Knife sharpening techniques for all

[Ranger Psych]

Personally, I packed my Gatco system and a leather belt in my D bag and just had a single 4" long medium grit stone circa what comes with the (still?) issued USAF Survival knife in my shave kit in the ruck. The one that comes with the survival knife is adequate for most purposes. I personally would venture that all the multi-angle stuff is more for "proper" maintenance, both preventative and remedial, on edges.

Especially with how we roll now, you'll see that D-bag before you outrun the edge on your knife if you're not a meathead that sticks knives in the ground etc. Given the time, you can still do a good job with a medium grit stone plus a riggers belt as a strop, considering that while it's of variable grit your belt will collect dust and crap that functions as a cutting media on your impromptu strop.

 

[Barbarian]

Okay... lifting agents.... I believe in them, I tend to use food grade mineral oil, but have been known under advisement by Wayne Goddard, Bill Harsey, Ken Onion, Ken Brock, Gary Melton (who admits he is not great at sharpening), Gene Lake, and others (Yeah, I've been to a few too many knife shows for most people):
Simple Green
WD40
Used Motor Oil
Olive Oil
Vegetable oil
melted Crisco
Specialty honing oils of various flavors/manufacturers

As you can see it's basically dealer's choice... something that will lift and suspend the cut steel is what is important.

NEVER use anything but water on a Japanese water stone, ever... except when cleaning... a tiny amount of mild detergent, and possibly a nagura stone to even the face. I do store my Japanese water stone in water with a little bit of tincture of green soap to inhibit any microbial growth so it is always ready for use.

Just a note. If you search for mineral oil online, you'll get many more results if you search for "pharmacopeia grade" mineral oil instead of "food grade". I prefer mineral oil as well. It's cheap and works as well as anything. Though chemicals in it can cause your babys to be born nekkid.

 

[Ranger Psych]

It also makes interesting computer builds if you want to get really funky with things.

 

[compforce]

Just a note. If you search for mineral oil online, you'll get many more results if you search for "pharmacopeia grade" mineral oil instead of "food grade". I prefer mineral oil as well. It's cheap and works as well as anything. Though chemicals in it can cause your babys to be born nekkid.

Disclaimer: I don't use a utility knife very often any more. Usually it's just my leatherman to open boxes and such. My main sharpening efforts are kitchen knives now. I have some very high quality asian knives so I take really good care of them. (Asymmetrical V and Semi-convex)

Let me make it easy for you on the mineral oil side... This is what I use. http://smile.amazon.com/gp/product/B0017ID92K/ One bottle for my tristone. Everything else is water based. This oil can also be used on wooden cutting boards safely.

Here are my stones:

http://smile.amazon.com/gp/product/B0001MSA72/ Tristone
http://smile.amazon.com/gp/product/B000H6JDFA/ Water stone (1000 grit)
http://smile.amazon.com/gp/product/B000H6FSGI/ Water stone (4000 grit)
http://smile.amazon.com/gp/product/B000H6JDFU/ Water stone (8000 grit)
http://smile.amazon.com/gp/product/B0000DD21Y/ Stone holder

I use the tristone for rough/chipped edges and restoring if a knife drops and breaks the point
1000 for a knife that hasn't been sharpened in a long time
4000 is normally where I start since I don't let my knives get too bad before I resharpen. Once a month at the longest
8000 is the final polish on mine. I don't strop them, just use the really fine stone.
The water stones come with a case that will work as a base, but I like having a firm anchor that won't slip

I also have some kitchen specific stuff that you don't really need for other types of knives.
Diamond sharpening rod (flat)
Diamond sharpening rod (round)
Honing rod

 

[x SF med]

@compforce - we're going to wait on semi-convex techniques, they require lots of practice and a 'feel' for the shape that takes a very skilled hand to get right, especially on fine taper blades like a kitchen knife, or a sword/saber.

You do bring up a very good point about the tools for sharpening fitting the job for the blade - a field/utility/work blade does not usually require the polish that a kitchen knife does - the biggest exception being fine woodworking tools.

