This Was Not Supposed to Happen – Quality Control and Salvage

The last batch of knives did come out of quench straight-ish, but the tangs were a bit crooked on some blades. No biggie, he said. Those are not hardened, he said. Will be corrected in a jiffy, he said. And then he broke a blade in half because he was an idiot.

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Still, I do not think the blade should have broken like this, it is tempered and I did not exert too much force. But maybe I did. Unfortunately, the tangs did partially harden on some blades, which is a major headache because I have to heat them up significantly in order to straighten them now. As my hardening experiment has shown, with this steel all that is supposed to be soft must not be heated above the 1050°C at any point in the process. Which, admittedly, I did not know for sure at the time of quenching these blades.

So what to do with this? I have spent nearly eighteen years being involved in quality control in one way or another, and I must say it is a great way to make enemies at all levels. Customers hate you for the crap your colleagues have produced, your colleagues hate you because you point out to them that they have produced crap and the management hates you because you cost them money (both when things go well as well when things go awry) without generating any profit whatsoever. And everybody expects you to tell them how they should solve the problems you found – despite that part being actually their job, with yours only being the pointing out of the problems.

Now I am my own quality control so at least now it really is my job to solve the occurring problems. For example, apart from this broken blade, one blade seemed to be softer near the tang. I have decided to continue work on it anyway and I established later on that it was only slight decarburization and the steel is sufficiently hard deeper under the surface. So far so good. But is there anything that can be done with this broken blade? Well, I surmised that yes, and I have decided to try some new things whilst doing it.

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The broken-off tip was long enough for me to grind small (9 cm) blade out of it with enough steel left for a short hidden tang. I have simply cut it with an angle grinder to the desired shape and then thinned, formed, and polished the blade on the belt grinder. The notches on the tang are there to allow for the epoxy to grab onto.

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I have made the handle from a piece of apple-root from a dead tree given to me by my neighbor. The bolster is from a coconut shell. The wood was partially rotten, so I have decided to try my hand at a new thing – stabilizing the wood with epoxy resin. And to utilize my resources meaningfully on this experiment, I went and cut some more wood, even more rotten, from a willow trunk that lay in the garden for years. It is full of holes, wood dust (AKA grub poop), fungal discolorations and it is extremely porous, it even crumbles in parts.

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I do not have a compressor or a proper vacuum pump, and I was unwilling to spend any money on them at this stage, the resin itself was pricey enough. So I tried my best with things I already have at hand and I came up with this.

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These are two huge thick-walled glass jars for canned fruit, with removable snap-on covers. They should withstand vacuum reasonably well. I have replaced the glass-covers with ones made from particleboard, with the joint and snap-on latch made from fencing wire around some screws.

The jar on the left has a ball-valve in the middle, with 6 mm tubing attached to it. The jar on the right has two 35 mm holes and one 6 mm hole in the middle. To the middle hole is attached the thin tube from the left jar, shop-vac is connected to one of the big holes and a swiveling cover is over the second hole.

I have given the knife with handle suspended in resin in the left jar. When the shop-vac was running with the ball-valve open and the big hole covered, it sucked air reasonably well out of both jars. But shop-vac cannot run with blocked intake for too long, thus the ball valve and the covered hole – after half a minute I could close the valve (keeping the low pressure for a few moments more), opened the big hole and left the shop-vac cool with flowing air for a minute or two. Then I have repeated this process as many times as it took until no bubbles were rising from the resin.

To get an estimate, I weighed the knife before and after, and it has gained about 20 g of weight (65 to 85 g), which seems reasonable, the wood was not extremely rotten, only slightly so. I have also weighed one of the willow pieces and the weight gain there was much more extreme – from ca 20g to 120 g. I have not cut the wood to see how deep the resin has penetrated, but it definitively penetrated deep enough to work on pre-formed handles, even if not on squared wood.

So this has confirmed that I can do this with the equipment I already have and that investing in some better equipment is thus warranted. Still, I am hesitant about spending 100,-€ or more on a vacuum pump, I hope I can mc-gyver something a lot cheaper. On Wednesday I am going shopping for parts. If I succeed, I will let you know.

Oh, and here is the finished knife.

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Overall length 20 cm, blade length 9 cm at the spine, 3,5 cm wide, satin finish (trizact A100). The handle was polished to 1200 grit and buffed with beeswax.

