Sharpenatrix upgrade

My Sharpenatrix was working well enough but having to tighten the screws holding the blade each time was a bit annoying. So I bought some stainless-steel non-magnetic screws and a bunch of neodymium magnets to play with. And some of those magnets were small cylindrical magnets with a screw, and those were ideal for a quick upgrade of the Sharpenatrix.

Here is a composite picture of the upgraded thingy.

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I screwed three magnets into the end of a 5 mm strip of aluminum, glued on it another strip to make a continuous plane with the magnetic side of the magnets and I used the non-magnetic screw to make an end-stop to lean the back of the blade against. Spanning the blade is now a matter of seconds and whilst the magnets do not hold it extremely strongly, they do hold it strong enough to keep the constant angle during sharpening. And they allow me to adjust the blade position slightly and quickly, giving me greater versatility.

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The screw can be adjusted to the thickness of the blade but its purpose is not to hold the blade firmly – that is done solely by the magnets – but to avoid levering/twisting the blade off the magnets when I lean it against the belt. The side with the screw is now significantly thinner than the side with the magnets, which allows me to sharpen at a constant angle blades that were too narrow for the previous version.

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I have not actually tested it yet, I do not have any knives that need sharpening right now but I see no reason why it should not work.

I have also bought 500 5x5x5 neodymium magnets for making more sophistimacated magnetic chucks in due course.

Some Knives Again – Part 3

This is the second three-piece set from the second overabladeance that I have finished. It is what you might call “vegan” set, because there are no animal parts involved in this one, it is made purely from plant material – black locust and coconut shell.

© Charly, all rights reserved. Click for full size.

© Charly, all rights reserved. Click for full size.

© Charly, all rights reserved. Click for full size.

It is more or less a direct, slightly simplified, follow-up of the experimental knife set. This time the surfaces are not oiled but sealed with epoxy and buffed, just like with the jatoba&bone set from yesterday.

I hope to be able to put all three sets on the shoppe tomorrow. More pictures are, again, on Instagram.

Some Knives Again – Part 2

In the second overabladeance were three tree-knives sets, two of which are finished now.

The first one is from jatoba and cow bone.

© Charly, all rights reserved. Click for full size.

© Charly, all rights reserved. Click for full size.

As is usual, the cow bone has had some pores that accrued the reddish dust from the jatoba during work despite my best efforts to seal the surface of the bone with epoxy before sanding and polishing the handles. At least that way it is clear that it is a real bone and not some synthetic substitute, I guess? The number etching on the chef knife is a bit smudged. I still do not know why it behaves wonky from time to time – on one and the same piece of steel it can happen that I etch one part crisply without problems and a few cm besides that it suddenly does not work properly.

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Fitting the rounded bone pieces to the extremely hard jatoba wood was not exactly easy but I managed a reasonably good fit in all nine instances. On this set, I have infused the surfaces with resin, smoothed them with 600-grit paper, and then coated them with resin again. Only after that did I buff it. Thus the whole set has extremely hard surfaces and it is a bit shiny.

I do know that this whole set is suitable for like 99% of all imaginable kitchen works because it is based on an experimental knife set I wrote about previously which has been very thoroughly tested by now. I have used it to cut both veggies and meat, gut fish, and de-bone chicken and there was a knife in this set for all the tasks that I could think of. This set is slightly modified – the blades are pointer and they do not have round-heeled ricasso. I like rounded tips and round-heeled ricasso but I did not convince many people about the advantages of round tips on knives and blades without ricasso are easier to make.

Again, the set will be for sale in the shoppe sometime towards the end of the week and there are more pictures on Instagram.

Some Knives Again – Part 1

I finally got time to work on knives again and finished some of the second overabladeance blades and two of the first one.

First a set made from an apple branch fork. I have left some of the woodborer’s lacework visible, most of which was just below the bark. Deeper holes and cracks were filled with brown-dyed epoxy.

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The stand and the handles are made from one piece of wood and the grain on the handles is a continuation (plus-minus a few mm) of the grain in the bloc. I added some solder weight to the bottom of the bloc so it is heavier and more stable because I did not want o disturb the shape by adding legs. I aimed for a more flowing and organic look and two straight metal legs would distract from that. I also have tacked on a few anti-friction pads.

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It was not easy to make the slits for the blades so they are a bit rough around the edges but that is OK and in line with the design. When I was deciding how to close the back of the slits, the nearly invisible seamless gluing of flat boards that I do for straight bloc designs was not an option so instead of trying to hide it, I opted for a bold contrast. I glued in a black-locust strip and I have left enough space for a dark-brown epoxy strip around the edges too.

