Instagram for Craftsmen

Instagram is often unthought of or overlooked by craftsmen, but is very proficient at getting your name and work out there and in common knowledge. The biggest two pluses for craftsmen are these: one, that it operates primarily on photos, and two, it’s incredibly easy to immediately upload photos from your phone and post them. This means you can take and upload pictures as you work on a project, without slowing down your work. And so, followers pretty much see the entire process from start to finish, so they get the inside scoop on both how much work it is, and how the object (in my case knives) is really built. People are interested in learning how things work, and so seeing the steel being forged, seeing the blade being ground, sanded, sharpened, the wood cut and formed, and so on really draws them in, and they can see, through the process of its making, exactly what the quality is. They can also see when a new knife is finished, and can make an offer on it. When this happens, and they get the knife, they will post a photo of it to their followers, which increases my following. From one sale to a knife enthusiast, fifty of his followers followed me, and many of those gave offers on my knives.

Also, many other types of craftsmen, with related trades, can interact with you. For example, I follow a lot of leather workers and woodworkers, and a lot of both follow me. The trades overlap, so everyone has at least a basic understanding of how the other craft works, as well as a use for it. Leather workers and woodworkers both have a need for good custom knives, and knifemakers need leather sheaths and handle woods. Perfectly set up for trades, and once a trade is made, both people post photos of what they got, and so both get a follower increase.

How I make a Knife, Pt. 4

Once the epoxy had cured, I clipped off as much of the protruding pin as I could with wire cutters then used the belt grinder to grind it flush with the wood.

I then wrapped the entire knife tightly with Saran wrap, and wrapped electrical around that to hold it in place. This was to keep the knife from getting wet.

The Saran wrap and tape keeps the blade from getting wet, which could ruin the wood at this stage

I took the leather and soaked it in water, making sure it was thoroughly wet inside and out. Leather is interesting that when dry, retains it’s shape, but when wet, becomes malleable and easily formable. I folded the leather over the knife, which due to the Saran wrap kept dry, and pressed the leather over the blade and the front of the handle using several wood boards and clamps.

The boards press the leather down on the blade, and due to the angle pinch the excess around the handle together to form a snug cocoon.

I left it to dry overnight. This type of sheath not only covers the blade, but part of the handle as well, so the knife stays securely in the sheath with active movement, yet is easy to remove when you want it.

The next day, I removed the knife from the sheath and took of the Saran wrap, and put some tape around the bolster to protect it, and began hand sanding the handle. The tape kept the sandpaper from marking the bolster should I accidentally touch it.

The tape protects the bolster from sandpaper

I put the blade in the vise, using wooden jaws so as not to mark it, and sanded the blade well, starting with 320 grit and moving up to 1500. When sanding the blade, I use a flat stick so I can get flat and even pressure, but for the handle I use my fingers, which one must note are perfect for the job, as the handle has many curves and is round. After sanding the blade to 320, I wiped the blade in a diluted cedarwood oil mix, cleaned it off, sanded to 400, wiped again, and so on. This is so I can well saturate the surface of the wood without drenching it; on many woods if I wait until I get to 1500,  the oil doesn’t sink in using the sandpaper scratches.

Once I was done sanding, I placed a few bits of beeswax on the handle and used a heat gun to melt them over the blade, and then used scrap leather to rub it in, both sealing the wood and simultaneously polishing it.

Now the beauty of the wood is shown

With the knife completely finished save for sharpening, I returned again to the sheath.  I used the slack section of the belt grinder to grind flush the edges.

I used the grinder to perfectly true up the edges

With the edges of the leather true, I opened the sheath up, placed in the knife, and used a pencil to make a guideline along the edge of the blade onto the leather. I then dabbed in a generous amount of epoxy on the outside of this line, from throat (where the blade enters the sheath) to tip.

I make sure not to go over the line, as that is where the blade will be

I then used a number of bricks to press the edges together, and waited for it to dry. While I waited, I began preparing the rivets for the sheath. Leather sheaths are generally held by rivets or by thread, and as I did not have the right thread and also quite bad skills at sewing, I went with rivets. I cut off a long section of copper wire, and placed it end up in the clamp, about half a centimeter protruding, using one wooden jaw and one steel jaw. The wood jaw squished around the wire, holding it on all sides, so it would be less likely to bend over one way or another. I used the back of a ball peen hammer, and lightly began tapping, using the weight of the hammer rather than exerting any force myself. A mis-strike bends the wire over, sometimes too much, so I have to clip the end off and start again. Using the convex side of the hammer mushrooms the copper out, into a nail head shape.