You also bring us to the next point of thought - edge angles. the steeper the angle the more chance to chip, dull, or mar the edge. convex or semi-convex grinds mitigate this by using the power of the arc/arch to add strength to the edge, but are MUCH harder to get right. Next in strength is a stepped or complex/multibevel where your actual edge has 2 or more angles per side (exclusive of the drop from the spine, or primary angle. the attachment is not great, but I'm not a paint expert, it'll give you an idea of a standard geometry:

 

[compforce]

@compforce - we're going to wait on semi-convex techniques, they require lots of practice and a 'feel' for the shape that takes a very skilled hand to get right, especially on fine taper blades like a kitchen knife, or a sword/saber.

You do bring up a very good point about the tools for sharpening fitting the job for the blade - a field/utility/work blade does not usually require the polish that a kitchen knife does - the biggest exception being fine woodworking tools.

You also bring us to the next point of thought - edge angles. the steeper the angle the more chance to chip, dull, or mar the edge. convex or semi-convex grinds mitigate this by using the power of the arc/arch to add strength to the edge, but are MUCH harder to get right. Next in strength is a stepped or complex/multibevel where your actual edge has 2 or more angles per side (exclusive of the drop from the spine, or primary angle. the attachment is not great, but I'm not a paint expert, it'll give you an idea of a standard geometry:
View attachment 13272

yup, just wanted to get the links out there for folks. Wasn't trying to jump into your lesson plan, just links to the equipment. Heck, I didn't even mention that my knives are CroMoVa steel (which is too hard for most basic stones, thus the diamond sharpening/honing rods and high quality industrial water stones). But that's a discussion for much later...

 

[compforce]

OK, so here is a real picture of a double bevelled knife. I put red lines so everyone can see where the two bevels are located. Technically this one is double bevelled asymmetric semi-convex edge, which is why the bevels photograph so clearly.



Pop quiz. this is an edge-on view of a knife held up to a flourescent light. What is the shape of the edge on it? (for those that are learning, not you Troll). Please be specific. The grey fuzzy thing at the top is the actual cutting edge, which is too fine for the camera's resolution.





























To keep the thread from devolving, here's the answer: It's an asymmetric double bevelled V. The first bevel is clear in the pic, the second bevel is only on the edge on the left of the pic where the cutting edge starts, right where it starts to fuzz out. This is a right-handed asian style chef's knife. The final bevel is 60 degrees on the picture's left and single bevelled 30 degrees on the right.

 

[x SF med]

@Ooh-Rah - you asked about sharpening a Tanto style blade. Treat each cutting edge as a separate knife, start with the slicing edge, then sharpen the thrusting edge. Be careful... you have to keep the angles right and not slice off digits as you work.

I just sharpened a buddy's Tanto bladed folder tonight, and then while I was a it, touched up the little Boker and the Sebenza. Be careful lending knives once you get addicted to keeping them sharp, people are idiots and expect to be handed a butterknife, not a straight razor when they borrow your pocket knife. Hand them a 1.5" properly sharpened tool and they end up in the ER getting stitches, spouting about "I didn't think a little knife would be that sharp..." to which I usually answer, "What the fuck do you think a scalpel is, idiot? It's a very sharp little knife, right?"

Which leads us to..... initial inspection of a blade prior to sharpening.

And.... where do we start with the inspection? Anybody? What tools do you think are needed?

 

[Ooh-Rah]

And.... where do we start with the inspection? Anybody? What tools do you think are needed?

Sigh...I answer only to communicate the level of incompetence you are dealing with. (but I'm reading and learning )

My current level of inspection is pulling my thumb across the blade for resistance, seeing if it will drag across my finger nail, and determining if I get resistance trying to slice thru a gas receipt. Based on what I've read so far, I would imagine a magnifying glass would come into play somewhere. For what? Again, talking out of ignorance, but I would think you'd use the glass to inspect the blade for any dings/dents that may need special attention paid to it.

 

[CDG]

I've also always used the shave a fingernail or slice a piece of paper test for sharpness.

 

[Barbarian]

Sigh...I answer only to communicate the level of incompetence you are dealing with. (but I'm reading and learning )

My current level of inspection is pulling my thumb across the blade for resistance, seeing if it will drag across my finger nail, and determining if I get resistance trying to slice thru a gas receipt. Based on what I've read so far, I would imagine a magnifying glass would come into play somewhere. For what? Again, talking out of ignorance, but I would think you'd use the glass to inspect the blade for any dings/dents that may need special attention paid to it.

Glass is especially helpful for identifying any leftover burrs , any deformities at the very tip of the edge, or any area that has been missed by the stones due to wobbly hands. Any of these will cause the edge not to cut as well as it can.

