- Stropping
Stropping consists of running the edge along a piece of leather charged with
some kind of abrasive like stropping paste or green chromium oxide (I had
previously said jeweler's rouge is okay, but have since heard that a more
aggressive cutter is needed). It is done for a short time to finish off the
burr, or for a long time to give the edge a final polish. Stropping is an
easy-to-use finishing step (as opposed to the difficulty in keeping a
consistent angle on a stone).
Before you strop, remember to wash and dry your newly-sharpened knife. If you
don't, you might grind leftover metal particles into the strop itself. If you
need to charge your strop, put a little paste on your fingers and rub it into
the leather.
To strop, you run the edge along the leather with the blade positioned spine
first and the edge trailing (opposite way from sharpening on a stone). With a
thin straight razor, the spine of the razor is always kept on the strop, and
direction is reversed by flipping the razor over along its spine. In my
experience, this isn't necessary with a utility knife. You can strop with the
blade spine raised above the leather (don't lift too high -- if the edge bites
into the leather, that's too high), and change directions by lifting the entire
knife up, turning it over, and placing it back down.
If you've never stropped your knife before, give it a try. It will come out
very sharp, but of course polished and so optimized for push-type shaving cuts.
The strop to some extent can make up for less-than-perfect sharpening technique
-- a sharp knife can be made extra sharp on the easy-to-use strop. However, I
always tell people that they should be able to get their knife scary sharp
without the strop; don't let the strop keep you from recognizing weaknesses and
improving your technique on the hone!
In the absence of a strop (say, out in the field), many people use their jeans
and then their palm as a strop. There's probably no need to point out the
danger in this practice, so don't do it. That said, I must admit to having done
this myself on numerous occasions, and having gotten good results.
A safer and more effective trick is to use cardboard (say, the cardboard back
of a standard notepad). You can optionally charge the cardboard with metal
polish, just rub it in with your fingers. Then strop as above. Even without the
polish, the cardboard will strop acceptably. Stropping with cardboard has
become a de-facto standard last step for sharpening chisel-ground (single-side
ground) knives these days, for burr removal purposes.
- Using a Steel
The sharpening steel should be an important part of your knife maintenance
strategy, and is maybe the most mis-understood part.
When you use a knife for a while, especially a knife with a soft, thin edge
like that found on a kitchen knife, the edge tends to turn a bit and come out
of alignment. Note that the edge is still reasonably sharp, but it won't feel
or act very sharp because the edge may not point straight down anymore! At this
point, many people sharpen their knives, but sharpening is not necessary and of
course decreases the life of the knife as you sharpen the knife away. It's also
akin to putting in a thumbtack with a sledgehammer.
The steel is used to re-align the edge on the knife. Read that last sentence
again. Re-aligning the edge is all the steel needs to do. It does not need to
remove any metal. Since the steel's only function is to re-align, the
sharpening steel can be perfectly smooth and still do its job. You'll see many
bumpy steels on the market, but this is almost certainly because consumers
think that steels must have bumps to work. The bumps can actually mess up the
edge, and make the work of steeling more difficult.
There are two schools of thought on steels. Some people use grooved steels,
which align the edge more aggressively but are harder on the edge. I use a
smooth steel, which is easy on the edge but may align the edge more slowly.
To use the steel, run the knife along the steel on one side using light
pressure -- no more pressure than the actual weight of the knife is required!
Then move to the other side and do it again. Repeat a number of times until
your edge feels sharp and nice again. I hold the steel in my left hand, the blade
in my right, and lightly run the blade along the steel while keeping the steel
stationary, but it's perfectly fine to move both steel and knife past each
other at the same time, or whatever works for you.
Most people run the knife down the steel edge first, the same direction you use
when sharpening. This yields good results. However, theoretically going
edge-first along the steel could bite into the edge while straigtening it, and
so many people like to go spine-first (like when stropping) instead. This
method also works well, and I personally have begun to feel that steeling in
this direction gets my edge the tiniest bit sharper. It is more awkward to go
spine-first, so if you have any trouble with it move to edge-first, and your
edge will end up just fine.
If you steel your knife every time you use it, you will significantly lengthen
the time between sharpenings. I've found steeling to be critical on kitchen
knives, but it's an incredible help even on ultra-hard ATS-34.
Wednesday 30 October 2013
Choosing a stone for your knife
- What Kind of Stone?