I have given the knife to my neighbor because she has refused payment for the dead tree and I think she should get something for such beautiful wood. She did not object this time and I hope it will serve her well.

Different Hardening Methods for N690 – Experiment

When I was hardening the blades two days ago, I have tossed in there six cut-offs as well and I have used different methods to quench them. After that I had still one piece left so I have heated that up to the 1050 °C and let it cool in the forge. Then I performed some tests and the results are very interesting.

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These are the samples and methods used (marked by the number of notches on the edge):

0 – left to cool in the forge
1 – untreated
2 – left to cool in the air
3 – quenched between Al plates only
4 – oil
5 – water
6 – AL plates + water + Freezer fro 2 hours

None of the samples were subsequently tempered, so they should be at peak hardness.

With the sample size just 1 piece per method I cannot of course perform too many tests. The idea was to polish the samples – which I did. And already during the polishing, I have noticed that all samples seem to be hardened, except #1.

The next step was supposed to be to etch the surface and look at the structure under a microscope. Well, that did not work at all, and the reasons are a mystery to me. Just as it happened with the knives last time, it happened again here – the electrochemical method worked on some samples perfectly, but completely failed on others. I was unable to solve the problem. Another thing was that my microscope apparently does not have big enough magnification to see a difference between the original steel and the quenched one. I could re-build it and improve it about ten times, but I am still not sure if that would be enough and I do not want to get sidetracked to that now, it would be probably more than one day of work and I have already spent two days having fun instead of working.

So I did what I could with samples of this geometry. First trying to scratch them with my hardness measuring gages .

The sample # 1 could be scratched by the lowest 38 HRC gage, which was to be expected.

All samples except # 1 could not be scratched by the 62 HRC gage, so they are at hardness 62 HRC or more. Which is something I did not expect, especially not of # 0, which was left to cool in the forge – and that took definitively several hours. I was expecting this sample to be harder than the new steel, but not hard enough for a knife – but it evidently is more than enough hard for a knife, hardness 62 is in fact quite excessive.

Secondly, I have tried scratching the samples against each other, and the results became even more interesting. All samples could scratch # 1, as expected. But none could scratch #4 and #4 did scratch all, whilst the remaining five could not scratch each other, so they are all of the same hardness.

Thirdly I have put the sharpest angle of the triangle approx 10 mm into a vise and break it off. #1 has bent easily, as expected, all others have snapped off.

What can I deduce from this? Several things.

  1. Sample #4 was hardened with the method recommended by the manufacturer and did come out as the hardest of them all, possibly somewhere around 63-65 HRC, which is as hard as steel can get. It could be a fluke (remember – sample size 1), but it could be the reason why this method of hardening is recommended. It is not surprising.
  2. From a practical standpoint, the method of quenching seems to be quite inconsequential nevertheless. The oil quenched sample would be brought down a few points in heat treatment anyway and for practical purposes, anything above 51 HRC will be usable with just a bit more edge maintenance, anything above 55 HRC will have reasonable edge retention and above 57 HRC we are in the realm of no reason to complain whatsoever. In this light, the difference between the recommended oil quench and all the other methods seems to be so small as to be trivial and only interesting from a nerd standpoint.
  3. The freezer step does not seem to have done anything for this one piece, but this does not rule it out from use on larger pieces that could not be so thoroughly and consistently heated in my setup. Did not do any harm either.
  4. Although tempering was not tested, this experiment does indicate that it is just not possible to really destroy the edge on this steel by overheating it during grinding/polishing since even cooling it from the 1050°C to room temperature over the course of several hours hardened it very nearly as well as the recommended oil quenching. I will not test tempering temperatures with regard to this specifically since there are graphs to be found on the internet that show already that the hardness of N690 does not get below 56 HRC up to 900°C.
  5. If I want to peen the end of the tang, or do any other work with it, I must be careful to not heat it above the critical temperature at any point in the process. Because once heated above certain threshold, this steel hardens, I cannot prevent it and I probably cannot anneal it again.

It would be interesting to see what is the exact influence on toughness/strength once tempered. I could not find it, so I will have to test it myself. But for that, I will need another sample geometry. So maybe next time.