© Charly, all rights reserved. Click for full size.

The bigger knife has some chatoyancy in the handle, something that I did not expect. But I did not make the wood too shiny – I only sealed it with one epoxy dip and I did not seal it for a second time like I do for shinier surfaces – I have just buffed and waxed the set. Thus all the wood has a somewhat satin look to it and the handles are nicely grippy.

© Charly, all rights reserved. Click for full size.

The bigger blade has a minor etching defect near the handle that I thought would be hidden under the scale but It is not, unfortunately, because I made a slight mistake in the glue-up. Also, the blade is slightly thicker and heavier than is typical for this type of my knives, it has a somewhat “choppy” feel to it. All in all, it is a mixed bag as usual, I am not proud of the work I did, but I do not hate it either.

Sometime during this week, the set will be available in the shoppe. There also are slightly more pictures on Instagram.

Plush of the Month: Meet Ferdinand and Sweetie

We haven’t had a plush in a while now, for a couple of reasons. For one, the patraeon patterns I was getting were either not quite my style, or so elaborate that I wasn’t feeling up to them. Not for lack of skill, but for lack of patience and time. I need a bit of instant gratification from my hobbies, so spending weeks on a project didn’t appeal to me. Also, with my back fucking up, sitting was painful and I needed to conserve my sitting down time. But my back got better (damn, you , exercise) and the little one came to me with a project. She’s in the school cheerleading team. Now I must clarify for my American readers: we do not have a school football team. While there are American Football clubs here and they do have cheerleading teams, it’s also purely done as the amazing sport that it is (and deserves recognition), so one of the teachers who loves cheerleading and is involved with a sports club cheerleading team is also training the school team. Their school team is the Flying Bulls (because the teacher’s team has a similar name) and she wanted to make a mascot. We went pattern shopping and soon created Ferdinand (named after this good fellow). Of course the wings were not included, so I had to make up my own pattern for them, but he turned out really cute:

Black plush bull with white and green wings sitting on a table

©Giliell, all rights reserved

Black plush bull with white and green wings full frontal view

©Giliell, all rights reserved

Black plush bull, face close up

©Giliell, all rights reserved

Isn’t he handsome? The eyes are made from epoxy and UV resin and secured with screws. The wings get their stability from pipe cleaners. While Ferdinand was a big hit with the cheerleading team, saying goodbye was hard and I needed something to comfort me. Well, why not make another plush? I have to say that Ferdinand is a completely different style from the last plushies I made and I quite liked it. Instead of the machine embroidery, these designs live from old fashioned eyes and designs. The creator has a couple of plushes in that style and one of them is my favourite animal, a hippo, so I had to go for it. Please meet Sweetie:

Grey hippo plush sitting on a couch, full vieew

©Giliell, all rights reserved 

Grey hippo, torso and arms

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Grey hippo, view from above

©Giliell, all rights reserved

Yes, she’s incredibly adorable. It’s amazing how much of that look comes from adding the eyelids. Depending on how you place them, you get dreamy, sad or angry. She’s moved in with us and has become a full member of the hippo crew. I hope she can brighten your day a little as well.

Sciencing Sharpness – Part 5 – My Sharpening Kit

I have found a blunt-ish knife, one that I use in the cellar to open wooden briquette packages. It was not exactly blunt but it was slightly blunt and I have run it over a quartz stone to make it blunt. It is a knife from high-quality stainless steel but it has been sharpened so much that it has lost about 30% of its width. I have tested with it my traveling sharpening kit. I have done completely freehand sharpening, holding the stone in my left hand and knife in the right hand, no angle measuring, not even angle estimating, just putting the blade to the stone in a way that “feels right” and going on from there like I used to before I got the machinery to be precise. I tried to look up on the internet the grits of the stones that I use but it ain’t easy because one of them is a no-name generic grey carborundum whetstone and as you will see, it does not appear like I found the right ones. I have also used all of the orange thread that I have reinforced with PVA glue and from now on I will use the nylon thread since I have already bought it.

Here is the picture that’s worth a thousand words:

© Charly, all rights reserved. Click for full size

And here are less than a thousand words explaining what’s in the picture:

It is a bit strange that the fine grey layer of the cheap whetstone does not perform much better than the coarse layer and even performs worse than the beige layer on the colored stone which should have slightly coarser grit. There are several possible explanations or a combination thereof – I got the grey stone grits wrong, I done did do a bad job with this layer, or the fact that this stone uses a weak binder and sheds grains very easily plays a role, or I messed up the measurements. Nevertheless, the knife was capable of cutting freely hanging printing paper at this point, although not very easily, and it did bite into a fingernail.