Basically, a stone needs to cut metal off the edge. The stones below do this well, and for most of us our time would be better spent actually learning how to sharpen than worrying too much about the minor advantages of one stone vs. another. Get the biggest stones you can afford and have room for. Big stones make the job much much easier.
The time-honored stone is the arkansas stone. Soft arkansas stones provide the coarser grits, with harder stones providing finer grits. Many people use oil on these stones, ostensibly to float the steel particles and keep them from clogging the stone. John Juranitch has popularized the notion that oil should absolutely not be used when sharpening, and indeed results from people using arkansas stones without oil have been very positive. However, if you have ever used oil on your arkansas stone, you need to continue using it, or it will clog. If you never put oil on your arkansas stone, you will never need to.
Synthetic stones are very hard, and won't wear like natural stones (a natural stone may get a valley scooped out of it over time). They clean well with detergent-charged steel wool, I use SOS detergent pads, they clean very very fast and very well. I know you're thinking that cleaning with steel wool will cause the stone to shear off the steel wool and fill up the stone even worse! But I assure you that is not the case, for whatever reason SOS pads clean synthetic stones, they do not make the stones dirtier. Spyderco and Lansky are some manufacturers who sell synthetic stones.
Stones with diamond dust embedded in them cut aggressively. You can remove metal very quickly if you need to, but be careful lest you remove too much too fast! DMT, Eze-Lap, and Lansky are some manufacturers who sell diamond-based hones. Some diamond stones have the problem that the diamond dust wears off quickly, leaving you with a useless stone.
Japanese water stones come in some very high grits -- I've seen all the way up to 8000! These stones are very expensive. The stones sit in a water bath, and a slush forms on top that helps the final polish.
Both Japanese water stones and natural stones will eventually dish out in the center with use. To flatten them back out, put some sandpaper on a flat surface and rub the stone top on it. Wet/dry 400 grit sandpaper mounted on a table top or glass is reputed to work well.
- Water or Oil on My Stone?
Basically, the purpose of the stone is to rub against the blade and remove metal. Slippery liquids, like water and especially oil, make the rubbing slicker, causing less metal to be removed, causing sharpening to take longer. On top of that, as your edge is being sharpened on the stone, the oil-suspended metal particles are washing over the edge and dulling it again.
On an arkansas stone, the oil is supposedly needed to float metal particles away from the stone surface, lest the stone clog and stop cutting. Some people on this group have used their arkansas stones without oil or water, and have reported good results. However, if you've already used oil on your arkansas stone, you'll probably need to keep using oil forever on it, because an already-oiled stone will clog up if not kept oiled. If you have a fresh arkansas stone, go ahead and use it without the oil, and things should be okay.
Japanese water stones are the one type of stone that need water. The stones are designed to work with water, and as you sharpen a small amount of the stone's material breaks off and forms an abrasive slurry along the top.
In any case, the bottom line is: use liquid or don't. Using the liquid will make the sharpening process slower and messier, but if you insist on using liquid and are willing to spend more time, that's up to you.
- How Fine Should My Stone Be? Important notes on grits!
The finer the stone, the more polished your edge will become. The rougher the stone, the more the scratches in the edge function as "micro-serrations" (see also the serrated vs. plain edge ).
Though the actual ontological status of the micro-serrations is debatable (Juranitch says there's no such thing, having looked under a microscope), the serrated effect of the coarser grind is undoubtably there.
The more polished the edge, the better your edge will work for doing push-cut applications like shaving, whittling, peeling an apple, skinning a deer. Also, your cut will be more clean and precise with the polished edge.
A rougher, more micro-serrated edge will work better for slicing-type applications like cutting through coarse rope, wood, etc. The serrations present more edge surface area, and tend to "bite" into the thing being cut.
It is possible to get an edge that will shave hair with a medium (300-400 grit) stone, with practice [I specifically mention stone grits because many manufacturers call the 300-400 grit stones "coarse" rather than "medium"]. The medium stone will have pretty big micro-serrations. In previous version of the FAQ I stated that I find this too rough a finish for my general utility edge. However, I've since found this to be a really nice edge finish for utility work -- it won't shave great, but it does a really nice job on cutting coarse materials.
Anyone should be able to get an edge that shaves hair easily with a fine (600 grit) stone. I find this to be a pretty useful finishing stone, leaving enough micro-serrations for general utility work but still being hair-shaving sharp.