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I then clip off the excess wire, so the rod of the “nail” is a little more than a centimeter long. Epoxy hardens relatively quickly, so by the time I was done with the six rivets, it had cured. I drilled holes in possible stress points in the leather, at the tip, top of each side, and evenly in between. I put a rivet into a hole, and the sheath on the vise anvil, rivet head up. Then I used the same technique as I had earlier, (called peening) to mushroom the ends of the rivets into flat heads, firmly holding both sides of leather together. This video shows the full work of the peening. https://instagram.com/p/0mDFLzkPW1/

Once all the rivets were in place and peened, I used a leather conditioner to clean and color the leather.

Then for the final step, I began sharpening. First step in sharpening is always establishing the edge, grinding down both sides until they meet. All knives have two bevels, the secondary bevel, which stretches from or nearly from the spine, until almost to the cutting edge. The primary bevel goes from the end of the secondary bevel to the very edge of the knife, the part that makes first contact when cutting.

In the far right diagram, the primary bevel are the two slopes that start at the point, and go until a corner. The secondary bevel is corner where the primary bevel ends, and extends back until the spine of the knife. In an almost completed but not yet sharpened knife, there is the secondary bevel, but no primary bevel, it’s just a flat surface

In establishing the edge, I’m making the two edges meet in the center, using a coarse stone, so I use a vigorous back and forth motion, shown here. https://instagram.com/p/0mFLtPkPaX/

Establishing the bevel is just making the two sides meet and eliminating the surface that is 90 degrees to the blade. I always sharpen with the knife raised above the stone at about 20 degrees, or less if I can. Once the bevel is established, I hone the blade, making sure there is a very sharp and exact corner. This is by single motions, drawing the blade from tip to heel (end of the cutting edge) five times, running the edge along wood to knock off any tiny bits of steel (burrs) left on the edge, then flipping the blade over and drawing the blade from tip to heel five more times, and de-burr it again. Then I switch to a finer stone and repeat. The trick to making the blade razor sharp (literally), is keeping the blade at the same angle throughout, so the edge is not rounded over. It’s a lot harder than it sounds.

After a quick cleaning, the knife is now completed.

Finis!

 

How I make a Knife, Pt. 3

A good knife needs to be able to be sharp, to not dull after little use, and to not break under pressure. By using heating and cooling methods, I can manipulate the physical properties of the steel to meet these standards. First what I need to do, is harden the steel, so it can be used many times without dulling. To do this, I heated up the blade in the forge until it was a cherry red, the point at which steel, when touched against a magnet, does not stick. Once the entire blade was up to this temperature, I plunged, or quenched, the blade in motor oil. https://instagram.com/p/0eOm8jkPUs/

When the blade is heated to that temperature, the iron atoms switch formation from small closed cube formations to larger open cube formations, allow carbon atoms, which had been floating around between the cubes, to float /inside/ the cubes. When the blade is shock cooled in the oil, the cubes shrink and close up too quickly for the carbon to float out, trapping the atoms inside the cubes. This makes the steel very rigid and hard, very hard to dull, but very brittle as well. To toughen the steel, I needed to heat the blade to around 400 degrees, which I did with the kitchen oven. This opens the cubes up a tiny bit, allowing a few carbon atoms to escape, lessening the pressure and making the blade much tougher, while still retaining it’s ability to hold an edge, that is, not dull.

The freshly quenched blade. At this point, I could break the blade with a few fingers

The process of heating the blade in the oven to toughen it is called tempering. I left it in the oven for three or four hours, giving the blade time to fully get to even heat, inside and out. The temperature at which I temper is determined by the amount of carbon in the blade, most files and rasps, like this one, having about .90% carbon by weight. While the blade tempered, I began working on the sheath. I first cut out the leather in the the shape I wanted, which I would later fold in half, using a paper cutout model as a size reference.

The leather will later be folded in half

I then use a metal stamp to make a decoration along the edge, quite easy to do as leather takes stamping very nicely.

I will later true up the edges of the leather

I set aside the leather for now, as the next step in sheathmaking requires the nearly finished knife.

After the blade finished tempering, I cooled it and roughly sanded away some of the black scale on a 220 belt. I then assembled the knife and used a cobalt alloy drill bit to drill through the handle and tang.