Anyhoo, the second stone is much harder and I actually know the exact grits from the manufacturer. And once I got to the red layer with “just” 500 grit, the knife was shaving-sharp. The leather strops might have burnished the edge a bit but there is no statistically significant difference anymore from the 500 grit stone. It looks like there might be one, a very minor one if I had performed more measurements or had a more precise method.

I would say that it is pretty convincing for my argument that a two-layer whetstone and a strop are all that is needed to get and keep knives sharp.

It also appears like 500 grit stone is sufficient to maintain a knife edge shaving sharp without any further ado. But I would say that shaving hair with the stropped knife feels slightly “smoother” on the arm than with one that went just over the stone and I feel inclined to trust my skin sensors (they are much more sensitive than the kitchen scale after all) on this issue so I’m not convinced that the strop is completely useless. Measuring as fine differences as these might be is not a task that can be done with a rigged-up kitchen scale.

Sciencing Sharpness – Part 4 – Failing to Improve the Measurements

My mother was ordering some things from an online drugstore and I jokingly said if she could order me a nylon thread too. And surprisingly, the shop did carry a 0.25 mm nylon thread. It arrived today. I have immediately run an experiment to evaluate if it delivers better results than my old, PVA glue-impregnated thread. And sadly, it does not.

I made 25 measurements with both threads with a razor and then with the testing knife sharpened at 10°. And the results are interesting, but not good.

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The nylon thread performed statistically significantly better for the razor – the values were less spread out. But when it came to the knife they were both about the same, with no statistical significance whatsoever. And there were outliers in both sets. A disappointment, really. A lower spread would allow me in the future to get useful results with fewer measurements per each test, this way I am somewhat stuck with making at least ten measurements.

At least all four sets had normal distribution which means that averaging multiple measurements should give precise-ish results.

I think that the biggest problem is the scale’s lack of a Hold function and the frequency at which it renews the display. Well, it is still useful and the thread did not cost too much. And it is easier to span.

Sciencing Sharpness – Part 3 – Angle vs. Sharpness

It is not good for my ego to have the predictions mostly correct again, but this time there were things that surprised me a bit.

I have included a sharpening angle of 10° which I never use in praxis because it is not recommended for the N690 steel due to reduced edge retention at that angle (tendency to chipping), but that would not be a problem in this test and it is a data point of knowledge in case I make some carbon-steel sushi knives or razors in the future.

Now the boxplot:

© Charly, all rights reserved. Click for full size

So I got the prediction about how the cutting force will rise mostly correct. Mostly, not completely.

ANOVA test has found no significant difference between the first four angles but I am sure there would be one if I had performed more measurements and/or refined the testing method. The Lookandsee test does indicate a slow rise in cutting force from around 25 gf to around 50 gf.

The jump at 30° is a bit more sudden than I expected. I suspect that it is a fluke. And then the rise at 40-45° was a lot less than I expected.  It seems that the 90° cutting edge is still significantly better than no cutting edge, which would be somewhere around 3-4 times worse with a cutting force of around 1000 gf. I did not expect that. The best-fit function is quadratic. This is less drastic than the predicted exponential growth, although still significantly faster than simple linear growth.

So in conclusion, it does appear that my opinion that whilst there is a difference at angles 10-25°, it is not big enough to matter for casual knife users is substantiated. The angle 30° performed slightly worse than I expected, and the angle 45° performed significantly better than I expected.

I am going to think about all this some more and then I decide how to proceed from now on.

Sciencing Sharpness – Part 2 – Grit vs Sharpness

Notwithstanding dangerousbeans’s comment at the last article, I did find in my steel offcuts pile a blade that broke after it was nearly completely finished, with etched logo and all. That means learning about the sharpening properties of exactly the steel that I use in exactly the state it is in a finished product. In different steel, the results might come out a bit differently, which means I am mightily glad that I could do my tests on this – an absolutely ideal testing specimen.

© Charly, all rights reserved. Click for full size

I have sharpened the blade stub at a 15° angle which is the angle at which I usually sharpen kitchen knives, and always those that I make from N690 steel. (When tasked with sharpening store-bought knives from unknown steel I occasionally sharpen them at 20°, especially if it is clear from the state of the knives that the customer is not particularly careful about their use.)

I established the bevel with 120 grit and then I progressed from 180 and 240 grit Zirkorund and then Trizact belts (in the evaluation translated into grit equivalents) from A 65 all the way to Trizact A6. I only differed from my usual sharpening procedure in one way – I used fresh belts, instead of old ones. Normally for sharpening, I am using old belts because sharpening is extremely rough on the belt and destroys it very quickly.