An extra fine stone (1200 grit) should start polishing the edge, and you should end up with a hair-popping sharp edge. This is also a good choice for a general utility finish, especially on a partially-serrated blade, where the serrations can be used when the slightly-polished main part of the blade becomes less effective.
One can buy Japanese water stones with grits up to 8000, which leaves a polished edge that's so sharp, your hairs will jump off your arm when they see the edge coming. I would question this finish on an everyday utility knife which might be called upon to cut through a thick rope or what have you, but it is a finish that works well when a polished edge is called for.
************* IMPORTANT TIP ****************
Many treatises on sharpening tend to focus on getting a polished, razor-like edge. This is partially the fault of the tests we use to see how good our sharpening skills are. Shaving hair off your arm, or cutting a thin slice out of a hanging piece of newpaper, both favor a razor polished edge. An edge ground with a coarser grit won't feel as sharp, but will outperform the razor polished edge on slicing type cuts, sometimes significantly. If most of your work involves slicing cuts (cutting rope, etc.) you should strongly consider backing off to the coarser stones, or even a file. This may be one of the most important decisions you make -- probably more important than finding the perfect sharpening system!
The tests seem to indicate that you should think carefully about your grit strategy. If you know you have one particular usage that you do often, it's worth a few minutes of your time to test out whether or not a dull-feeling 300-grit sharpened knife will outperform your razor-edged 1200-grit sharpened knife. The 300-grit knife may not shave hair well, but if you need it to cut rope, it may be just the ticket!
If you ever hear the suggestion that your knife may be "too sharp", moving to a coarser grit is what is being suggested. A "too sharp" -- or more accurately, "too finely polished" -- edge may shave hair well, but not do your particular job well. Even with a coarse grit, your knife needs to be sharp, in the sense that the edge bevels need to meet consistently.
Basically, a stone needs to cut metal off the edge. The stones below do this well, and for most of us our time would be better spent actually learning how to sharpen than worrying too much about the minor advantages of one stone vs. another. Get the biggest stones you can afford and have room for. Big stones make the job much much easier.
The time-honored stone is the arkansas stone. Soft arkansas stones provide the coarser grits, with harder stones providing finer grits. Many people use oil on these stones, ostensibly to float the steel particles and keep them from clogging the stone. John Juranitch has popularized the notion that oil should absolutely not be used when sharpening, and indeed results from people using arkansas stones without oil have been very positive. However, if you have ever used oil on your arkansas stone, you need to continue using it, or it will clog. If you never put oil on your arkansas stone, you will never need to.
Synthetic stones are very hard, and won't wear like natural stones (a natural stone may get a valley scooped out of it over time). They clean well with detergent-charged steel wool, I use SOS detergent pads, they clean very very fast and very well. I know you're thinking that cleaning with steel wool will cause the stone to shear off the steel wool and fill up the stone even worse! But I assure you that is not the case, for whatever reason SOS pads clean synthetic stones, they do not make the stones dirtier. Spyderco and Lansky are some manufacturers who sell synthetic stones.
Stones with diamond dust embedded in them cut aggressively. You can remove metal very quickly if you need to, but be careful lest you remove too much too fast! DMT, Eze-Lap, and Lansky are some manufacturers who sell diamond-based hones. Some diamond stones have the problem that the diamond dust wears off quickly, leaving you with a useless stone.
Japanese water stones come in some very high grits -- I've seen all the way up to 8000! These stones are very expensive. The stones sit in a water bath, and a slush forms on top that helps the final polish.
Both Japanese water stones and natural stones will eventually dish out in the center with use. To flatten them back out, put some sandpaper on a flat surface and rub the stone top on it. Wet/dry 400 grit sandpaper mounted on a table top or glass is reputed to work well.
- Water or Oil on My Stone?
Basically, the purpose of the stone is to rub against the blade and remove metal. Slippery liquids, like water and especially oil, make the rubbing slicker, causing less metal to be removed, causing sharpening to take longer. On top of that, as your edge is being sharpened on the stone, the oil-suspended metal particles are washing over the edge and dulling it again.
On an arkansas stone, the oil is supposedly needed to float metal particles away from the stone surface, lest the stone clog and stop cutting. Some people on this group have used their arkansas stones without oil or water, and have reported good results. However, if you've already used oil on your arkansas stone, you'll probably need to keep using oil forever on it, because an already-oiled stone will clog up if not kept oiled. If you have a fresh arkansas stone, go ahead and use it without the oil, and things should be okay.
