20 November 2014

Knives: Cuts and sharpness

Some time ago I got interested in improving my kitchen cutting technique,  mainly cutting-board cutting.  So I looked what youtube had to offer.  Cutting an onion on youtube is nearly a standard but there is not much variation on it. Or rather any demonstration not perfectly meeting the standard will massively be downvoted by professionals and youtube specialists alike unless it concerns a Japanese suchi champion.

The cuts.  Knife cuts get really interesting when spooncarving and such high risk activities with its numerous variations.  When cutting to the board I see three main movements:  1. The push-cut straight down to the board, that's also chopping.  2.  Slicing,  moving the knife moves mainly forward from tip to heel or vice-versa. There is also repetitive-slicing (sawing) as a variation on slicing, I use it when cutting large peaces of meat or bread or with a blunt knife. 3. The skewed cut,  when the tip rests on the board and the knife is pulled backward.
Important is that a knife may be too blunt for a push cut and be perfectly fine with slicing and skewed cuts.

Cutting and sharpness.  A sharp knife is a safe knife and all that.  But things are not that simple.  This picture from a video by Virtuovice shows a razor sharp knife doing a push-cut through an apple.  I don't think the sharpness of the blade is of any help, a completely blunt but narrow knife would cut better and straighter. For Virtuovice it's probably not a problem as he uses his knives to cut meat.  When peeling the apple,  still a push-cut, the sharp edge can be used as the thin peel can be pushed away. But here again a thin, narrow bladed parring knife will be in line with the cut and need less effort.
When parring I look for a balance in sharpness.  If the blade is too sharp I will cut my fingers who are holding the apple,  too blunt and I will need to saw cut to peel.  So I need a Goldilocks blade able to push cut the apple,  but not my fingers.  When cutting to the board,  my fingers are less at risk. I then can go for a sharper blade or I can use the more effective slicing and skewed cuts.

Cutting an onion  After trying out the big (chef's) knife approach,  I came back to using a paring knife to cut vegetables on the cutting board. And that's what most people I know do.  I go for a medium sharpness,  sharper than many households here but less than many professionals and certainly less than some sushi knives.

A sharpish thin bladed parring knife can cut onions like butter and gives a good result,  a chef's knife is not  necessarily better or easier. The cut used is a folded cut: from the tip slicing until nearly touching the board coming back with a skewed cut. And maybe there are less tears when the open onion surface is minimal.

As a matter of fact the same cutting technique with a ten year old factory edge (that's blunt) table knife is no fun,  but still offers acceptable results.
An ever harp knife
I sometimes hear people claim to never sharpen their parring knife.  Mostly it concerns the (razor) thin carbon version of the parring knife I use with an edge of maybe 5 degrees per side.
Looking at Cliff Stamp post about edge retention at lower angles, one can see a confirmation of that as their is a clear distinction between 25 dps and 13 dps.  13 dps cuts on and on,  only slowly achieving a too blunt state, where the edge of 25 dps dissapears fast to an unusable state
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17 October 2014

Knives: Sharpening angles

Personally I am an angle extremist as my main (vegetable) kitchen knife has a micro bevel of 14° (or 7 degrees per side).  Great but this time I wanted to sharpen a camping knife,  so which angle to choose?

Googling for data I get the following.  Looks good  ...  although 35° that's not much for a cleaver ... are machete in the same category as cleavers ... then I got it, these are sharpening angles, so the edges start at 24° to go up to 70° ...??? ... Welcome to the 21st century!

Second attempt and back to last century,  I took The complete guide to sharpening by Leonard Lee (1995).  I found a rather pragmatic approach:  for kitchen knives anything between 10° (5 dps) to 35° where the major aspect is finding an angle that is easy to reproduce when sharpening.
For camping knives he proposes 30° when whittling and 15° when mainly handling meat. I am not sure I agree there as I expect that when cutting meat from bones there is more strain on the edge. And a blade that doesn't 'bite' the bone too easily is more comfortable.