The measuring method is wildly imprecise – the testing thread is not homogenous, the angle at which I put the blade on it is not always precise, I do not always hit the center, I am not pushing with constant speed, the kitchen scales do not renew the measured value with sufficient frequency and probably several other variables. I have experience with such measurements from my previous job though and there are ways to get relatively reliable, reproducible, and usable results even so. One of those ways is to make lots of measurements – that is why I took 12 measurements, discarding two of the most egregious outliers and making the evaluation with the remaining 10. There are mathematical methods for discarding outliers but for my personal purposes, the Lookandsee method suffices. (Thirty or fifty measurements would be better, but I am not going for exact values for individual grits, I am going for a comparative assessment between those grits. Anyway, not going to write a boring lesson about measuring).

Here is the boxplot of those ten measurements per each grit:

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And it looks like my prediction from yesterday was bang-on. Which is satisfying to my ego, but also boring in a way. It would be much more exciting if it were different.

What you see here is the cutting force going rapidly down from ~270 g at 180 grit to ~ 75 at 400 grit. At this point, the blade is capable of cutting freely hanging paper. Then it falls some more to ~40g  at 800 grit and more or less stays there till the end (the knife is shaving-sharp at these stages). The slight increase at 1200 is a fluke that would most probably go away if I have made more measurements and/or invested time and resources in refining the method. I made ANOVA test and there is no statistically significant difference between the last three fine grits.

So in conclusion, sharpening knives beyond 1000 grit indeed appears to have very little practical value. At 800 grit the blade is already shaving-sharp and polishing the edge further only costs more time without noticeably improving its cutting capabilities. With more precise measuring method there might be a difference, but it would be very, very tiny. I think that I can replace the last two belts with a leather belt infused with stropping compound and get the same result. And since time is money, I will do exactly that.

Sciencing Sharpness – Part 1 – Predictions

I hope to use my new sharpmeter to get some knowledge about, well, sharpness. And since I am going to be playing at science whilst doing so, I have decided that I will write down the predictions for my tests. The tests will not be blind, because I will be doing both the sharpening and testing and there will still be some subjectivity to these tests, but nothing is perfect. I am doing these tests to gain some knowledge and I will share that knowledge for free but there will inevitably be bias.

The first test that I intend to perform is the influence of grit on edge sharpness. I think that after establishing the bevel with 180 grit the cutting force will go down significantly with the next steps, but it stops changing significantly above 400 grit. My reasoning for this is the fact that it is possible to get a knife shaving-sharp with ca 320 grit stone and at 320-400 grit usually the wire edge/burr falls off. I think that I have mentioned in the past in comments somewhere – either in Marcus’s place or here – that going above 1000 grit in sharpening makes little sense function-wise, although I cannot find the comment now. I will go up all the way to trizact A6 belt (the equivalent of 2000-2500 grit) in the experiment.

The second test that I intend to take is the influence of the sharpening angle. There was a heated debate between me and Marcus on this issue a while back -click-  and I really want to test it (caveat from the first paragraph applies doubly). I expect the force needed to cut the thread to rise exponentially, i.e. slowly from 10-25°, then some more for 30° and even more for 40° and again even more for 45°. I won’t test sharpening angles steeper than 45° because it makes no sense IMO since a 45° sharpening angle means a 90° edge. I know from praxis that knives sharpened at 15°, 20°, and 25° can be shaving-sharp. I do not know much about the 30° angle, since that is extreme and I only sharpen hatchets and axes at that angle and I never even tried to get those to shaving-sharp. They do cut paper though.

So, sometime this week I shall heat the workshop again, sharpen some steel offcuts (probably pieces of old hacksaws) and go measuring.


It is freezing here and I still do not have the slightest inclination to do something useful. But I need to heat the workshop occasionally to prevent it from completely freezing. Not that it would be super bad, except that maybe ice forming in the cooling receptacle near the grinder could damage it. Anyhoo, yesterday was a workshop heating day. I could not do anything super useful – it took me hours to raise the temperature to a bearable level and soon after I stopped feeding the stove, the temperature got down quickly again. But I could use the time to do something small and simple so I have made a device for measuring knife sharpness (I did not invent the concept, I saw the principle somewhere on the interwebs sometime ago).

© Charly, all rights reserved. Click for full size

It is simple and consists of two main parts. One part is a board with four legs and a 35 mm hole in the middle. A tiny table that can be put over my kitchen scales.

