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User:Stever/Projects/rondeldagger: Difference between revisions
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As the original, being an archaeological find, was a little short on detail I decided to improvise a bit on the guard an pommel piece and take inspiration from other daggers from the same period to fill in detail where the original was lacking. These 2 sections were made from a sandwich of the same teak(probably) used for the hand-grip in between 2 sections of octagonal stainless steel with 8 rivets holding each sandwich together. Stainless steel obviously wouldn't have been available to the original makers but given that these sections are in contact with the hand when held, and I don't have servants to polish them every time someone touches them, stainless seemed a sensible choice!
The teak was cut on the [[Tools/tablesaw|table saw]] and then reduced to target thickness of 4mm using the [[Tools/planer|planer]] (very carefully, working with material that thin on it is rather hard!). The stainless steel was cut to approximate shape using the metal cutting blade on the [[Tools/bandsaw|band-saw]] and then mounted up in the [[Tools/boxford|boxford CNC milling machine]]. It turns out that stainless steel is quite challenging for the boxford to work with, but given enough time and care I was able to have it produce some of the octagonal sections needed to make the guard and pommel, in fact it had to make quite a lot as it turned out the assembly of these sections was quite challenging and I messed up several attempts before getting it right. The timber was cut to approximate size and them clamped up with the octagonal steel sections and drilled through so that everything aligned perfectly.
I forgot how much I hated cold-riveting by hand back when I was trained, it's a horribly tedious process with many opportunities to go wrong! On the first attempt I made the mistake of attempting to put epoxy glue between the wood and metal to ensure a strong bond, it turned out this was unnecessary and wound up just making a huge mess and ruining a couple of bits of steel and wood. In fact it seems throughout this project, every time I deviated from the techniques that the original medieval smiths would have used, things started to go wrong. I guess maybe people who spent literally their entire lives learning how to do this and getting good enough to work for kings might have known what they were doing.... who'd have guessed.....
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After another couple of tries and another couple of failures I did get a guard and pommel riveted together correctly and neatly, and then finished them on the large linisher again to leave a flat surface next to where you grip and the rivet heads exposed on the outside as a decorative detail. The edges were finished and beveled also on the linisher and the flat backs then sanded down with emery paper up to 400 grit using a granite slab as a flat surface to ensure they didn't get too uneven. The teak was then oiled with 8 coats of danish oil and wax-polished. The holes in the center of each were then gradually opened out using needle files to fit the tang of the blade in a process that took about 4 hours.
With most of the parts now made it was time for a test assembly. The first stage of the process was "burn-in" the tang of the blade by heating it up to about 400C and then pushing the handle over it until the heat burns the opening wide enough for the tang to fit snugly. This had to be done before the final hardening of the blade as otherwise the heat from this process would ruin the temper of the blade and make it impossible to sharpen properly.
All the parts now made, it was time to harden the blade so it could take a proper edge, only problem was we didn't have a tank large enough to quench the blade in to harden it, so I got hold of some thick walled aluminium pipe and using some aluminium plate we had laying around and the [[Tools/mig|MIG welder]] I welded up a new, much larger tank, this one is big enough to do swords since I plan on trying to make a Roman Gladius at some point in the future. The tank is 700mm deep and holds about 20L of vegetable oil, we use vegetable oil for quenching blades instead of mineral oils despite the smell as they're considered a much lower health risk when heated to smoke point.
New tank fabricated it was back to the forge for the blade to be normalized and straightened (and re-normalized, and re-straightened, and re-normalized and..... you get the idea). Once the blade was stable and relieved of all internal stresses it was put through a process of grain refining which changes the structure of the metal to adjust the size of the crystal grains within it. Doing this maximizes the strength and toughness that can be achieved without lowering the final hardness too much. In the final forging process the blade was then heated to 900C, held at that temperature for a couple of minutes, and then plunged into the oil. After hardening the blade was cleaned up and the scale removed using the [[Tools/polishingwheel|buffing wheel]] before hardness testing. Testing it with the [[Tools/hardnesstester|ultrasonic hardness tester]] revealed a final surface hardness of around 53HRC which is a good hardness for this type of blade being hard enough to take a good edge but still tough enough to withstand hard use.
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