All in all, the N690 seems to be pretty remarkable steel. It does not have the label (and price tag, otherwise I could not use it) of “super steel”, but it is no wimp either and apparently is not very fussy about the heat treatment, apart from the requirement to heat it above 1050°C.

Quenching Jig

I hope you are not bored with my writing about knife making yet. It is not that I do not care about other things, but knife making is where most of my focus is right now. And this week I had barely the strength to do anything else at all.

I have started a new batch of blades, 18 pieces altogether – 4 small hunting knives, 4 badger knives, 5 chef knives (prototyping new design), and 5 universal kitchen knives. So this whole week I was drilling, cutting, and grinding steel every day. I have progressed reasonably fast, despite being also slow. Because I simply cannot handle more than 6 hours net a day at the grinder, and I have to make a substantial pause every two hours. My hands are doing reasonably OK and I have been pain-free for a few months by now (despite never having a diagnosis about what was wrong last year), but even so, the vibrations are a strain on the fingers. And after two hours not only the glasses start getting foggy – the mind does so as well and thus the risk of injury increases.

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Today was a big finale of that busy week and all knives went into quench and tempering. This time I have decided to use quenching foil on all blades, despite bad experience on some blades the last time. I have decided to do so because the protective coating that I have concocted did work well but also was a real pain in the ass to remove afterward. And that did cost me a lot of time and I destroyed two belts before I figured it out. But I have tried plate quench with on this steel with moderate success), and I have hoped, really, really hoped, that doing plate quench on newly ground and straight blanks will lead to straight blades without having to scrub off a hard crust.

And following the maxim of Scrooge McDuck “Work smarter, not harder”, I have done my best to make the plate quench easy and reliable – I have built myself a jig. The construction is very simple and it did only take me a few hours.  I have used the locking pliers and aluminum plates from last time, but I have connected it all into one piece that can be easily used in one hand. So instead of one hinge in the middle of the plates, I have added two hinges on the sides. Then I have drilled holes in the fixed jaw of the pliers (and re-ground it a bit) so I can screw one of the plates to it with two M4 screws. The movable jaw is not fixed to the second plate, but it does fit into a groove cut in it and it was also re-ground for a better fit at the angle where most blades will be gripped.

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© Charly, all rights reserved. Click for full size

The idea was that I will hold this jig in my left hand, with my right hand I pull a blade out of the forge, insert it between the plates (still in the foil), lock the pliers and dunk the whole thing into a bucket of water. And it worked well! None of the knives came out of the quench with a perm or as a banana-imitation, none have cracked either, at least I did not notice it yet. All but one blade quenched properly (and that one I have re-quenched OK the second time) with hardness above 55 HRC, most even over 62.

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© Charly, all rights reserved. Click for full size

Hardening all these blades took me only 15-16 minutes per blade, so even with all that foil wrapping, I was well within a reasonable time. There was only one small problem towards the end – my new burner worked really well and I have reached and held 1.050-1.080°C without problem with four blades in the forge, but after a few hours, it started to struggle. I thought at first that I am running out of propane, but that was not the case. As it turns out, the propane bottle got too cold (just 10°C) after that long continuous decompression, and the gas was evaporating less. I am not sure yet how to solve that problem for the future.

Now the blades are in the second tempering cycle (each cycle two hours at circa 180°C) and they did not seem to develop any bends or curls in the oven either. So far, so good, let us hope it stays that way since I am going to try some new techniques with this project again.


Project Badgermascus – Part 12 – The Final Badgering

The knife is finished, although not sharpened, and here are the final pictures. I am going to make more knives of this design because I think it is a good knife for forest walks, especially mushroom hunts. And I am naming the design “Badger”.

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The overall length in the sheath is 205 mm. The sheath is from vegetable-tanned leather, carved (badger paw print, frame edge), stamped (leather weave, edge trimmings) and dyed, thoroughly infused with beeswax, oiled with olive oil on the inside and buffed with dubbin outside.

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The sheath has a metal belt clip. This allows the knife to be worn not only on the belt but also clipped onto/into the pocket or boot. The pommel sticks out of the sheath far enough for a comfortable grip with index finger and thumb when pulling the knife out. The knife clicks into the hardened leather firmly enough to not fall out of it with its own weight, but can still be pulled out comfortably.

