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Sharpening a knife


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Hey guys, I've just started blacksmithing and have made a few knives, though I've only sharpened them with my cheap and extremely weak belt grinder.

I'm thinkin' about buying one of those "Japanese" knife grinding stones, but I don't know which one will work best for me.

I've made a few razors that I intend to make really sharp, and a few kitchen knives that could use some sharpening aswell. What I am looking at right now is a combination stone, meaning one grit on the top and another on the bottom, and my options are 240/800, 400/1500, 600/2000, 1000/3000, 2000/5000, 3000/8000.

I am only gonna buy one of the combination stones, cause I don't want to spend to much money on this right now, so which one do you guys think will work best in putting a nice, sharp edge on my blades?

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Time, patience, the proper ange and finishing on a leather strop or wheel with the proper buffing compound.  Many folks prefer using wet and dry paper over a stone, but thats personal preferance. 

Dont poopoo the strop it is the most important step. An engeniring paper was writen on it, I belive you can find a copy on bushcraft usa.

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Actually, you don't really need to invest in Japanese water stones to get a sharp edge,  The Japanese stones are specialist tools for refining the polish and texture of highly refined forging processes.  As for sharp Norton or other similar brands make stones that will sharpen steel as well as the best Japanese water stone. 

Time, patience, the proper ange and finishing on a leather strop or wheel with the proper buffing compound.  Many folks prefer using wet and dry paper over a stone, but thats personal preferance. 

Dont poopoo the strop it is the most important step. An engeniring paper was writen on it, I belive you can find a copy on bushcraft usa.

The leather strop will finish an edge to as fine as is possible by hand.  I bought a selection of Arkansas natural stones years ago that I've used to good effect. 

Remember the ultimate sharpness of a blade depends on the material from which it is made and the geometry.   Sharp also depends on the intended use.  A blade I use for slicing tomato's is not the kind of sharpness I need  a pocket  knife, or in a drill bit.     

Edited by Charlotte
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I own a wide selection of stones, both natural and synthetic - but I went over to diamond plates a few years ago and that's all I use now for general knife and axe sharpening.  However, razor sharpening is a different animal from knife work.  Strop is important but it takes quite a bit of foundation work to get to the point where the strop finishes the edge.

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Eons ago when I was in Jr High shop class we had to learn to sand and polish. The teacher hammered on us that you can't skip steps. You have to get all the marks out from the previous step before moving on to the next grit. The point being you can't jump from 80 grit sand paper to 400 grit and expect to get out the marks from the 80 grit with out a tremendous amount of wasted effort. Same applies to stones. They have different grits depending on where you are in finishing. You can't go from a rough grind to a 3000/8000 stone and expect good results. On the other hand  If you are finishing out at 1200-1600 grit wet dry sand paper a 240/800 stone probably isn't the one you want.

 

I keep a mid size diamond "stone" in the trim bucket with all my planes and chisels. ( I forget the grit right now) I use it to touch up the edges on my good trim chisels and planes any time they even start to get dull. However if I put a serious nick in a blade like what can often happen with my "junk" chisels when I have to work around nails and stuff, I don't even bother to pull out the diamond stone. It goes straight to the belt sander or grinder to deal with the heavy stuff. Then I may tough that edge up depending on the work I'm doing with it at the time.

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I shave with a straight razor pretty often, and I find I have to take mine up to an 8000 Norton stone to get them to a usable sharpness.  Otherwise, they just tear the hair out of my face.  As others have said, you can't go from 100 grit to 8000 in one jump.  You have to hit the grits in between.

I dry strop, but a lot of folks swear by using various pastes for this step.  

Stropping is a very different technique to honing, and honing a razor is quite a bit different from sharpening a knife.  It is very technique dependent, and isn't a process for someone who is easily frustrated by failure. ;)  There are lots of good guides on the shaving forums like "Badger and Blade" if you are up to the task.

