Sharpening knives

[Squisher]

Yes, because knives and dies are exactly the same.

Yes they are. They are cutting edges. Most dies cut by a scissoring action, but cutting is cutting. In each case the angles of the cutting edge are a trade off between ease of cut and longevity of the edge. When you polish a cutting edge, like you said, you make it convex and more prone to dulling.

 

[moonbogg]

I have used three and they are all amazing.

Jet Slow Speed Wet Sharpener

Edge Pro Apex

Spyderco Sharpmaker.

The Sypderco can be hard to use for putting a new edge on knives, but its great for maintaining an edge or if the knife doesn't need a whole new bevel. Those stones take a while to reform a bevel. The other two are amazing. I use the apex almost exclusively, but the Jet will put a razor edge on anything is short order.

EDIT: Just FYI, I used the Jet to put a large, new bevel on knives and then use the spyderco for the micro bevel and subsequent touch ups. This combo works really well as long as I use the spyderco for all future touch ups until rebevel is needed. switching sharpeners will force you to rebevel the edge, so try to stick with one sharpener or technique as a general rule or else you will be constantly rebeveling and taking off a lot of steel.

 

[xSauronx]

I have a Spyderco Sharp Maker and it works great. I'm not interested in trying to free hand sharpen a blade and get it ultra super sharp, just damn sharp and easily and quickly, which the Sharp Maker does. Maybe some day I'll try stones.

I've also heard the Edge Pro Apex is great (similar type of thing).

another vote for the spyderco. stupid easy to use and works great.

i have a water stone i use a couple of things, but the spyderco is fantastic.

 

[Howard]

Yes they are. They are cutting edges. Most dies cut by a scissoring action, but cutting is cutting. In each case the angles of the cutting edge are a trade off between ease of cut and longevity of the edge. When you polish a cutting edge, like you said, you make it convex and more prone to dulling.

I don't profess to understand the science of die geometry but I understand very well that a convex edge can cut extremely well and anyone would be hard-pressed to prove that an excellent convex edge is inferior to an excellent double-bevel, saber-ground, flat-ground, etc. edge in any sharpness test* or edge retention test, given approximately equal sharpening angles.

By the way, going back to your original post, a sanding belt can create a fairly straight grind (for most purposes) as long as you have a rigid plate backing it.

*I say sharpness test and not cutting test because cutting performance depends on more than just edge sharpness

 

[shortylickens]

To be pedantic, the steel raises the burrs. It's meant to straighten an edge that's been folded over through use.

Quite true good sir.

Carry on.

 

[Squisher]

I don't profess to understand the science of die geometry but I understand very well that a convex edge can cut extremely well and anyone would be hard-pressed to prove that an excellent convex edge is inferior to an excellent double-bevel, saber-ground, flat-ground, etc. edge in any sharpness test* or edge retention test, given approximately equal sharpening angles.

By the way, going back to your original post, a sanding belt can create a fairly straight grind (for most purposes) as long as you have a rigid plate backing it.

*I say sharpness test and not cutting test because cutting performance depends on more than just edge sharpness

Believe me those tests have been done and done since the beginning of the industrial revolution. Everyone for a couple hundred years was looking for an edge (<--pun) over the other guy. Being able to cut faster with less break down of cutting tools is what everyone wants. Most of the movies they start showing you in your apprenticeship that involve cutting techniques are grainy black and white ones from the '30s. What holds back sanding belts is both the softness of the belt and the tendency to wrap around the object you are sanding. I realize both of these are not easily seen by the naked eye especially at speed.

 

[Raduque]

We have one of these at work. http://www.amazon.com/Update-Interna...arpening+stone

It works pretty good if you get the angle right.

 

[kage69]

As I said before, I use a belt sander to get me an edge that can split hairs lengthwise. Depending on how worn the knife is, I may be able to accomplish that in under 10 minutes.

And you're probably taking off more steel than necessary. It's not impossible to get a sharp instrument using a belt sander, I just happen to prefer methods that don't generate as much heat.

 

[Cerb]

So, what makes a non-convex edge so much better at handling being smacked into the cutting board, and then torqued or scraped a little?

