Scimitars WIP

[JamesBrauer]

Spent last night working on these two pieces. I had a pretty nice scandi grind going on, but up around 120 grit, it turned bad. After some cussin' I figured out that my new graphite pad had worn down in spots, so my grinding angle was changing as I moved up and down on the platen. These are going to be finished off on the slack belt with more of a rounded bevel/covnex grind. I got up to 1200 grit last night. Tonight I'm going to get them wet polished, with the Klingspor micro-mesh belts I picked up when I was at their factory store in NC last month.

These are my third and fourth serious knives. The first two, I heat treated in my forge, then did a differential temper with the oxy-propane pilot burner on my bench burner. The big chopper I treated like this hacked through hardwood and would still slice paper, but I still think it was a little brittle. I scratch built an oven for annealing glass that uses an Arduino to control the ramps and soaks, so I'm going to try the heat treat in that oven this time to get a more controlled soak. I still need to experiment with a blade coating to prevent scale. I might do a dip in a mix of Pyrax/Kaolin, or I might use a ceramic paste designed for coating glass bead mandrels in the burner flame. I'll try to update how that works out.

For the scales, I got some Black Mesquite (is that the same as Texas Ebony?) that I am going to inlay with topaz and maybe a little silver scroll. It messes up my color scheme a little bit, but I'm going to use brass pins and mill then file brass blade guards.

Here is a horrible photo. These are about 14" overall.

 

[David Stifle]

Hang in there, James. Grinding a sharply curved blade is a bit tricky. Your next one's will be better, and the one's after that still better. It's a matter of gaining both knowledge and honing your motor skills. good luck!

 

[JamesBrauer]

I rough cut the scales for this project. Laid out with a marking gauge, cut on the bandsaw, flattened the edge of the wood slab on the jointer, repeated. With a stack of scales in hand, the bandsawn edges were run through the dual drum sander (80/120 grit) to remove the slight waves from the bandsaw.

The wood is Black Mesquite, wet with water to show the figure. I thought this stuff was from Texas, but it turns out it is native to South America and lacks the dimensional stability of Honey Mesquite. The plan was to use one of the most naturally stable woods I could get, to avoid using a stabilizer. Plan aborted. My vacuum chamber is welded, and just needs fittings and gaskets to get running. It will add some time to the project, but I'm going to stabilize these scales.

Thanks for checking this out.
James B

 

[Willie71]

I agree with David. I did a couple of larger recurves, and it was quite the experience getting the right motion to grind evenly. I am starting to develop some muscle memory, and it is getting easier. Secondly, I have a glass platen now, and what a difference it makes. Frank Niro sent it to me and it makes a huge difference. Thanks Frank!!!!

 

[JamesBrauer]

Thanks for the encouragement fellas. I really bit off more that I could chew trying to do such a long curve in a scandi grind. When these are finished, I'm going to go back to a flat grind on straighter blades, then work up to it. I've ground and sharpened wood chisels for years, and sort of snap the bevel against the glass backed abrasive, lock my wrists, and make successively longer strokes being careful not to rock the bevel. But all that went out the window when I built a belt grinder. On the belt grinder I can sort of feel that snap on a wide bevel, but when I had only had a 1/2" bevel, on a soft graphite platen (that wasn't flat), there just wasn't enough feedback to know where I was. These two blades are still cleaning up pretty nice, just not how I originally intended. I'll put up some pix with my good camera when I get these polished.

 

[JamesBrauer]

I had the camera out to photograph some blacksmith work to list on etsy, and staged a better WIP photo. The scimitars are ready to have the handles drilled then go in the oven for heat treat as soon as I finish writing code for my new USB thermocouple. Hammered out some quarter Mokume for a blade guard on the larger scimitar, pretty sure I overheated it and melted out any little bit of silver that was in there. Vacuum stabilized some Cocobolo and Black Mesquite for scales. Ground out an O1 clip point to convince myself I could create a Scandi grind.

 

[JamesBrauer]

I CNCd some blade guards. The brass piece has a wavy scallop milled in, then a mortise for the blade guard milled undersized and hand filed to fit the tang. The piece fixtured to the table is some mokume I forged, you can still see a big hammer whack. This one will get what I'll call a stack of wavy scallops on both sides.

Open source toolchain:

- Draft the toolpath in Cadstd, export as .DXF (win7)
- Use AceConverter to convert .DXF to gcode (win7)
- Manually add F05 and G61 to file head, M2 to tail (win7)
- Drive the machine with EMC under Linux (Ubuntu EMC distro)
- Machine is a Sherline mill with stepper drivers from LightObject