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rhitee93

 

   Nice to know there is another person on the board that like a close shave :D.  I have about 5 razors in a rotation but when stropping no longer does the trick I send mine off and have them honed.  I have all of the stones, just not the skill or time to develop it!   I must second your statement that sharpening a knife is completely different than sharpening a razor!

 

Russell

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Hey Russell,

I hate face stubble, and go for a BBS shave every morning.  It's funny, but even though blacksmithing seems be dominated by dudes with heavy beards, I have bumped into a lot of fellow shaving enthusiasts on here and another forum I frequent.  

I only have a couple of straights that see any regular use, and I avoid going to the hone as long as I can.  My results aren't very predictable, but the last time I sent one out, i decided I liked my honeing better so I guess I am improving.

I have been getting lazy for the last several months and have been using a '20's open comb double edged razor.  The wife and kids take up a lot of morning time, and these days I tend to shave in the shower.  I won't use a straight without pants on! (or a towel)

best...

-Brian

 

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Rhitee,

 

    I just about feel out of my chair over your last sentence!! So true so true.  and until someone has shaved there face with a straight razor they just wont get it!!!

I shave after my evening shower because if I tried it in the morning I would need Thomas's SS apron, along with SS pants and boots!

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  • 2 weeks later...

I'm once again, late to the party. All the most important stuff has been said here. I'll just add a personal pointer. Seeing as how you mention both razors and kitchen knives. 

The essential difference between the two will be the level of polish. A kitchen knife needs to be a little less polished, because on a microscopic level, you want the edge to retain micro serrations. These micro serrations allow the knife to bite into what you are cutting, rather than glide on it. For instance, an over-polished kitchen knife will tend to slip on a tomato because of its skin, rather than cut into it like it isn't there. I've found my sweet spot on japanese stones for kitchen knives to be around 4000/6000. 

For a razor you need to polish it further. Hence the whole 8000 and strop, and the much feared honing process. A razor needs to be highly polished in order to eliminate said micro serrations, mainly because you want the razor to glide on your skin, certainly not tend to bite into it. 

That's essentially the tl;dr of edge properties as was explained to me by a guy who makes a living sharpening kitchen knives and straight razors with japanese water stones. His advice was gold. My sharpening skills saw a lot of improvement anyways. 

Hope this if of help. 

-Cheers

Pat.

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All good advice , I would go to your local hardware store and get a cheap stone to practice with. After some practice I am getting great results with a $5 stone. Not suitable for a razor but a fine edge for a knife , with more time finishing it could be but why do that for a knife, first couple cuts threw something tough and the razor edge is back to being just sharp. It doesn't take anything fancy to get a good sharp knife edge , just patients and consistency of the angle.

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I worked with a guy who did the final wire edge strop on a piece of corrugated carton paper.  The surface is really abrasive and will wear out an edge quickly so he reasoned it would be good to use for a strop.  I've tried it a few times and works pretty well - especially on softer blades like kitchen knives.

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Got that one to Jerry, figured it was my ham fingers, small toichscreen and low tech skill set. 

I started to put a peice of duct tape on the inside of my belt so Sandy stoped grouching about the stanes on my britches. Hech, i figuered as my belt coverd them who would be the wizer?!

At home i have a peice of skirting leather glued to a block of wood as a strop, in the feild its the back of my belt were a bit of rough is hidden under that bit of tape. 

Coffee burns the sinuses, don't it?! Lol

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I've used the bottom of a cup (ceramics/pottery) the unglazed ring to final sharpen a knife and the ground edge of car window to strop it before now.

However I generally sharpen my knives with the common twin grade wet/oil stone (I prefer oil). To the subsiquent "oily dust" created I add more oil and use it applied to a slither of copper for polishing blades (similar to the technique employed by Japanese sword sharpeners). It's a long laborious process which I find particularly satisfying!

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One of my woodworking mentors recommended using soapy water as a lubricant for sharpening with oilstones. You get the same sharpening effect, but you can then rinse the slurry off the stone and not gum it up with oil and metal particles.

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