School me on some sharpness stuff..

T

Technohedge

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Sep 9, 2018
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So Im getting into straight razors, I made my first one and honed it with stones to 8000k. In researching, I see all this stuff about people who have hunting knives (presumably with terminal edges much thicker than you'd' want a razor blade) who say they will shave arm hair. Some even claim it will do this straight off a 220 grit stone?

Now I know its NOT a functional necessity for that type of knife to be that sharp, but I cant (as yet) get a knife I have made for kitchen or field use to shave hair. Im talking 20 ish degrees per side, using an oil stone at 100 grit then 350 grit to put the edge on and removing the burr on a leather strop with compound on.

The sharpness i get is great for the knives intended use in the kitchen, but am I missing something with not getting them as sharp as others say they are, or are others putting edge geometry thats unsuitable for the job on their knives for effect?

Its not a big issue I'm just eager to expand my knowledge :
 
Examining your edge with a 10X or 20X loupe or scope may answer your question. It is possible you are still leaving part of the wire intact.

I think most of us have no issue getting a kitchen knife hair shaving sharp. I use a lower angle than 20DPS, usually around 15DPS. I sometimes just use a 220 grit belt and other times a 400 grit belt. I quickly buff the edge wire off and cut some cardstock to remove the final wire. By the third cut through the cardstock the blade is hair shaving sharp.
 
How thin are you grinding your knives before putting the edge on? It can make a difference if your leaving your knives too thick then putting an edge on it may be harder to get them as sharp as they could be. A common mistake is not fully forming a burr or holding a consistent angle while freehand sharpening. I use a coarse Norton India stone, I think it’s 150 grit then a fine stone that is 400 followed by a strop with green compound on it. If I can’t slice magazine paper with the 150 grit then I know I don’t have the edge where it should be and I won’t move up to the finer stone until I can do a slicing cut along the entire edge, by the end of the process with a strop I should be able to push cut the same paper with most knives other than heavy choppers.
 
i agree with the guys, i bet you are not getting a burr, or not removing it. learn the feel the burr with the edge of your fingernail, moving away from the edge on the underside of the blade.. you have to feel the burr all long the edge before turning the blade over to do the other side, and before switching to a finer grit. a more shallow angle will not help shaving if you re not getting the burr. i use the 30 degree slot on a lansky sharpener, it still shaves my leg hair easily even with the high angle. leg hair is harder to shave than arm hair, and i personally like the 30 degree angle because it lasts much longer than a 20 degree edge for general usage.
 
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I use a wicked edge to put the edge on my knives and have never had trouble getting them to shave, even at higher edge angles. I agree with the others that it’s more than likely you’re not drawing a burr along the entire edge of the knife.

As an aside, Stacy mentioned using belts to sharpen his blades. I’ve been terrified to even try that as I’m afraid of overheating the edge and losing my temper. For those of you that sharpen on a belt grinder, would you care to explain your process? If I could do that, I think it would save a tremendous amount of time. It takes me about 2 hours or so to go from a blunt heat treated edge to shaving sharp on my wicked edge. I have a VFD controlled belt grinder. Is the key to sharpening on it running the belt extremely slow?
 
Blackdirt cowboy said:
I use a wicked edge to put the edge on my knives and have never had trouble getting them to shave, even at higher edge angles. I agree with the others that it’s more than likely you’re not drawing a burr along the entire edge of the knife.

As an aside, Stacy mentioned using belts to sharpen his blades. I’ve been terrified to even try that as I’m afraid of overheating the edge and losing my temper. For those of you that sharpen on a belt grinder, would you care to explain your process? If I could do that, I think it would save a tremendous amount of time. It takes me about 2 hours or so to go from a blunt heat treated edge to shaving sharp on my wicked edge. I have a VFD controlled belt grinder. Is the key to sharpening on it running the belt extremely slow?
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I like using 3m ceramic 707 belts they come in 180 and 220 that work well for my Initial edge, you can run your grinder slow and use light pressure and don’t sit in a spot for very long, quick smooth motions work best. I use a single speed grinder and don’t have issues but I’m careful.
 
Blackdirt cowboy - FWIW ... I use a 400 grit belt running very slow (10 on the vfd), and run it wet. If water does not pool no the blade as it runs, I spray more water onto the belt. I also made a little angle guide (just mdf with a 15 degree side) that I use to set the angle of the blade relative to belt .. but then push that aside and hold that angle manually while I sharpen. When I have a burr along the entire edge, I then remove the burr with a leather belt (again on very low speed). The whole process takes maybe 15 minutes. Some might argue I am still heating the edge compared to using, say stones, ... and I might well be ... but at this point I am not interested in going for that level of edge performance
 
Blackdirt cowboy said:
I use a wicked edge to put the edge on my knives and have never had trouble getting them to shave, even at higher edge angles. I agree with the others that it’s more than likely you’re not drawing a burr along the entire edge of the knife.

As an aside, Stacy mentioned using belts to sharpen his blades. I’ve been terrified to even try that as I’m afraid of overheating the edge and losing my temper. For those of you that sharpen on a belt grinder, would you care to explain your process? If I could do that, I think it would save a tremendous amount of time. It takes me about 2 hours or so to go from a blunt heat treated edge to shaving sharp on my wicked edge. I have a VFD controlled belt grinder. Is the key to sharpening on it running the belt extremely slow?
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I use a Wicked Edge (WE) also, but I'm way faster.
Do you have the 50/80 grit stones to get started?
How thin do you take your edge before going to the WE?
 