Food is soft. The angle when cutting is very much imprecise to due to human error. A soft steel with a thin bevel will roll easier. A hard steel with a thin bevel will chip easier. A convex or multi-bevel edge strikes a balance between thinness and angle, since much of the force you are using to cut with is due to the part of the blade in contact with already-cut food. A shallower angle reduces the downward pressure you will need as you cut, while a steeper angle will be more resistant to rolling, chipping, or thickening.

By striking a balance between them you can minimize the needed force to cut the food, which will also minimize the pressure that the edge receives from the cutting board.

Die-cutting I would think assumes that you are cutting a material that itself can significantly wear out a blade, that you are not slamming that blade's edge into a hard surface at the end, and that you are dealing with edges that remain aligned to one another and their respective surfaces, and that you are often sheering against a surface normal to the blade's edge. None of those things hold true for a kitchen knife.

 

[Gillbot]

I use a set of steels

http://en.wikipedia.org/wiki/Butcher_steel

 

[onza]

Lansky user - works great and affordable.

 

[Howard]

And you're probably taking off more steel than necessary. It's not impossible to get a sharp instrument using a belt sander, I just happen to prefer methods that don't generate as much heat.

I don't know if you are randomly throwing arguments out there but it seems as though you have never seen someone properly sharpen with a belt sander.

1) I check the edge often for the formation of a burr. I go up to the next grit as soon as the burr is ready. This happens at the same stage whether the knife is being sharpened manually or with a power tool.
2) Heat is not an issue given that frequent stopping is made to check for burr. For heavy stock removal the edge is simply dipped into cold water. I have never gotten an edge so hot I could not touch it*; ergo, the heat-affected zone is so small as to be readily eliminated with the any of the finer grits.
3) The generation of heat is roughly proportional to the rate of metal removal. You can take your time sharpening worn knives but I find I don't care to sharpen as much as I used to.

*Except on one paring knife I did once. You have to be careful with small, sharp points.

 

[Howard]

Believe me those tests have been done and done since the beginning of the industrial revolution. Everyone for a couple hundred years was looking for an edge (<--pun) over the other guy. Being able to cut faster with less break down of cutting tools is what everyone wants. Most of the movies they start showing you in your apprenticeship that involve cutting techniques are grainy black and white ones from the '30s.

Are you still talking about punches or are you talking about kitchen and utility knives?

Seriously, why is there an equivalency between the two? Edge geometry of punches are not relevant to this discussion unless you can prove that what is good for a punch edge is equally as good for a knife edge.

What holds back sanding belts is both the softness of the belt and the tendency to wrap around the object you are sanding. I realize both of these are not easily seen by the naked eye especially at speed.

So you're saying that sharpening a knife with sanding belts cannot give you edges that are perfect for that knife's application?

 

[Howard]

Believe me those tests have been done and done since the beginning of the industrial revolution. Everyone for a couple hundred years was looking for an edge (<--pun) over the other guy. Being able to cut faster with less break down of cutting tools is what everyone wants. Most of the movies they start showing you in your apprenticeship that involve cutting techniques are grainy black and white ones from the '30s. What holds back sanding belts is both the softness of the belt and the tendency to wrap around the object you are sanding. I realize both of these are not easily seen by the naked eye especially at speed.

By the way, the post you were quoting was definitely not in the context of industrial dies.

 

[jcwagers]

While I've never used one, the Work Sharp seems to be well-liked by a lot of people for sharpening all kinds of things.

http://www.amazon.com/Work-Sharp-WSK.../dp/B003IT5F14

 

[ManBearPig]

deleted

 

[Cerb]

Jeez, sharpening knives is costlier than I thought lol.

With sandpaper and mouse pad, you can be working on it for <$15, and fuel might not be an insignificant part of the cost.

Norton synth combo India stones can be had for <$30, <=$50 with a box/holder, and you can use mineral oil from the pharmacy, to alleviate any chemical worries. They won't work very well on harder steel, like is common in Asian knives, but most European or American knives they're great for.

Spyderco's Sharpmaker is $54 at Amazon, and at most, you might want one more finer rod. I see no reason why such a system should not last a lifetime, and unlike the Lanksy type, works for large blades, too.