Stitching is made with a two-needle saddle stitch with artificial sinew. The end knots are melted together and hidden.

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Brass fittings have a black patina with clear brass badger paw-prints over the pins. Scales are from naturally aged cow bone, slightly larger than the tang and wider than the brass fittings. The right scale is adorned with scrimshaw engraving of a badger head – this is a new skill that I had to learn but kept secret since I had no guarantee it will work out. I think it did work out OK. I may add a bit more pigment once this hardens, but maybe not, I like it the way it is. The badger is colored black with coal dust, the patterns, and the frame, with ochre (rust).

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Handle length 100 mm, drop-point style blade 87 mm length, 3 mm thick at the ricasso. Point of balance just behind the first two pins in the handle scales, also between the index finger and middle finger. It feels a bit handle-heavy but nimble. The steel has dark-grey patina from an oak bark extract.

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The left side of the handle is unadorned except a few scratch grids around the pins. The left side of the blade has significantly different steel pattern due to how the san-mai was hammered at the Badger Forge.

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Back of the tang has a row-of-crumpled-leaves fileworks, the belly has a simple triangle pattern.

Overall, I am satisfied with my work here. There are things that I am critical of, there are things that I definitively might have done better – it is not a masterpiece yet, but I think I am getting there. I have learned a lot again and many of the things that took me several days this time should be just a day or even less the next time (the leatherwork for example).

Project Badgermascus – Part 11 – Stitch This!

The day before yesterday I had to make the leatherwork all anew, because I spilled some glue on the forefront of the sheath and it has proven to be irreparable damage, it completely ruined the leather. So I have made a new piece, this being, therefore, the fifth attempt. And when I was at it, I have improved my tools to make a better job.

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I have re-filed the basket-weave stamp to make it crisper and bite more deeply. That has allowed me to better feel the position of the stamp when moving it along the edge and positioning it in the next point on the pattern grid. I have also used a straight edge and I scribbled a faint line for each row before stamping along it.

To get the dye better into the tips of the claw marks I have needed a very fine brush, so I had to make one. And since I do not have any weasel hair, I have used a few strands from a goose feather. It has worked perfectly.

This is my first attempt at a sheath with a metal belt clip. I have first riveted the belt clip to a piece of leather and then glued/stitched that piece of leather onto the sheath. Only then have I glued and stitched the rest of the sheath together. This avoids any contact between the knife and the metal of the clip and secures the clip very firmly in place.

For making the holes I have used 2 mm drill bit in my drill press since I found that to be by far the most convenient method. For stitching, I have used saddle stitch, and I hope I have used it correctly. I had trouble finding a comprehensive tutorial on how it is done.

BTW, holding the work between my knees is really uncomfortable, I will have to make myself a proper tool for this. So many tools that I still need… Anyway, back to the stitching.

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Saddle stitching is made with two needles and here you can see how I do it. First I am pulling the right needle through the hole all the way to the end (top). Then I put the left needle in the hole whilst wrapping the thread from the right needle around it in a loop (middle). When carefully pulling the left needle through the hole (taking care to not stitch through the thread already inside) it creates a knot that gets tightened inside the hole when both threads are pulled to the limit (low). This kind of stitching is very strong and it does not unravel even when the thread is worn/cut/breaks in one spot.

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The almost last step in making the sheath was wet forming. I have put the whole sheath into lukewarm water and let it soak in there as long as bubbles were coming out of it. When it was all soft and pliable, I have wrapped the knife in food wrapping foil, put it in the sheath and formed it around it simply by finger pressure until it had a shape that I wanted. I have used clamps too, but only for a few minutes around the edge, I did not leave in clamps until it was fully dried, it was not necessary. In fact, to let it dry I have simply hung it on a window handle as you can see in the picture.

Today was the final day of this project. I did make some minor mistakes when making the sheath, so I had to glue a little wedge of leather inside with five-minute epoxy, but that is simply a lesson learned for the future and not something to worry about aesthetically or functionally. I must simply remember next time to make the blade portion shorter (and slimmer) and the handle portion longer. But it was working just fine, the knife holds in it strong enough to not fall out, but it can still be pulled out with just two fingers by the pommel. So I have infused it with beeswax and dubbin*, so it is hard almost like plastic, but still with a pleasantly natural and organic feel to it. That made it a lot darker and I applied some black patina too to make it look a bit aged, to fit the knife.