Japanese water stones are the one type of stone that need water. The stones are designed to work with water, and as you sharpen a small amount of the stone's material breaks off and forms an abrasive slurry along the top.
In any case, the bottom line is: use liquid or don't. Using the liquid will make the sharpening process slower and messier, but if you insist on using liquid and are willing to spend more time, that's up to you.
- How Fine Should My Stone Be? Important notes on grits!
The finer the stone, the more polished your edge will become. The rougher the stone, the more the scratches in the edge function as "micro-serrations" (see also the serrated vs. plain edge ).
Though the actual ontological status of the micro-serrations is debatable (Juranitch says there's no such thing, having looked under a microscope), the serrated effect of the coarser grind is undoubtably there.
The more polished the edge, the better your edge will work for doing push-cut applications like shaving, whittling, peeling an apple, skinning a deer. Also, your cut will be more clean and precise with the polished edge.
A rougher, more micro-serrated edge will work better for slicing-type applications like cutting through coarse rope, wood, etc. The serrations present more edge surface area, and tend to "bite" into the thing being cut.
It is possible to get an edge that will shave hair with a medium (300-400 grit) stone, with practice [I specifically mention stone grits because many manufacturers call the 300-400 grit stones "coarse" rather than "medium"]. The medium stone will have pretty big micro-serrations. In previous version of the FAQ I stated that I find this too rough a finish for my general utility edge. However, I've since found this to be a really nice edge finish for utility work -- it won't shave great, but it does a really nice job on cutting coarse materials.
Anyone should be able to get an edge that shaves hair easily with a fine (600 grit) stone. I find this to be a pretty useful finishing stone, leaving enough micro-serrations for general utility work but still being hair-shaving sharp.
An extra fine stone (1200 grit) should start polishing the edge, and you should end up with a hair-popping sharp edge. This is also a good choice for a general utility finish, especially on a partially-serrated blade, where the serrations can be used when the slightly-polished main part of the blade becomes less effective.
One can buy Japanese water stones with grits up to 8000, which leaves a polished edge that's so sharp, your hairs will jump off your arm when they see the edge coming. I would question this finish on an everyday utility knife which might be called upon to cut through a thick rope or what have you, but it is a finish that works well when a polished edge is called for.
************* IMPORTANT TIP ****************
Many treatises on sharpening tend to focus on getting a polished, razor-like edge. This is partially the fault of the tests we use to see how good our sharpening skills are. Shaving hair off your arm, or cutting a thin slice out of a hanging piece of newpaper, both favor a razor polished edge. An edge ground with a coarser grit won't feel as sharp, but will outperform the razor polished edge on slicing type cuts, sometimes significantly. If most of your work involves slicing cuts (cutting rope, etc.) you should strongly consider backing off to the coarser stones, or even a file. This may be one of the most important decisions you make -- probably more important than finding the perfect sharpening system!
The tests seem to indicate that you should think carefully about your grit strategy. If you know you have one particular usage that you do often, it's worth a few minutes of your time to test out whether or not a dull-feeling 300-grit sharpened knife will outperform your razor-edged 1200-grit sharpened knife. The 300-grit knife may not shave hair well, but if you need it to cut rope, it may be just the ticket!
If you ever hear the suggestion that your knife may be "too sharp", moving to a coarser grit is what is being suggested. A "too sharp" -- or more accurately, "too finely polished" -- edge may shave hair well, but not do your particular job well. Even with a coarse grit, your knife needs to be sharp, in the sense that the edge bevels need to meet consistently.
Tuesday 29 October 2013
The how to knife sharping guide
Ok over the next 3 weeks i will be writing on my own knowledge of knife sharping and i will be chatting to some experts to get their opinion. I for years could put a sweet edge on a knife with a stone but could never use a steel. Why? because i never knew steels don't sharpen knives! they clean up and straighten the edge. the end result is a knife that cuts well again, but the difference of sharpening and straightening and edge is important. I had always tried to sharpen my knives with a steel and got poor results. More on this later.
So this will discuss the central elements of sharpening, and then go on to sharpening angles, hones, sharpening systems, the latest fads in edges (e.g., chisel grinds). This will show you how to get a burr and grind it off to end up with a sharp knife.