Technohedge said:
So Im getting into straight razors, I made my first one and honed it with stones to 8000k. In researching, I see all this stuff about people who have hunting knives (presumably with terminal edges much thicker than you'd' want a razor blade) who say they will shave arm hair. Some even claim it will do this straight off a 220 grit stone?

Now I know its NOT a functional necessity for that type of knife to be that sharp, but I cant (as yet) get a knife I have made for kitchen or field use to shave hair. Im talking 20 ish degrees per side, using an oil stone at 100 grit then 350 grit to put the edge on and removing the burr on a leather strop with compound on.

The sharpness i get is great for the knives intended use in the kitchen, but am I missing something with not getting them as sharp as others say they are, or are others putting edge geometry thats unsuitable for the job on their knives for effect?

Its not a big issue I'm just eager to expand my knowledge :
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So the thing to keep in mind here is:

The grit of stone used does not determine if an edge will shave hair - it determines how comfortably it will shave hair. An 1000grit edge is alot more comfortable to shave with than a 220grit edge - but - that 220 grit edge will last much longer.

Geometry (how thin your edge is) is the greatest determining factor of whether an edge will shave hair or not. If you can't shave with your 120 or 220grit edge to begin with ... taking it up the grits will not make it cut any better.

As for you being unable to get your kitchen knives shaving sharp - how thick are your kitchen knives behind the edge? It is very easy to get a (for example) paring knife made out of .065" stock shaving sharp - assuming there is actually a decent grind on the knife that leaves 15-20 thousandths of an inch behind the edge.
 
I’m just scared to go any thinner. I’m pretty new to knife making and I’m afraid I’ll ruin the temper on the edge.
 
Blackdirt cowboy said:
My coarsest Stone is 100 grit. Usually I’m .03” thick on the edge when I start.
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If you are doing a flat ground blade .03 is on the thicker side, you could take it down to .01 in my opinion. Flat ground blades get thick faster and have more meat behind the edge. I leave heavy chopping knives at .03-.04 then convex
Blackdirt cowboy said:
I’m just scared to go any thinner. I’m pretty new to knife making and I’m afraid I’ll ruin the temper on the edge.
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dont grind one side all the way then the other, grind a 45 degree bevel on one side down to a scribe line then the other, by grinding two steep bevels you won’t have to worry as much about over heating cause the material behind those short bevels help pull heat away from where you are grinding, also don’t put direct pressure on the edge, I always keep direct pressure on the middle of the blade then use my other hand that’s holding the handle to control the grind by twisting or applying rotational pressure. Overheating happens quickest if you are directly pressing behind where the abrasive is contacting.
 
That makes sense. So far if only done hollow grinds. I couldn’t go much thinner on the edge otherwise I would’ve ground through the middles. But I can see where a flat grind would benefit from a thinner edge. Unless of course it’s a chopper or a blade that will be subject to abuse.
 
Im definitely forming a burr, I can feel it all along the edge, I think im having more of a problem removing it fully. I have a great leather strop, bit sometimes i still feel a burr. Have tried pulling the edge through soft wood even, still feel a burr there. Is the burr im creating too heavy?
 
Technohedge said:
Im definitely forming a burr, I can feel it all along the edge, I think im having more of a problem removing it fully. I have a great leather strop, bit sometimes i still feel a burr. Have tried pulling the edge through soft wood even, still feel a burr there. Is the burr im creating too heavy?
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The burr should be folding over from side to side at every stage and if it’s not your not getting both sides to apex and may not be reducing the size of the burr. So when it forms on one side at your course grit and you switch sides you should feel the burr switch sides. You can remove the burr by cutting through a few pieces of cardboard before going to the finer grit and you should feel the burr with the fine grit too. Also make sure to use some honing compound on your strop as that well really help polish and remove the wire edge.
 
Also I’ve sharpened rough axes and test choppers with a 60 grit belt and was able to pull the burr off with a strop with compound and was able to shave arm and leg hair it just takes a minute and you need to go back and forth from one side to the next and not just 10 passes on one side then 10 on the other
 
As has been brought out already grit size doesn't have anything to do with being able to hit the apex of the edge. I know it sounded weird to me when I switched to course edge sharpening because everything I had learned about sharpening before that said that I had to refine the edge to get it to shave. All that is needed to shave arm hair is to hit the apex and then strop. I prefer a firm strop for this so I don't round the edge over like what happens when using a leather strop if you aren't careful. Once you have it down sharpening isn't much of a challenge and can usually be taken from dull to shaving in 2 minutes. This is a very different edge than is used on a razor. A true razor edge isn't very useful for anything other than shaving. Thickness behind the edge is important for cutting but it doesn't have a lot to do with shaving arm hair. It is easy enough to make a axe shave and even a ice skate would probably be able to shave hair.

If you are having a hard time removing the burr try switching to a finer grit and do some very light stokes at a increased angle. This should help the burr come off and will give a micro bevel. If using softer steels burr removal can be tough. Pulling the edge through a cork or softwood can also help to strip it off. Once you have that burr you just have to find a way to strip it off without damaging your edge and you have a knife that will shave.
 
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