||[Nov. 3rd, 2006|06:50 pm]
http://www.homeport.org/~ayen/photos/spoon/ , but instead I'm going to have to ask you all to just accept that I'd rather spend time in the workshop than fiddle with formatting. Sorry. If you have questions about the photo or the writeup below, please leave a comment.)(Note: this should have gone up months ago, and it should have inserted thumbnails linked to the photos at |
Spoon was a mace, a mace I've only seen in a photo. It was, according to my patron, stolen. I was commissioned to create a replacement.
The original Spoon was, from what I've been told, made from non-stainless steel, possibly not even hardened, with an irregular finish and not a whole lot of effort gone into fit and finish. Still, it had been loved by its owner and his friends, and the replacement was to be as close to the original in design as possible. I had only one photograph, mostly of the head of the mace, and some verbal descriptions to go on.
(insert photo here)
To figure out the overall sizing, I cut out just the image of the mace and enlarged it until it matched from guard to pointy bit the expected length of about 2.5'. Using the resulting images I created a line drawing of what I thought the mace should look like. After a couple of edits on the part of my patron, I at last had an image of what I was to make:
Since I had never made a mace before, I had to guess at the budget for construction. Since my patron was a cow-orker, I decided to only charge materials costs to avoid the appearance of irregularity, but I came up with a time-budget anyway.
(cut & paste time/materials budget)
The added costs for the different materials is due to the relative difficulty of working the various materials. If I had been working in high or low carbon non-stainless steel, I could have just fire-cut the flanges out, and welded them on with almost any method, including forge welding. If I had been working with non-hardenable stainless, I could have skipped some of the steps (spelled out below) for the welding process, and it would have been much easier to clean up and finish after welding. But, when presented with the options, my customer decided he really wanted the high-carbon stainless steel. Since it's one of the most easy to find and relatively easy to work with of the stainless steels, I decided to go with the old standby, 440C.
Since I was not sure if this would even work on the first try, I over-bought the steel for the shaft and flanges by a factor of 4. This is my usual method for purchasing stock, as this way if I need to start over, I've got the material already and don't have to wait days to weeks for more, and if I don't have to start over, well, I have enough to play with for a while. In this case, I got 20' of 2" x 1/4" for the flanges and 12' of 3/4" hexagonal stock for the haft.
(photos of stock)
Since the flange design was fairly simple, your basic scooped-sided triangle, I rough-cut the flanges with the cut-off saw, then ground to shape on the grinder. After receiving final approval on the flange design, I started the hard part: welding on the flanges.
Now, I knew that this was going to be hard. In fact, some fellow knifemakers on one of the trade lists told me it was "impossible" to do what I knew I was going to have to do, and even pointed me at a website that claims it is impossible to weld 440C:
"Q: How can an appendage be welded to an implement made of stainless steel 440C?
A: It cannot, because 440C is not weldable."
This is, by the way, a good way to inspire me. It also didn't hurt that in the technical documentation (when ordering steel, *always* ask for the technical info, steel can vary by manufacturer, and you don't always know where a particular batch came from) included instructions for welding.
It seemed pretty simple: pre-heat to 800-900F, weld making sure the temperature doesn't go below about 600F, and when you're done anneal the whole thing for 4 hours at 1300F. For maximum toughness, temper at 1,100F.
The first test piece welded up easily, using a TIG welder, pure argon, and the preheat. For filler rod I cut some strips of 440C from thinner stock I already had in the workshop. I took three drops from the flange creation, cleaned them up enough so I had bright metal, clamped them against a short piece of the shaft material with a c-clamp, then pre-heated with a hand-held propane burner, jammed on my welding helmet, and gently arc welded it all together. Four hours of annealing later, I ran the piece through a quick heat-treatment (440C is air-hardening, so heat treatment is easy: heat it up, let it cool down in still air, temper.)
On to testing! I was not really all that certain that the flange welds would hold up to normal use, so I wanted to make sure, before proceeding, that what I was doing wouldn't fall apart the first time someone actually used the mace on something. First, I clamped the shaft into a vice, leaving one flange exposed, then I took a 2lb hammer and started tapping on the flange to see what would break first: the weld, the flange, or the vice. Hey, it's an old vice. The flange held up fine until I started really whacking it hard, as in a 2-handed full-impact blow, at which point the flange cleanly broke in two, leaving a stub still welded to the shaft with a good 1/4" of flange or more. For the 2nd flange, I put the test piece in the vice vertically, with the flange to one side, the shaft held securely in the vice. Using a 2' monkey wrench to apply torque to the flange, the flange again broke before the weld failed. Not quite done yet, I tightened up the wrench again on the remaining flange, put a cheater bar on the wrench, and twisted again until it broke. This last time, it was the 3/4" shaft that broke before the welds failed. My methodology, it seemed, was sound, as were my welds.
