 600 and finished off with 1200 grit. That D2 tool steel is hard stuff. It took a few hours but when I finished I had the knife back in original condition and was still married. ( pushing 45 years now ). Hey, why go ballistic, it was only a custom knife. She did learn not to use certain items that belonged to me, but it all worked out.:)
 
I used my fingers to follow the curve of the grind, a flat backing would not have worked in this case. I did use a backing for the blade flat, but there was very little damage there. On the curve I did use a small eraser as backing to prevent waves. Most of the damage was not deep and very little material needed to be removed.
 
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Sorry I've been busy. I was thinking of a stone for sharpening not getting the scratches out. If I have time I'll go to the home center tomorrow and see what they have. There are two large home centers and one very large home center in the area but, this being Japan, sometimes the selection is weird. I'll take some pix if I can.
 
There are plenty of sword polishers. get some drinks to share and go ask their advice/help.
 
That's an interesting point! This could be an opportunity to get with a Japanese polisher and see how they do these things (finger stones). They're not unapproachable and as craftsmen they like a good drink or three.
 
It will NOT follow the surface with and consistency. Anyone can see that.
Click to expand...
Well, there's perfect, and there's less perfect. You don't need to flatten the entire surface to remove some scratches. Every time you get a few new scratches, will you repeat the whole process? You won't have a lot of time left for anything else. And 10 years down the road, you won't have much knife left to show for your new full-time profession. :)

I do this on most all my uncoated flat and convex knives, at some point. On my fully convexed knives, I do this quite often, after a full resharpening. If the profile has been ruined, I would need to use some special equipment to figure out how bothered I should be, so I could calculate how much sleep I should lose. :)
 
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