So, after a month of procrastination interspersed with bouts of hectic work and attempts at learning new skills, at least one piece of steel out of three has made it into a final product. I am going to try and make some nice pictures and tomorrow I will post them.

  • The dubbin that I have made almost two years ago and which I stored at room temperature the whole time did not go rancid or moldy or bad in any noticeable way, and the leather on the products I used it on did not degrade in that time either.


Project Badgermascus – Part 10 – Leather, Stomping, Dying…

Well, I did not stomp out of the room in rage nor did I die of exasperation, but I must say the leather stamping did not go as well as I would wish. Despite making three mock-up sheaths from crappy leather upfront and practicing on several more leather off-cuts, I have messed-up the basket-weave stamping bigly. I do not know why. Maybe the stamp is crap, maybe it is the slight deformations of the leather that happen during work due to the stamps, but the end result is a bit chewed-up in places because I did not position the stamp correctly and I had to redo that spot several times. I have resigned that I cannot do better and decided to not give it another go.

So unless I mess up at some following step and have to start all over again, this is the final design.

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The wooden mallet did help a lot, allowing me much better control of the strength with which I hit, so that at least worked out well. The burnisher worked like a charm on edges too.

Carving the badger paw-print was a bit of a challenge, but I think I got it acceptably on this final piece. Working with a swivel knife is interesting and it takes some getting-used-to, especially on tight curves, but it did seem fairly intuitive to me (mind you, I only did these simple designs). The home-made beveler for the fingerprints worked well too, I have no complaints there.

I have colored the mock-ups with three different color schemes and what you see here on the final piece is what my mother has assessed as the best combination. In case it went south, I had a secret backup plan, called “Operation: Full Black”. But the dyeing did not go south so far, I made no blotches in the light patches, there are no streaks or shadows when it is all dry and no bleeding over the borderlines either. The claw prints are not ideal, but I can live with that.

Tomorrow is gluing, stitching and wet-forming time. This is only a second sheath of this construction that I make – and first with a belt-clip – so there are no guarantees as to the result.

Edit: Publishing this did not go well. Butterfingers.

Project Badgermascus – Interlude 5 – Making New Tools, Learning New Skills

I tried to make two sheaths out of crappy leather first, and it is a good thing that I did, because not only the measurements did not fit the first time, but the stamping and carving were not very good either. Who woulda thunk that making the basketweave pattern is a lot harder than YouTube videos made by master craftsmen make it look like?

The second time I got actually better, but I think I will make a third one before going to the good leather for the final product. Although I did cut a piece of good leather for experiments too and it does work differently (better) than the old crappy one.

In due course, I have made several new tools.

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I had to make myself several new tools because those that I bought did not cover all I needed. I want to make a basket weave pattern on part of the sheath, but the store where I bought the rest had none and on other stores, I could not find one that I liked. Also, the beveler was a bit too big for some of the works that I need to do and the set lacked a mule foot tool, so I made one of that too although I do not intend to use it right now.

I have made all this using a hammer to drive the stamps, and that turned out to be not optimal. Apart from mushrooming of the tool ends and flaking off of the chrome-plating, I thought that the hammer hits unnecessarily hard. So I took out my lathe and started to make a mallet.

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I took an old furniture leg from beech wood for this, although it is not optimal. It is hardwood, but not nearly hard enough. I will probably have to replace this soon as it gets chewed up fairly quickly, but it should last at least for one project. I have already an idea of how to make a new, better one with replaceable head, but that will have to wait for now – for that I first have to find out if I can buy or find suitable materials. If not, I will either try to find or glue-up a big enough piece of jatoba or black locust, since those are a lot harder and thus can withstand more abuse.

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And since building the lathe for just one thing is not worth the hassle, and I need to learn lathe work anyway, I have also taken another furniture leg and turned myself a burnishing tool, from beech wood too. Sycamore, black elder, or cherry would be better for this (they have smaller pores and are more homogenous), but I did not have a suitable piece of any of those quickly available, and this should suffice. Next time I have the lathe on the table, I will probably make a burnishing wheel for the drill press, but with the amount of leatherwork I am currently doing, this is enough. I soaked the mallet and the burnisher in boiled linseed oil and they are drying now. One cover should suffice, so tomorrow they should be ready to use, at least the mallet. The burnisher won’t be needed for a few days yet.