 

[x SF med]

Actually the first piece of equipment you need is your eyeballs.

Is there any rust, are there any huge dings in the blade, is the blade itself straight and true (every blade has a very slight bend to it, but if it's discernible to the naked eye there is something wrong).

Hold the handle of the knife (fixed or folder) just below and in front of your dominant eye, with the blade pointing away from you, at a light. line up the knife so you are looking right down the cutting edge. do you see any shiny spots along the actual hairline edge (should be blurry because it's sharp) of the cutting surface? Those are flat spots, missed areas from sharpening or damage from use/normal wear. are the sides of the edge consistent with the type of grind. follow the cutting edge by rolling the knife the same way the blade geometry is made and do this inspection from ricasso/base to tip.

Now, get out your magnifying device and do the same thing, you will really see the micro-serrations of the matrix/aggregate structure of the steel if you use a 15x magnifier (I use a jeweler's loupe) and the flat spots/dings. Pay special attention to the 'wall' geometry leading up to the cutting edge, are they even in depth, angle and smoothness? These let you know if the knife is going to need special attention anywhere. Can you see a wire edge, or does the edge look 'bent' to one side? we can fix that later, but know it's there.

A fine grease pencil to mark areas that need attention, or just a pencil/fine sharpie, is really helpful.

NOW, is the handle loose - fixed or folder, this is important, are the scales handle wrap tight, is there a large amount of dust or grit in a folder's action, is there dirt in the sheath. Generally, is the knife in good shape?

Take a break, have a drink of water.... and get the next knife out and start over.

 

[Mac_NZ]

My blades, the Victorinon multi tool (not pictured) gets the most work. The Buck/Strider is a breeze to sharpen, the GB I'm still not happy with the edge after owning it for 8 years, S30V is the devil and the only reason I own diamond stones now.

 

[x SF med]

You need to use more pressure while sharpening with harder and smaller grain steels.

One of the biggest errors people make, is too light a touch while sharpening... you are removing hardened steel, it takes force.

 

[Barbarian]

View attachment 13280 My blades, the Victorinon multi tool (not pictured) gets the most work. The Buck/Strider is a breeze to sharpen, the GB I'm still not happy with the edge after owning it for 8 years, S30V is the devil and the only reason I own diamond stones now.

You need to use more pressure while sharpening with harder and smaller grain steels.

One of the biggest errors people make, is too light a touch while sharpening... you are removing hardened steel, it takes force.

Excellent posts, Gents. This is an important point. It's important in practice, but also because you won't find it written anywhere, for whatever reason, so I want to emphasize this:

The amount of pressure required for sharpening varies, depending on the material of the blade, as well as the material of the stone.

 

[x SF med]

Always take a look at a new blade of the design you are sharpening, part of the cutting design is the primary bevel to the cutting bevel, after repeated sharpening (years of heavy use/sharpening) you may have to take down the primary bevel as your first step of sharpening. Anybody want to guess why?

 

[Barbarian]

Always take a look at a new blade of the design you are sharpening, part of the cutting design is the primary bevel to the cutting bevel, after repeated sharpening (years of heavy use/sharpening) you may have to take down the primary bevel as your first step of sharpening. Anybody want to guess why?

Nobody gonna swing at this one? @Ooh-Rah?

 

[Ooh-Rah]

@Barbarian and @x SF med , again, I answer only to participate and demonstrate my lack of knowlege, but reenforce my desire to learn. I would think the reason you need to take down a much used bevel is that it has been sharpened so many times, that the origional and designed angle is no longer obtainable. My follow up question to that woud be, can you get to a point where you are actually shaving off noticeable blade in the desire to get the original bevel back?

 

[x SF med]

My follow up question to that woud be, can you get to a point where you are actually shaving off noticeable blade in the desire to get the original bevel back?

Yes.

 

[Barbarian]

Attached is a group of diagrams which show three cross sections of a blade. Diagram A shows a blade in new condition.

Diagram B shows the cross section of a blade that has seen years of hard work and sharpening without addressing the blade's primary bevels. As you can see, the area where the primary, and secondary bevels meet is pretty thick.

The final diagram displays a blade which has endured years of use, just like the blade in diagram B, except that the primary bevel has been worked, as @x SF med suggested, until the blade has reached its original cutting geometry.