When many hunters try
to sharpen a knife, the knife actually gets duller! If it's any consolation, I have
been there too and steals where a headache for me for years. The best way is to
study sharpening fundamentals, and then use some kind of sharpening system that
pre-sets the angles. That way, you can begin by learning how to raise a burr,
feel for the burr, and then grind it away, without having to worry about
keeping the angle consistent as well. When you understand how to sharpen, then
you can get rid of the rig, buy some flat hones, and learn how to sharpen
freehand.
so i will be covering these areas.
The Fundamentals of Sharpening
- Getting a Sharp Edge
Here's a short review of the sharpening process. If this section is confusing . Many of the subjects in this section (e.g., stone grits) are explained later
You grind one edge along the stone edge-first until a burr (aka "wire") is formed on the other side of the edge. You can feel the burr with your thumb, on the side of the edge opposite the stone. The presence of the burr means that the steel is thin enough at the top that it is folding over slightly, because the bevel you've just ground has reached the edge tip.
If you stop before the burr is formed, then you have not ground all the way to the edge tip, and your knife will not be as sharp as it should be. The forming of the burr is critically important -- it is the only way to know for sure that you have sharpened far enough on that side. Once the burr is formed on one side, turn the knife over and repeat the process.
So, you've sharpened one side only until you felt a burr along the entire length of the opposite side, then you move sides and repeat the process.
Do not follow the directions that come with many sharpeners, of the form "Do 20 strokes on one side, then 20 strokes on the other". You go one side only until the burr is formed; if that takes 10 strokes or 50 strokes, you keep going until you get a burr, this is an art and all steel and stone are different. Only then do you flip the knife over and do the other side.
Having raised a burr, our job now is to progress to finer stones, in order to make the edge smoother and remove the burr. So now we run the blade along the stone from end to tip, this time alternating sides with each stroke. Move to a finer stone, and then do it again.
Sometimes, the burr is turned directly downwards during sharpening, and since it is very thin and razor sharp, it seems like an incredible edge. This is called a "wire edge". But being fragile, it will break off the very first time you use the knife, leaving you with an extremely dull knife. If you seem to be getting good sharpening results on your knives, but they are getting dull very quickly with little use, you may be ending up with a wire edge. If that's the case, you'll need to be careful and watch out specifically for a wire edge; you should try progressing down to finer stones, try double-grinding the edge, and give the knife a quick stropping once you're finished (all these terms are explained below). If your knife is fading fast as you're sure it's not because you left a wire edge, steeling between uses may be what you need. My last few strokes on the stone become progressively lighter, to avoid collapsing the edge and raising another burr.
On a badly-worn or damaged edge,start with a medium (300-400 grit) stone, then move to a fine (600 grit) stone, and then sometimes finish on an extra-fine (1200 grit) stone for more polished edge. However, once the knife is sharp try tore-sharpen before it gets too worn down. In that case, start on the fine stone. But be sure to read the important notes on grits later
Lastly, you may use a leather strop on the knife.
On other sharpening systems, the same fundamentals as laid out above still apply. For example, on a V-type sharpener, I'll start by sharpening one side only against the right-hand stick until a burr forms. Then I move to the other stick until a burr forms. Only after I've raised a burr from both sides will I follow the manufacturer's directions and alternate from one stick to the other between strokes.
- What Angle?
The smaller the angle, the sharper your knife will feel. But the smaller the angle, the less metal that's behind the edge, and thus the weaker the edge. So your sharpening angle will depend on your usage. A surgeon's blade will have a very thin, very low-angle edge. Your axe will have a strong, thick, high-angle edge.
Something like a razor blade will having an angle of around 12- degrees, and it's chisel-ground so that's 12-degrees total. Utility knives will have angles anywhere between 15- and 24- degrees (30-48 degrees total). An axe will have something around a 30-degree angle.
For double-ground utility knives, a primary edge of 15-18-degrees, followed by a secondary grind of 21ish-degrees, works well. Don't be obsessed with getting the exact right angle; rather, make sure that at whatever angle you've chosen, concentrate on holding it precisely.
See also the sections on convex edges and chisel-ground edges.
So this will discuss the central elements of sharpening, and then go on to sharpening angles, hones, sharpening systems, the latest fads in edges (e.g., chisel grinds). This will show you how to get a burr and grind it off to end up with a sharp knife.
so i will be covering these areas.
1. Sharping
Fundamentals -
a.
Get
a sharp edge
b.
Angle?
c.