Looking at factory angles
Morakniv  knives do talk about angles, they are not in microbevels and propose 23° (12 dps) and 27° (14 dps) for their heavier 3.2mm (1/8") thick bushcraft knives that need to withstand batoning.  It is surprising they go to the American bushcraft market with anything thinner than 1/4". They are probably more hard headed traditionalists than marketeers.
Opinel knives, I couldn't find anything on their site.  Someone talked about 25° as recommended by them,  a sharpening angle so that's 25 dps.  It sounded so ... 21st century that I checked.  It's true, the picture shows the main reflection from the convex blade, but at 25° there is the reflection of the micro bevel.
For the old Opinel blades I can't see the factory edge anymore, but remembering the ease at wich they dented I guess 10° (5dps),  the blades were not yet convex then.

Now why do I think 50° (25 dps) is excessive.  When looking at plane blades I see angles of  25-35° used with the blade off center, that is not in cut but rather a scraping movement and regularly slammed with great force (6# of plane and the guy behind pushing with his two hands) against knots that represent a localized high resistance point. Apart from chopping bones there are few situations worse than that.

On youtube I found Canadian Cliff Stamp talking about Edge retention as a function of micro-bevel angle
and offering new perspectives on optimal angles.  He's someone who seem to spend his free time sharpening and cutting truckloads of wood, cardboard, rope and old carpets to assess his sharpening. This delivers interesting work and results.
What he says is that edge retention increases with smaller angles up to some usage-user dependent tipping point. On the graphic 13 dps does 4 times better than 25 dps.  I guess that the graphic stops at 13 dps because he uses a Wicked Edge sharpening gig to set precise angles. Thus losing the ability to go for low angles, the jig being a 21st century product and all that. The Wicked Edge minimum of 13 dps is a lot more than the Leonard Lee lower limit of 5 dps.
The reason behind the improvement are twofold:  low angles cut with less strain so less wear and they offer more 'meat' before the edge becomes too blunt.

So the micro bevel for the camping knife? Whatever I want,  maybe 30° (15 dps) to follow Leonard Lee, probably less.


30 September 2014

Fast holdfast

I got hold of a French holdfast with cam lever.  Having already mentioned them in a previous post,  I found one on a French second hand list and got acceptable shipping costs.  I imagine it as an early seventies model.
It weights 2,5kg (5#).  So it's maybe heavy enough to be set without hammer,  but in practice there is too much play in the hinges to throw it in place.

Not that setting is a problem,  the promise of a one handed operation is fulfilled. And there is plenty plenty of room for even more pressure.  The only problem is maybe the weight, disengaging 2,5kg out of a narrow hole is nothing light.  I glued a thin strip of soft wood (populus nigra) under the pressure point, to give the holdfast a softer touch.  An iron fist on a poplar shoe.


The model is still sold under a more modern form ... that's more the eighties (?) as design.

It looks as if they use a thread,  so it's already close to the 'English' model from Axminster but with the handle in between and not on top. And Veritas too does something similar.

And now that we are at it Sjöbergs has a different approach for something similar,  but it works nevertheless




08 July 2014

Knives: EDC knife usage

After presenting his everyday cary (EDC) Adam Savage worked at a holder for his Leatherman on youtube. So yes those shiny pocketable knives and multitools,  I think I need them,  but what for?

Every day use like opening packages and letters,  cutting fruit, ... and many other things, I hear. So I went for youtube in search of the 'many other things' as  there are many EDC knife demonstrators there, daily carrying up to five blades.  Listing what I heard the main usages for a knife are: showing one more knife, repetitive fast one handed opening, tactical use, cutting paper and battoning. Yes, and on youtube the main usages of a plane are making thin shavings from a perfectly flat scrap of fine wood and setting them on display shelves.  So the knife usages:

Showing one more knife
To do that I ransacked my storage and came up with some, and for good measure bought two extra online.
From the seventies, my camping knives: A non locking folding knife (a nameless maniaghese-hippekniep),  his Opinel n° 8 replacement, a second thoughts Opinel n° 10 (4" blade),  just to be able to cut bread decently. I added now a new shiny stainless Opinel.
A pocketable-keychain leatherman, pink for a good price, but then I have to find a use for pliers.  Maybe it's more something for fishing.
Two pocketable Victorinox.