I took out the blade and put it in the clamp, bevel up, and began hand sanding. This is the most tedious and boring and taxing part of all of bladesmithing. I start with 220 grit sandpaper and work upwards, to 600, using a piece of wood for even pressure.

This can sometimes take hours to sand a knife, I’m not sure exactly how long as I tend to not be able to sense time well when bladesmithing. The worst part is taking out the small scratches left by the grinding belt, as they can be very deep and I’m removing all the steel within an inch radius with sandpaper to grind down even to the depth of that scratch. Anything I don’t get with the very first grit of sandpaper I can’t get out later.

Every one of these scratches has to be sanded out, it can sometimes take up to fifteen minutes just to take out one scratch. It helps if they are all in one area

Finally, I finished sanding, at 600 grit.

600 grit blade

I began to get ready for the final assembly of the blade. The pin material I had was a little too thick, so I had to grind it down to size. To get it evenly ground without any facets, I put the rod in the drill and ran it against the belt grinder, the rotations of the drill grinding the rod evenly on all sides, bringing it to perfect size for the hole.

As 36 is a very rough grit, it creates tiny ridges all around the pin, which will give the epoxy later a very good grip

I then mixed up the epoxy (using the pin; it gets the pin nice and covered) and dabbed a generous amount into the handle cavity.

The tape roll at the bottom is just so I could hold up the handle, take a photo, and hold the pin all at the same time

I also slathered a little on top of the wood so there would be no space between bolster and wood, in case the drilling had been a millimeter off. I slid the bolster onto the tang and the tang into the handle, and after pressing together and making sure the blade was straight, inserted the pin.

Freshly epoxied knife

How I make a Knife Pt. 2

While the blade was normalizing, I went to work on the handle. I chose a piece of spalted maple I got from a trade a while back. Spalted maple is maple that has small lines of fungi running through it, discoloring the wood. The fungi has of course, died since the the wood was dried, leaving only the coloring. I cut off a block slightly longer than the width of my hand, drew a rough line over it for the handle shape, and cut it out.

Soon after taking this photo I recut it to a better shape.

I then took it to the belt grinder, using the slack section on a 36 grit belt, refining the shape and rounding and forming it.

Rough formed handle

I went for a “coke bottle” shape, which offers very good and comfortable grip, thinning around the forefinger and pinkie area, and thickening just outside those and in the palm.

The coke bottle shape gives a very nice grip

With the handle finished shaping, I began working on the blade, grinding the profile to how I like. I use the guidelines as only that, guidelines, permitting myself to grind extra here and there to improve it. I ground the false edge  (the little ridge on the back of the blade) first; my goal being the spine of the blade goes from the handle, hits the false edge, but subconsciously continues as the crease between bevel and false edge. The key to a good knife design is continuing and flowing lines throughout the knife.

I place the blade sideways in the clamp and grind with the angle grinder from above

I then begin grinding the bevels, using an angle grinder with a 120 grit flap disc. Most smiths would do it all on the belt grinder, but for me the angle grinder is faster, as I can bog down the belt grinder too easily due to a weak motor, which I need to upgrade. Here you can begin to see the design left by the rasp teeth.

The C-clamp on the blade is so I don’t grind too far and into the ricasso

I then grind around the ricasso and tang, and grind everything uniform on the belt grinder. Then I switched to a 220 belt on the grinder and sanded the blade. Because the blade was blackened, every scratch from the 36 grit belt showed up in black, so I knew exactly where I needed to grind.

I then began to bring the blade and handle together. I put the handle in the vise, blade side facing me, and drilled in a hole slightly longer than the length of the tang, and a little smaller in diameter. I then heated up the tang in the forge, and carefully pushed it into the hole. The heat burned away the wood directly in the way, smoking but not creating flame, as there was not enough oxygen inside the hole to start a fire. As the heat only burned away the wood directly in the way, and no more, the tang burned out a perfect fit for itself. At this point I also heated up the whole blade in the forge and normalized again, as the heat from grinding friction could create small stresses. The heat oxidized the blade and turned it black, which is handy for a reason I will explain in a minute.