What
stone?
d.
Oil
or water stone?
e.
How
fine should the stone be?
f.
Important
notes on grits!
g.
Stropping
h.
Using
a steel
2. Freehand
tips and tricks –
a.
Why
does my knife go dull so fast?
3. Sharpening
Differently Ground Blades –
a.
serrated
blades
b.
The
Moran (Convex) edge
c.
The
chisel-ground edge
4. Overview
of various sharpening systems –
a.
Clamp-on
sharpening guides (Razor Edge, Buck, etc.) –
b.
Clamp-and-Rod
rigs (Lansky, Frost, etc.)
c.
V-type
sharpeners (Spyderco Triangle, etc.) –
d.
Other
miscellaneous
Freehand sharpening,
and its wondrous advantages!The Fundamentals of Sharpening
- Getting a Sharp Edge
Here's a short review of the sharpening process. If this section is confusing . Many of the subjects in this section (e.g., stone grits) are explained later
You grind one edge along the stone edge-first until a burr (aka "wire") is formed on the other side of the edge. You can feel the burr with your thumb, on the side of the edge opposite the stone. The presence of the burr means that the steel is thin enough at the top that it is folding over slightly, because the bevel you've just ground has reached the edge tip.
If you stop before the burr is formed, then you have not ground all the way to the edge tip, and your knife will not be as sharp as it should be. The forming of the burr is critically important -- it is the only way to know for sure that you have sharpened far enough on that side. Once the burr is formed on one side, turn the knife over and repeat the process.
So, you've sharpened one side only until you felt a burr along the entire length of the opposite side, then you move sides and repeat the process.
Do not follow the directions that come with many sharpeners, of the form "Do 20 strokes on one side, then 20 strokes on the other". You go one side only until the burr is formed; if that takes 10 strokes or 50 strokes, you keep going until you get a burr, this is an art and all steel and stone are different. Only then do you flip the knife over and do the other side.
Having raised a burr, our job now is to progress to finer stones, in order to make the edge smoother and remove the burr. So now we run the blade along the stone from end to tip, this time alternating sides with each stroke. Move to a finer stone, and then do it again.
Sometimes, the burr is turned directly downwards during sharpening, and since it is very thin and razor sharp, it seems like an incredible edge. This is called a "wire edge". But being fragile, it will break off the very first time you use the knife, leaving you with an extremely dull knife. If you seem to be getting good sharpening results on your knives, but they are getting dull very quickly with little use, you may be ending up with a wire edge. If that's the case, you'll need to be careful and watch out specifically for a wire edge; you should try progressing down to finer stones, try double-grinding the edge, and give the knife a quick stropping once you're finished (all these terms are explained below). If your knife is fading fast as you're sure it's not because you left a wire edge, steeling between uses may be what you need. My last few strokes on the stone become progressively lighter, to avoid collapsing the edge and raising another burr.
On a badly-worn or damaged edge,start with a medium (300-400 grit) stone, then move to a fine (600 grit) stone, and then sometimes finish on an extra-fine (1200 grit) stone for more polished edge. However, once the knife is sharp try tore-sharpen before it gets too worn down. In that case, start on the fine stone. But be sure to read the important notes on grits later
Lastly, you may use a leather strop on the knife.
On other sharpening systems, the same fundamentals as laid out above still apply. For example, on a V-type sharpener, I'll start by sharpening one side only against the right-hand stick until a burr forms. Then I move to the other stick until a burr forms. Only after I've raised a burr from both sides will I follow the manufacturer's directions and alternate from one stick to the other between strokes.
- What Angle?
The smaller the angle, the sharper your knife will feel. But the smaller the angle, the less metal that's behind the edge, and thus the weaker the edge. So your sharpening angle will depend on your usage. A surgeon's blade will have a very thin, very low-angle edge. Your axe will have a strong, thick, high-angle edge.
Something like a razor blade will having an angle of around 12- degrees, and it's chisel-ground so that's 12-degrees total. Utility knives will have angles anywhere between 15- and 24- degrees (30-48 degrees total). An axe will have something around a 30-degree angle.
For double-ground utility knives, a primary edge of 15-18-degrees, followed by a secondary grind of 21ish-degrees, works well. Don't be obsessed with getting the exact right angle; rather, make sure that at whatever angle you've chosen, concentrate on holding it precisely.
See also the sections on convex edges and chisel-ground edges.
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