Project Badgermascus – Interlude 4 – New Tools

I have decided to make a sheath for the knife, but since the blade and the fittings are quite fancy, a plain leather sheath would be unbefitting. So the time has come for me to learn some fancy leatherwork. As you know, I am quite fond of making my own tools, but this time around I have decided to bite the bullet and buy some basic stuff for starters.

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These are really just the basics – a swivel knife and six basic stamps, a beveler, and a groover. The cheapest ones there were to find.

I will surely make some of my own tools in the future, but these should, hopefully, suffice for a start. They do not allow me to make anything that cannot be done with the tools that I already have – but they allow me to make those works much easier, more consistently, precisely and quicker.

Now I am going to cut up an old leather handbag and test some design ideas.

Project Badgermascus – Part 9 – Almost Done

The knife is done about 95% now. I have peened and ground flush all the pins on scales without some major failure, although there did appear one tiny crack near one of the pins ‘sigh’. I have sealed the crack with super glue and sanded it over, there is nothing else that can be done about it.

I did not do a very good job at the pins, I must say. I think the mistake that I make is leaving myself way too much material to move, which leads to a lot of problems later on. I must remember that for 3 mm pin it is quite enough to peen less than 1 mm material into a recess just 0,5 mm deep. It is not as if the pins need to hold extra-strongly.

But, it is done and it is what it is. I applied a little bit of patina to the pins. Not to make them black, just to make them ever so slightly aged. Funnily enough, the patina has highlighted some of the imperfections – and that made the whole assembly to look actually better. Only you must forgive me for now for not revealing the whole knife yet. There is still a lot of work to do before I consider it publication-worthy, do not expect that very soon.

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I am thinking now how to best seal the surfaces and the patina. Either beeswax, or drying oil. Or both. Any suggestions? I have zero experience with patina on metal jewelry, which essentialy is what this is.

Project Badgermascus – Part 8 – To Peen or Not to Peen…

Today was very stressful, although I did not, in fact, do too much work. But I was agitated about it so I procrastinated a lot, putting off each step for fear of mangling the work and losing a lot of progress. That will also be the case tomorrow.

Today was the day of gluing the scales to the tang. And because I wanted to peen the pins from the beginning, I also had to prepare for that.

For I lack proper ball-peen hammer for this kind of job. I have a wide variety of cross-peen hammers, but only one, big, ball-peen hammer. And that is way too big and chunky for 3 mm brass pins. They are not sold in any stone shop around here, and ordering one online would again put me in the age-old problem – is it worth buying something if the shipping costs more than the product?

So I have to make do with my smallest cross-peen hammer and a few thingamajigs that I have made myself to make the job easier and, hopefully, better.

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Peening pins in bone is kinda dangerous. Bone is hard, but not particularly strong and it can easily split. To try and reduce the risk of splitting I have therefore pre-peened one side of each pin before assembly, so the pins are shorter and thus less likely to bend when I am peening the other side. To make a better job of this I have taken a piece of mild steel from a failed attempt at burner diffuser and I drilled in it 3 mm hole, chamfered to about 5 mm recess on one side. Then I held the pins in a vice and peened one end into this recess.

The second tool that I have made is from an old hook-nail. It is very old and therefore good medium carbon steel, hardenable, although not to the highest degree, and very tough. If the tool works, I am going to carburize the surface and quench it.

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First I have cut off the hook and the tip. Then I have center-punched the center of the square where the tip used to be and dished it out first with a 3 mm bit and then 7 mm bit in a hand-held cordless drill. Then I put a big diameter ball burr for die-grinder into the drill and rounded the inside of the dish and I ground the edges round with a file. I have tried it and it seems to work well when used after the hammer for the final touches on the edges. So I hope to get nice round peened pins tomorrow.

With that done, I have also repaired one of the scales – two holes were a few tenths of a millimeter off so I could not put the pins comfortably through all holes. Not a big problem, I have filled the two holes with quick-curing epoxy mixed with bone dust and drilled them new. You would not notice there was a mistake there if I did not tell you about it.