Part of the design key is to always have the ricasso the same width as the immediately adjacent handle, creating a smooth transaction from handle to blade

I then began working on the bolster, which is a piece of metal between the handle and the blade, and acts as a transitioning piece. In this case I chose copper, as it is easy to work with and I have in plenty, besides being very beautiful when polished. I started with a thick (a little more than 1/4″ thick) sheet of copper, and cut out a square, and drilled it with a bit the same diameter as the thickness of the tang. I then used a round file to cut out the slot to the exact shape. I had to go slowly and carefully, just a little too big means a wobbly bolster, which I would have to throw away should I mess up.

I push with my right hand and put the palm of my left hand on the other end, to put pressure down on the copper

Every few seconds, I try to fit the tang inside, and note where it needs to be filed away more. Eventually I got a perfect fit.

Temporarily assembled knife

I used a miter saw to cut off the excess copper, then reassembled the knife and traced around the handle with a sharpie, and used an angle grinder to rough shape around that line.

Rough shaped bolster

I then finished it up to exact shape on the belt grinder.

Then it was a lot of sandpaper, until the bolster was 1500 grit, and used a polishing wheel on a dremel to polish the bolster.

Polishing the bolster, on a high speed dremel

With the bolster polished, it was time for heat treatment.

How I make a Knife Pt. 1

This is a detailed step by step overview of how I make a knife, in this case a field knife bowie style.

I began with the steel, a farrier’s rasp that had over time become too dull for use, which I picked up for free from a farrier. Files and rasps are generally high carbon steel, which means I can heat treat it to make a very good knife that will not break or dull easily. I broke the rasp in two, and used the bottom half which already had a tang. I began forging (forming it with the hammer and anvil), thinning and lengthening out, by beating on the rasp, edge up on the anvil. I heated it up in my forge (which I built ago with a torch, a paint can, insulator and clay) until it was orange hot, then forged until it was nearly black, at which point I would put back in the forge and repeat.

The rasp as it was begun to be drawn out (thinned and lengthened)

I would hammer for a while on the edge, then put the steel flat on the anvil, face up, to flatten it and keep from folding over. As I went along, I would heat up the steel until the whole thing was orange hot, then place one edge on the anvil and wait for a few seconds before forging. Steel acts as an excellent heat sink, and so the anvil sucked the heat out from the edge touching it, while the opposite edge remained almost unchanged. Once the edge touching the anvil was nearly black, I would then begin forging. Because the opposite edge was cold, it moved very little, while the hot edge would be pounded in and thickened. I’ll explain why I did this soon.

After a few heats (forging sessions) the blade was well lengthened out. Now what I needed to do, was forge the blade on its side so it would be evenly thick across the blade (my goal was a little more than a fourth of an inch thick). When I forged on the thicker area of the blade along one edge, the steel pushed out under the hammer blows, curving the blade forward.

The blade is a little more than a fourth of an inch thick across the entire piece. The straight side in this photo is what later will become the cutting edge, not the curved side

At this point I let the blade cool, then used a miter saw with a metal cutting blade to cut a slight slant, which you can see on the left side of the photo above. Now the reason I made the blade curved as shown, was to avoid a problem I normally reach at this point. When I normally forge the bevels (the bevel is the slant from the back of the knife into the cutting edge), I’m flattening the steel at an angle into a wedge shape. The steel being pushed away from the hammer has to go somewhere, so it expands sideways, which pushes the blade into a curve backwards, too much of a curve. However if I curve it forward first, which I did here, then when I forge in the bevels both the curves cancel out, and the blade straightens out. So what looks like the opposite of the cutting edge in the photo above, actually becomes the cutting edge.

So now I begin forging in the bevels, starting at the tip, working towards the tang, and back up to the tip.

The blade is flipped over in comparison with the previous photo

During all this time, I had been working with a 2.5 pound cross peen hammer, to get the heavy work done. At this point I switch to a lighter 1.5 pound ball peen hammer, to even everything out and do the detail work. I have to be very careful not to make any deep hammer marks, as they will be next to impossible to grind out later on. Once the bevel is about the thickness of two quarters, I begin to forge in the ricasso. The ricasso is the section of steel between where the cutting edge stops and the guard or handle begins. I don’t bother forging in too far, as it is quite easy to grind in later.

Cutting edge is the right side.

Then I forged in a decorative feature, similar to a gut-hook, just, well, without the gut-hook. I forged it in carefully and slowly, putting the blade at a 20 degree angle on the corner of the anvil, and striking with the hammer at a 20 degree angle to the blade. This pinched the back of the blade out just a little bit, which I will later refine on the grinder.