Fast one handed opening
I can one hand open my Opinel in maybe 4 seconds (with and without usage of the Opinel knock),  but that's way slower than American knife slingers and the closeness of my thumb to the edge would get too much attention of the youtube safety brigades.  Although ... there is no such thing or rather I am part of that posse, having seen so many people slide their fingers over blade edges. It's sharp or it isn't, there is no try. I found sharp with my first, factory sharp, Opinel, using just the weight of the blade (0.5 oz).  Sharp is safe, they say, whatever safe is.

Tactical use
The stab and slash jobs. Many American knives have a tactical look and are categorized as such,  but apart from that I do not hear much self incriminating talk or demonstrative tactical usage on EDC youtubes.   Personally I had some formal knife fighting training,  but in practice I am even too slow to run away. Anyway what I can legally carry here are knives as a tool not as a weapon.

Cutting paper
I am not so good at sharpening but yes it's not a problem if the test is on thick enough paper.  Shaving is another story, although I like to quote the following "I have found the diameter of human hair to range from 17 to 181 µm" to explain part of my problem. I expect the thickest hair to be 1000 times stiffer and way easier to cut than a thin hair.

Battoning
I made many campfires without any knowledge of battoning (that's using a knife as a froe but without any leverage) even if I have to believe youtube, it is the main bushcraft® knife skill together with the use of ferro rods on the back of the knife. On the other hand splitting wood to make a Swedish torch seems a good way to make a smokeless, low maintenance fire. [edit]Seeing later on a Mors Kochanski presentation I was pleasantly surprised to see more than the usual bare bushcraft® basics.

Eating fruit
Rather not.  I can of course, and for example an Opinel does a decent job.  But I usually cut fruit and vegetables with a low angle blade (7+7=14° micro bevel), so a more standard edge (up to 20°+20° and more), even razor sharp, doesn't cut it, it just splits.  The added problem is the need to clean the blade before closing the knife.
A Japanese knife person, Virtuovice made an illustrative video of the apple problem on youtube with one of his hunting knives.

Opening packages
I receive my packages on a predictable place and that's close to my kitchen parring knives. The only way for a pocket knife to enter the competition is a fast one handed draw.  Speed is what Adam Savage was going for, with his multitool belt holder.

Cutting ropes
As a boy scout we did extensive amounts of rope joinery.  The only tool needed is a saw and a knife (or scissors) to cut rope.  Cutting rope with an axe was the alternative,  but things can and will go wrong with an axe and then the whole joint needs to be redone.

Hunting
A good use of a knife,  I think that cutting meat is one of the main traditional reasons to carry a knife, but it is not my problem.  Surprisingly some hunters say to have worked with mid sized, and even out of necessity with the smallest Victorinox knives.

Whitling
Is seldom mentioned as an EDC knife usage, but it's a good reason to carry a knife.

Pen knife
When I asked my father he said that he carried one in the thirties, he used it as a pencil knife as sharpeners where not common then.  Pens where already in metal so no real pen-knife-manship.  The other reason given was tradition, as a part of 'formal' wear.

Maintenance
Sharpening and such, the Lincoln way (If I had eight hours to chop down a tree, I’d spend six sharpening my axe):  The art of knife maintenance.   There is for example a Japanese who thinks that all Opinels even the old ones are shiny, he calls it To assembly from degradation of OPINEL it's not only poetic but also very thorough. Me it's all about nicks (I call them serrations) and stained steel. And seeing the stamps and the wood choice, mine are maybe a decenium older.

So?
I decided to try it out by adding to my EDC a smallish Victorinox (with pen) in my pocket, I think the flat screw driver used for prying is more useful than the knife.  Technically: it's the Signature Lite,  where I had the tinner Signature (without light) in mind. I already used each of the five utensils once.  Yeah! ... but mostly at home

On my desk I already had, not a multitool but, multiple tools like screwdrivers and scissors,  I added a shiny Opinel blade to see if it can be useful.