Then I was ready for the job that I was putting off – the glue-up.

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I have used slow curing epoxy, with work-time 1,5 hours, instead of the 10-minute one that I have used previously for kitchen knives. The reason for this was not only to reduce stress and the possibility of a complete fuck-up, but also the fact that this simply could not be done quickly. Mixing the epoxy, slathering it over the tang and attaching the pins and the scales was simple enough, but after that came the difficult part – to clean all the squeezed-out epoxy from the fileworks. I have used first small pieces of kitchen towels soaked up in denatured alcohol to wipe out the biggest excesses and then a toothbrush soaked in the same to tease-out glue from al the nooks and crannies. I do hope I have made a good job because there is no way back now except either take it as it is or to drill out the pins, smash and grind out the bone and start with the handle scales all over again, which would not be fun at all.

Project Badgermascus – Part 7 – The Pinkening

For the next attempt at the patina, I had to think of a more fool-proof way to mask the areas of the assembly that are not allowed to come in contact with the chemical solution. I have used plastic packaging tape in the past, so I tried it this time. But the one I bought this time is extremely difficult to take off because the glue is too strong. That makes it also difficult to apply tightly around the blade since once it gets stuck, it cannot be corrected. And, the masking around the filework was a major headache-inducer, there the tape was totally insufficient.

So I needed something that is resistant to water and water-soluble chemicals both acidic and basic, hot and cold, something that will show me clearly what is masked and what is not, something that can be applied with high precision and good adhesion to complex surfaces and simultaneously can be removed easily later on without damaging the patina.

And after some thinking, I did come with a solution that worked really well. I made everything pink!

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That is the cheapest nail varnish that I have seen at the local drugstore (2,-€ per bottle). Afterward, I have added the packing tape on big surfaces, but I think it was unnecessary and just me being overcautious.

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I proceeded to make the patina on brass fittings by alternating between acid bath (HCl, very diluted) and polysulfate bath (with occasional brushing with a soft brush under running water) until I have received a color that I was content with, which is sort of metallic blue/brown/dark gray, very similar shade to the oak-tannin patina on steel.

Cleaning off the varnish was a bit of a hassle and used up a lot of paper towels and acetone, but the important bit is that it could be done, could be done well (it was easy to spot uncleaned places) and did not scratch the patina on either the fittings or the blade. I will probably buy heaps of cheap nail varnish, it opens up great possibilities.

Project Badgermascus – Part 6 – Trials and Tribulations

I have spent both Monday and Tuesday finishing flattening, drilling, and fitting the handle scales and the brass fittings.

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First I have sieved some bone dust that I have collected through a fine nylon mesh (from pantyhose – I do not wear them, but they can be quite useful in the workshop, so I have indeed several in a drawer). I mixed then the bone dust with five-minute epoxy, filled the hollow back of the bones with it and heated it with a heat gun to about 70°C (not so hot you cannot touch it, but hot enough you cannot press your hand against it for a longer time, a hairdryer would suffice too for this particular task) for quicker curing and stronger bond.

After it completely hardened I ground the back flat again and proceeded to drill the holes for pins.

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Drilling the holes was relatively uneventful. Double-sided tape was very useful in holding the scale on the tang and the whole assembly on a flat piece of wood for drilling to avoid chipping of the bone on exit. Also, I have used blunted and overheated drill bits to hold the scales in place for a good fit and I did not mess up the job terribly. I did make minor mistakes on the left handle scale, but those should be correctable when fixing everything together.

With the scales drilled and fitted against the bolster, I proceeded to make the brass pommel fittings. That went really well, and everything went smoothly. Too smoothly you might say. I glued the brass fittings in place, peened the pins and ground, and polished them over.

That is where the problems started, and I must say – they are not all my fault.

The first problem was that the round stock I have used for pins apparently has different chemical composition than the flat profile used for fittings. Had I known this, I would not file them flush and I would leave them slightly proud of the surface (“admitted” instead of “hidden”). However, there was no way back once I ground them flush, so I was hoping they will get hidden under the patina.

But the patining did not go well too, in three ways.

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The first  – I have made a mistake – I have not masked the steel properly. I thought I did, but I just did not. And as one Czech rather rude but astute saying goes – ” myslet znamená hovno vědět” – “to think (assume/mean/guess) means to know shit-all”. So when I was giving the brass a nice hot bath to copper plate it, some of that bath leaked under the masking and copper-plated and etched the blade in some places too.