At this point forging was done. I straightened out the blade using light taps, then normalized the blade thrice. As a blade is heated, cooled, and forged, stresses form inside the steel. Heating the whole blade to the point at which it no longer sticks to a magnet (a reddish orange or so), and then letting air cool, takes out these stresses and makes the blade much less brittle. I then marked out on the blade where to grind using a sharpie. Most smiths use a sort of chalk, but I find sharpie ink works just fine.

Finished forged blade. Now for grinding.

First Lockback Folder

This was a fun project, one I tried just because I hadn’t done it yet, like making a RR spike knife or forging a tomahawk. I don’t plan on doing it again however, I prefer bowies. I started out as usual, sketching out the design, but this time doing a cutaway diagram. I based the locking mechanism off this one, basically called the “lockback” folder.

Photo credit: American Knife and Tool Institute

The construction is fairly simple, a lever in the back of the handle, the front of which pushes down like a puzzle piece into the knife blade. Only by pushing on the other end of the lever does it push up and out of the blade, allowing it to rotate.

I started with the blade, forging a 2 inch or so blade out of 1084, normalizing, and grinding. After I got  the blade to the shape I wanted, I flattened out copper, thin enough to minimize weight and look slim enough, but thick enough to be annealed and not deform easily, about twice the thickness of a dime. Using the blade as a guide, I re-sketched the folder in cutaway form, and cut the copper sheet to two dimensional shape (matching the yellow in the above diagram). After I had one piece cut out thus, I cut out a second one, clamped them together with a C-clamp and ground them flush on the belt grinder. Once this was done I marked where to drill the holes for each pin, and drilled them in. After deburring the holes I began working on the lever arm and the blade itself with files, matching the two so as to fit perfectly. From time to time I would compare it on one or the other copper frame pieces, using rods as temporary pins to make sure they worked and fit perfectly. Once I was confident it would work well, I cut out a back piece to give structure in the space between the frame pieces, and drilled it to fit accordingly. I constructed it slightly different from the diagram, using a torsion spring, with one arm between a pin and a back piece and the other arm pressing up against the rear lever arm. After test fitting it all, I began working on the scales, choosing two pieces of cocobolo that had a lighter streak running through them. I cut out the rough shape, placed under the copper frame pieces, and drilled in all the holes. Using these holes for temporary pins, I lined them all up and clamped them together, which I then ground flush on the belt grinder. Once this was done I unclamped them and shaped the scales individually. Looking back I realized I should have ground them thinner.

Finally, once I knew all the pieces fit together, I did the final assembly, placing down one scale, pins through each hole, epoxy on top of the scale, one copper frame on top of that, blade, lever arm, back piece, and spring on top of that, and another copper frame on top of those. I had to hold down the lever arm and spring pretty tight with one hand and sliding down the second copper frame above quickly to keep it from popping apart. Very stressful. After that I spread on some more epoxy, then the second scale on top, using a c-clamp to keep it all together.

Afterwards was the home stretch, clipping the pins and peening then grinding them flush, and sanding down the wood to a high grit and oiling, then finally sharpening. I had some complications with the spring, which required taking out a pin, replacing the spring, and putting the pin back in, which was very stressful and at time frustrating, but I got it all together. I’m happy with the result but not intent on trying it again, at least until I get more precise equipment.

Venturi Forge Burner

I really need to upgrade my forge burner, so I’m going to attempt this. This post is going to be more or less writing down everything I need for it, and how it works, so I can reference in the future. This type of burner focuses on the venturi principle, which states that funneling a pipe and reducing the diameter reduces the pressure on the gases flowing through, so whatever is being blown into that pipe sucks the nearby atmosphere into the pipe as well. So the basic venturi burner has a nozzle blowing the propane gas into a cone. This cone sucks the air outside in with it, mixing the propane and oxygen together as they flow. Increasing the gas pressure increases the air pressure roughly the same amount. At the other end of the pipe is where they both spread out and burn. Flame does not burn up inside the pipe because the force of gas and air pushes it out as it burns. This diagram shows the basic construction of a venturi burner. Most forges are quite large however so I’m not sure I’m going to want the standard 1 inch diameter pipe for it. What I need are:

Cone piece for the back, with holes drilled for a pipe to go through the side. http://www.acehardware.com/product/index.jsp?productId=29071566

Brass gas pipe section that goes through said cone, blocked off at the end. #57 hole drilled halfway in, pointing down the cone. Other end of gas pipe has converter to hose, which then attaches to a regulator, which screws onto gas tank.