© Charly, all rights reserved. Click for full size

The second part is a small wooden cylinder with a cutout and two screws on each side of it.

© Charly, all rights reserved. Click for full size

I can span a thin thread between the two screws and when the cylinder is put on the scale through the hole in the middle of the tiny table, I can cut the thread safely for me, the scale, and the furniture.

The main downside is that my kitchen scale does not have a “Hold” or “Max” function so the measured values are not super precise. Another problem is the used thread – a very thin fishing line would be probably better since this one has a tendency to get damaged during spanning. Or perhaps a very thin copper wire – I might try to extract some strands from leftovers from speaker or ethernet cables. But when being very careful with spanning the thread and doing the cut slowly and carefully, the setup gives useable results and I did learn some things.

Here is a boxplot of 10 measurements with the three cutting implements in the photos – a fresh razor blade, a paper-cutting-but-not-shaving-sharp sharp knife, and a blunt table knife (I used the non-serrated part which is about 1 mm thick),

© Charly, all rights reserved. Click for full size

The razor had an average cutting force of ~6 g, the sharp-ish knife ~60 g, and the blunt knife ~ 1000 g. The less sharp the blade the bigger the spread but even with sometimes ridiculous outliers, there is a definitive and statistically significant difference between these three and it does give me some information and opens future opportunities. I would like for example to examine the relationship between sharpness and sharpening angle, to get some hard data to back up my opinion that anything between 10-30° works just fine. My prediction is that the relationship is not linear and as the angle gets steeper, the cutting ability gets exponentially worse.

I did learn one thing – my “Not a Masterpiece” was sharpened at a 20° angle and the only knife that actually scares me – the bigger knife from the two-knife applewood set – was sharpened at 15°, yet both measured within the same range as the razor. Although the applewood knife completely failed to register on the scale one time, thus my suspicion that it is the sharpest knife I made so far might be true.

Of course this only tests edge geometry, not blade geometry. I could use a similar setup to test the influence of blade geometry on cutting force too, but I do not have a reliable medium to do so yet. All things that I have thought of so far are either expensive (cork, rubber, silicone) or have highly inconsistent properties (fruit & veggies). But maybe I will think of something to test blade gomtry too.

Women Crafter on Youtube – Knitter – Engineering Knits

My mother used to knit and we still have two straight knitting machines of a solid metal build. I did learn how to knit as a child but I already forgot it all and it is unlikely that I will ever need it. My mother-made sweaters have served me well for years by now and I expect them to continue to serve well for enough years to not need a replacement.

She has also knitted several pairs of thick socks that come in handy on winter travels when I need to sleep in some poorly heated room. Or when the winter is so cold that despite heating, sitting at the PC gives me cold feet. But we do not have a circular knitting machine, all the socks she has made had to be made by hand. Thus I have enjoyed watching a circular knitting machine in action because that was the first time I saw it.

Pity the machine seems to be made of cheap 3D printed plastic. It won’t have the durability that my mother’s knitting machines have – those are still fully functional after decades of intensive use.

If you are interested in knitting and its history, Engineering Knits has a lot of videos on that topic.

Jewellery meets Art: Hokusai’s Great Wave off Kanagawa

Hokusai’s Great Wave off Kanagawa is one of my all times favourite pictures. The churning water, the two tiny boats struggling in the waves, Mount Fuji in the background, almost an afterthought.

IHokusai's famous print showing a wave crashing down on two boats.

Source: Wikimedia

Also, it is blue. In short, a perfect image to use for trying an image transfer on polymer clay. If you have a laser printer, image transfers are pretty straight forward: print, put upside down on clay, add nail polish remover to the back, wait. Trying this with my cheap toner wasn’t very satisfactory, though. The printouts are always rather pale, and since only part of the toner transfers, the result on clay was visible, but not brilliant. I dared to add two tiny versions of the image to a bunch of things I had to print at work anyway and tried again, this time with high quality print outs. The results were much better, but still not as brilliant as I would have liked. But since I never found a crafting problem I didn’t want to beat into submission, I decided to use the first weak transfer clay and paint in the details with acrylic paint, and while I’m not usually good at painting, I’m quite happy with the results:

Round earrings showingt the crashing wave

©Giliell, all rights reserved

Yes, of course I forgot to mirror the image. Both times. But I love how this has a look like ceramics now.

And here’s the version made from the quality printout:

Round earrings showing the central wave in great detail but mute colours

©Giliell, all rights reserved

You can see that it’s lacking contrast and brilliance, even though it is rich in detail. I’m thinking about using the transfer plus acylics method with other paintings as well, I think van Gogh would be a good candidate for these projects.