The second – the different brasses did not take copper plating identically, it was a lot more difficult to copper plate the pins than the rest. It took over an hour to do on the pins what took mere minutes on the rest (which exacerbated the problem with poor masking later on).

The third – when blackening, I have made the solution probably way too concentrated. It has covered the parts in a nice jet-black matt color almost instantly. But that color has completely rubbed off when I washed it with water and brush. I did not realize the true cause of this so I tried it two more times, but it just did not take, especially not on the pins, After the third attempt I thought I am done on the pommel at least, but it flaked off the next day again.

These mistakes are not catastrophic, but they are a major setback. I had to re-polish everything (done), re-etch with ferric chloride (done), give the steel new tannic-acid patina (in progress), and only after that is done to my satisfaction, can I again try to patina the brass.

However, I have to deal somehow with the pins now. They are ground flush already, but since they will not take the patina the same way the rest does, I must leave them visible. And that means probably leaving them polished and not applying patina to them at all. I will do that and then I will decide whether I like it or not. If not, then I will have to drill them out and either replace them or, if I bungle that job (which is very likely) to make completely new fittings. Either way, it is at least one day, and possibly several days, of work before I can progress further.

However, there did come one good thing out of this – I found two new recipes for black that do not require copper-plating the brass first. One requires hot-bath with ammonia (CuSO4+Na2CO3 – precipitates basic copper carbonate which after filtering and washing with water can be dissolved in hot water by adding ammonia), so it is a major stink and not exactly easy or quick. The second one works at room temperature but is rather caustic and dangerous to handle (HCl + potassium polysulfide). I will probably try the second one now, although I do not like very much working with caustic solutions, since my equipment, as you have seen, is not exactly suited for that kind of job.

Project Badgermascus – Part 5 – Handle Scales

Tomorrow you will get a break from this project, I promise. But today, the Great Flattening from yesterday has continued.

After some deliberations I have decided to try and go for fully blackened brass fittings. That means that the blade will be dark grey, and the fittings really, really dark gray. What kind of handle material should I use? Marcus has sent me a nice piece of stabilized spalted maple, but I do not think it is the right material for this project. Ditto, any of the dark woods that I have. I think the blade deserves the poshest material I have available – bone. I think it will provide a nice contrast to the dark metal.

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Which meant I first had to rough-cut the scales with a hacksaw, which is one hell of a job, let me tell you. Bandsaw or any electrical saw is a big no-no for cutting bone, this has to be done manually. Including pre-cutting he flat sides, before grinding them truly flat.

Thus I had to spend the whole working day with a respirator and my fingers are all sore now. Because the grinding had to be done manually too. Belt sander does work on bone, but it destroys belts way too quickly for my liking and as I learned in the past, these thin flat pieces would have a tendency to be dragged out of my grasp, increasing the risk of injury or bungled work. So flatstone+glue+sandpaper it was. Maybe after I build myself a disk-grinding attachment this work will be easier, but now it is not.

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The scales are ever so slightly bigger than the tang and thicker than the bolster now, and they will remain so. I do not intend for a flush fit, but for a proud one ( I have seen English-speaking knife-makers refer to it as “heirloom fit” although I was not able to find anything specific about it, so I am not sure that is the correct term).

The principle is the same in carpentry – whenever two surfaces join, you can make the joint either hidden or visible, but it should not be visible because you failed to hide it. So if you make it visible, it should be apparent that it was intentional. Like gluing in spacers, making the surfaces meet in a groove and not on a flat, etc.

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Today’s work ended in the kitchen, where the two rough-ground scales ended in a pot at 60°C for an hour or so with circa a teaspoon of washing soda and one spoon of washing powder in 1 l of water to dissolve and wash out as much of remaining fat as possible. In the end I have added a teaspoon of hydrogen peroxide to whiten the bones a bit, although complete whitening is not possible on these.

Tomorrow when they are dry I shall fill the hollows on the inside (where marrow used to be) with epoxy to make them flat. After that, I can start the remaining works, i.e. fit and polish the pommel, drill all the holes, and finally, the glue-up. We will see how that goes.