(image of test piece)
I was ready now to begin construction of the final piece. I had my flanges cut and pre-polished, the same with the shaft, and I had riged up a jig to hold everything, two flanges at a time, in the proper positions. I clamped the first two flanges on, hit it with the torch until I was at the proper temperature, and fired up the TIG. Two more flanges. Two more and I'm done. hmm, isn't that shaft bending a bit? It shouldn't do that . . . . oh, shit. Yes, I'd managed to overheat the steel, which failed,dropping the nearly-complete head onto the floor, where it flew apart into pieces. You see, high carbon stainless is red short, which means that as you heat it, there are temperatures where it suddenly loses cohesion and falls apart, resembling nothing so much as white-hot cottage cheese. I had recently bought a new welding helmet, and had set it to too dark a filter, and so had not noticed the ever-rising temperature in the filtered glare of the arc.
I still had a couple of weeks, though, until the due-date for the mace, so it wasn't that hard to start over again. Another 8 hours making the flanges and shaft. Another couple of hours of prep work for the welding. Two flanges at a time, welding. At last, the welding was done, and into the heat-treat oven. whew.
After the post-welding annealing, and having noticed that even heavily tempered, the test piece was a bit brittle, I decided to go the extra step and do a sub-zero quench on the piece. After cleaning up the piece a bit, I painted it with a surface protectant to prevent oxidation, and carefully heated up the head and 12" of the shaft to the critical temperature, held it for a minute to make sure the entire piece was at temperature, then air cooled. While it was air cooling, I went out to my local welding supply and picked up 20 liters of liquid nitrogen. When I got back, the piece was hot to the touch, but not scorching, so I quickly finished cooling in the slack tub, then rigged up the cryogenic chamber.
My "cryogenic chamber" is a large cooler with a rack a few inches off the bottom. If you just stick a piece of hardened steel into liquid nitrogen, the stresses from such a rapid temperature change can cause the piece to break, or even explode. To prevent this, I put the piece(s) I'm working on on the shelf, pour in a liter or two of liquid nitrogen into the bottom, then close the lid for half an hour. Repeat until the piece(s) you're working on are at the same temperature as the liquid nitrogen (the piece, when submerged, does not boil if it is the same temperature as the liquid nitrogen). Once the frost had melted off the mace, I tempered in the heat-treat oven for 2 cycles at 1,100F.
(Insert photos of cold mace)
The final phases of finishing and furniture were all that were left to do. As the mace head did not lend itself well to the usual tool I use for polishing, the belt grinder, I broke out some flap disks and an angle grinder. Using these disks I was able to grind the welds even in the valleys between the flanges, and they're available in a number of grits, from 36 to 600. Once I had taken them as far as the flap disks would go, I use the buffer to bring the head and shaft to a final polish.
To make the guard and pommel, I took some of the 2" x 1/4" stock for the flanges and used a hole saw to cut out two disks as wide as I could make them in that stock. For the guard, I then drilled a 1/2" hole in the center, then using a piece of haft material as a template drew in the hexagonal hole, then hand-filed the hole to match the shaft. It wasn't perfect, but I was out of time to re-do it, so I hard-soldered it in place and cleaned it up as best I could. For the pommel, I just brazed it straight to the shaft. The grip I made out of deer hide, held on with epoxy.
All in all quite the experience. For future maces, it seems to take about 1 hour for each of the flanges, a couple hours welding prep, about 3 hours welding, about an hour heat treating (though several steps take hours, you don't have to be paying attention while something air cools), 4 hours cleanup, and another 4 hours of furniture and finish work.
If I were to do this over, I'd probably not use 440C, but instead go for one of the low-carbon stainless steels -- a mace is a bludgeon, and really doesn't need to be hardened, plus I could use the MIG welder with standard stainless filler wire for the welding, which would be significantly easier than the TIG in such close quarters. I'd also do some work on the balance -- this piece is very top heavy, which you might expect for a mace, but it's just too heavy for use as a weapon. To fix that, I'd either forge the shaft thinner between handle and head, or remove material, either way it should lighten the piece up by a few pounds. I may just do another using some of the leftover materials and do just that, possibly with some twisting in the shaft as well for some added texture.