Attaching to the small end of the cone, the long pipe, about a foot or so. This pipe will then insert directly into the forge. http://www.acehardware.com/product/index.jsp?productId=29375406

I’ll start the forge by putting a small piece of burning paper inside the forge and turn on the gas, which will ignite when it hits the paper. I’m more or less using this http://shardsofthedarkage.blogspot.com/2014/01/venturi-forge-build-part-ii-burners.html as my guide for all this. Let’s hope it works out!

What is cutting?

The line between a “sharp knife” and a “dull knife” is finer than you’d think. When talking about how sharp a knife is or how it all works, you have to delve in almost microscopically to the very edge of the knife. “Cutting” is literally separating a fused substance into two parts.To do this, the very edge of the knife, which you can consider as an edge, is pushed forward into the substance, say a tomato. The edge is pushed against the surface of the tomato, and if you look at it microscopically, the foremost atoms of the knife edge slip in between and push aside the molecules of the tomato, so they are no longer bonded together. To imagine a two-dimensional image of a perfectly sharp knife, edge up, point facing you, would be like a triangle made up of pixels, which are the grains of particles of steel. The edge, at the top of the pyramid, would be the smallest possible size, one particle, or one pixel. This single pixel is stacked and bonded to two more just beneath it, which are bonded to three beneath them, and so on. Imagine a cloud of tomato pixels or particles, descending down onto the point of the triangle. One tomato pixel comes down and touches on top of the topmost steel pixel. The tomato pixel is pushed by more pixels behind and around it, and it cannot be pushed back upwards, so it takes the path of least resistance, to say the right of that steel pixel, breaking the bond with the adjacent tomato pixel, which pushes to the left of the steel pixel. As the cloud of tomato pixels continue to push down, the tomato pixel just above the first, also comes into contact with the topmost steel pixel, and separates to one side. Because the bonds between the steel pixels are stronger than those of the tomato pixels, the very first tomato pixel is pushed to the right of the second steel pixel, rather than left and in between the first and second steel pixels, pushing it further away from the original partner tomato pixel, on the other side of the steel triangle. This continues, pushing the cloud of tomato atoms into two parts, until it has reached the end of the cloud, at which point the cloud of tomato atoms is to completely separate parts. This is an ideal perfectly sharp knife.

Now imagine the same situation, the triangle of steel pixels with the cloud of tomato pixels descending on it once more, but this time with instead of one single pixel at the top of the triangle, there are two (with three below them, four below those, and so on). When the cloud descends down, the nearest tomato pixel pushes against the top two, nestling in the valley between, but not slipping in between them because the steel pixels are too close and will not separate due to extremely strong bonds. The tomato pixels behind and around the first are not separated, rather they just push onto the triangle like a finger against a balloon. Eventually, they only separate from the first tomato pixel because they are stretched so far down the sides of the triangle. However the above situation would be rare, as the chance of that tomato pixel coming down perfectly on top of the two steel pixels is extremely minute. More likely the tomato pixel would separate to one side or the other, especially as tomato particles do not pack as closely together as steel particles. But imagine now if you had five steel pixels as the top layer. In this case they will almost definitely push against the cloud until the tomato bonds break because of stretching. This is an example of a dull knife. Quite often, depending the strength of the material being cut, such as bread, the bread particles will just be pushed upwards, breaking all bonds with the particles to either side. A dull knife cutting is just squishing whatever material is in it’s path, away.

Serrated knives on the other hand, cut by digging away a trench, like a row of shovels. When non-serrated knives are dulled, it is because those few topmost particles on the triangle have been moved to the side, bent out of the way because of tough resistance. Some particles will remain in the original space, while others bend to either side, causing jaggedness, like small serrations. This is why when people accidentally cut themselves with a super sharp knife, they sometimes don’t feel it, or don’t bleed immediately, even though the cut is fairly deep, as opposed to when they cut themselves with a dull knife. The sharp knife has not destroyed tissue, it simply separated the skin into two parts, which touch and are closed again as soon as the knife is removed. A dull knife rips away the tissue in its path, leaving a gaping gash, through which blood will flow freely.

Well, that was longer than I had intended. Hopefully that gives you a detailed knowledge on exactly how a blade cuts, how it dulls, and under what ways it performs and stays performing best.