Carbide metal removers can be had for $5-20.

It can get as expensive as you want it to get .

 

[Squisher]

By the way, the post you were quoting was definitely not in the context of industrial dies.

No, I kinda veered off into cutting tools which are closer to the application of knives, but never the less use the same principles as any die based cutting. It is all the same with each being optimized for its use. People have been sharpening cutting tools for use on lathes, mills, shapers, etc., cutting all types of materials, and verifying the results for a long time. It doesn't matter whether you are shaving off your beard with a razor, peeling off a wood chip on a lathe or punching a hole in a piece of sheet metal, in each case the same cutting principles are used with each being optimized and none use a convex geometry.

 

[stargazr]

No, I kinda veered off into cutting tools which are closer to the application of knives, but never the less use the same principles as any die based cutting. It is all the same with each being optimized for its use. People have been sharpening cutting tools for use on lathes, mills, shapers, etc., cutting all types of materials, and verifying the results for a long time. It doesn't matter whether you are shaving off your beard with a razor, peeling off a wood chip on a lathe or punching a hole in a piece of sheet metal, in each case the same cutting principles are used with each being optimized and none use a convex geometry.

As a tool & diemaker I agree with this. However, I think if you were careful to maintain the correct angle, and control the heat so as to not affect the hardness of the steel you could get an acceptable edge on a belt sander that would cut. Generally if the belt is very course the edge will be more rounded; a finer grit belt will give you more of a true flat edge but will heat up faster so you will need to have some water to quench it so as not to lose the temper. Personally, I would never use this approach, especially on a good knife. All I'm saying is you can make a sharp edge, but if you are inexperienced you can easily ruin the knife.

The thing is that people tend to prolong sharpening too long, to the degree that the point is so worn down, the original beveled edges need to be re-established. There are various tools for accomplishing this. The difficulty in using stones free hand is maintaining the correct angle. Plus you need to start with something more course that an Arkansas set. Like an India stone. Then finish with the Arkansas stone set.

IMO, this is how many people ruin the original factory edges. You need something to actually remove a bit of metal to get that shape back, not polish it. They use too fine a stone and also fail to keep the original angle. So what you end up with is, if you look at it under magnification, a kind of convex shape made up of many different flats or angles as opposed to a nice, flat bevel. This kind of edge will not cut well.

 

[jaedaliu]

I use synthetic japanese waterstones. Watched a couple of youtube videos on it & away I went. All my kitchen knives are sharp as razors. I am a professional chef & the time & skill to do this myself has paid for itself.

Interesting. Knife maintenance wasn't part of culinary school? I assumed that the whole "your knife is an extension of the body" approach would have included instruction on which knifes to use and how to take care of them.

 

[xaeniac]

get the edgepro apex

 

[shortylickens]

With sandpaper and mouse pad, you can be working on it for <$15, and fuel might not be an insignificant part of the cost.

Norton synth combo India stones can be had for <$30, <=$50 with a box/holder, and you can use mineral oil from the pharmacy, to alleviate any chemical worries. They won't work very well on harder steel, like is common in Asian knives, but most European or American knives they're great for.

Spyderco's Sharpmaker is $54 at Amazon, and at most, you might want one more finer rod. I see no reason why such a system should not last a lifetime, and unlike the Lanksy type, works for large blades, too.

Carbide metal removers can be had for $5-20.

It can get as expensive as you want it to get .

Yeah in cub scouts we used the wooden block with sandpaper and it was actually not horrible. But generally speaking I want a real sharpener.

 

[Howard]

No, I kinda veered off into cutting tools which are closer to the application of knives, but never the less use the same principles as any die based cutting. It is all the same with each being optimized for its use. People have been sharpening cutting tools for use on lathes, mills, shapers, etc., cutting all types of materials, and verifying the results for a long time. It doesn't matter whether you are shaving off your beard with a razor, peeling off a wood chip on a lathe or punching a hole in a piece of sheet metal, in each case the same cutting principles are used with each being optimized and none use a convex geometry.

But it wouldn't make sense to use a convex edge on a lathe bit or a punch. It can make sense to use a convex edge on a knife. Why can't you accept this?

 

[ManBearPig]

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