I wanted to make an Everyday Carry Knife (EDC) that I could use for basically all or most of daily tasks. It had to be small, practical, useful for woodworking and crafts, useful as a box cutter and potentially for self defense. It had to be sharp enough to use as a box cutter and strong enough to hold abuse. And it had to be minimalistic.
I had a rough idea what I wanted the knife to look like, that's the first step, but the second step is doing research. You can kind of split this up in two parts:
- Look at random images of knives to see what's out there and come up with new ideas, no matter how weird that you wouldn't have considered otherwise.
- Read up on what makes a good knife with the features you're looking for, and then implement them into your design.
Based on that research, you make your final designs. I've seen waaaay too many knives to name them all, but some influences were Max Venom, Doug Marcaida, Bastelli knives, Kabar, Esee, Mora, Gerber, kiradashis, karambits and last, but CERTAINLY not least: Stanley knives. The first set of names are about knives that are based of martial arts, then a bunch of bushcraft knives. I wanted a blend of the features of those knives with a focus on woodworking, so I took the ring feature from a karambit, straightened the handle, and initially gave it a drop point knife.
Now that my design was set I just needed to build the thing :)
Step 1: Cutting Out the Shape.
For this step we need the following tools:
- Crayon to mark the outline (or make a computer design, print it out and glue it on the steel)
- Drill press or a drill with a steady hand
- Stepped drill bit or a HSS drill bit with a large enough diameter
- Stationary grinder or belt sander
This is actually the easiest step of all... and yet it isn't. Why not is covered in the next step: heat treating:
The easy part is taking a piece of scrap steel, drawing a picture of the knife I wanted to end up with and grinding out the shape. When I got to the heat treating I was worried I might mess up my pretty, shiny new knife, so I decided to quickly make another, less fancy one to test it on.
Step 2: Heat Treating.
So we had the easy part. We just made 2 knives that are ready for heat treating. One primary one and one quick test piece.
For the next step we need:
- Some way to properly heat the blade, high enough temperature and long enough of a duration (forge, stove, barbecue)
- Heat gun or hair dryer
- Container with cold water or oil
- Lots of sanding paper
- Sharpening wet-stones
The hard part is that it's actually not a good idea at all to use just any kind of scrap steel, because not all steel is equal, and it may not harden as well as you like in a later step. This is not something I was aware of when I started, and it gave me some trouble with heat treating later on. When I did my heat treating I used the rule of thumb that you heat up your workpiece until it stops being magnetic (around a deep orange color), then cool it down quickly in preferably oil, because if you used water you could get micro cracks and cavitation from vapor bubbles forming and imploding. Turned out, that was not enough to fully harden the blade.
Here are some links on the subject.
http://www.jayfisher.com/Heat_Treating_Cryogenic_P... If you take one point away from this link, try to understand the phase diagram and try and find out where in this diagram the steel you're using is located. And realize that this phase diagram is about steel/iron at gradual temperature changes. Not a sudden temperature drop like is done in hardening the blade.
A couple of other points (but really, go read the website):
- Carbon content of a knife steel should be over 0.8%
- Decalescence: The time used to heat the knife is important. Just using a magnet to test the steel doesn't mean the knife is ready to be hardened. A pyrometer can help, because it will tell you when the steel has finished shifting phase. When steel goes from one phase to another, it absorbs heat/energy, so the temperature doesn't rise if you keep heating the material. Once all the material has finished changing phase, the temperature will go up again. This is the same thing that happens when water turns to steam. It absorbs heat to make a phase shift from liquid to gas, and while this process is happening the temperature doesn't change. Once all the water had been turned into gas the temperature rises again and the steam absorbs more heat than was needed to change phase. That kind of steam is called over-saturated steam.
- Decarburization: If the steel knife blade is heated for too long or for too high of a temperature after the decalescence point, the carbon will start to migrate to the surface of the steel and bond with any free oxygen, decarburizing the steel. I think I made this mistake. I quenched my blade in oil and got a black crust, which is a carbon layer, but I'm not sure if it was from over heating or from the quenching oil.
Neither of my blades properly hardened. I don't know if this is because I used "mystery steel" and there was not enough carbon content, or if I just messed up the heat treating process. I treated the original test knife in a takeaway barbecue until it was no longer magnetic for a while (the aluminium of the barbecue melted), and the second blade I heated in my fireplace during winter. 2 different ways of heating, and neither of those blades hardened properly. Maybe I'll try again once I have a pyrometer and a proper little forge for knife making.
When both knives were finished I cleaned them up, sharpened them using wetstones and also gave them a nice patina protection by placing them in a container with vinegar.
Step 3: Making the PVC Holster
After doing the (failed) heat treating, I wanted to make some holsters. For this step we need:
- Breathing protection
- Paint heat gun
- pvc tubes
- Lots of clamps
- 2 straight boards
- Some soft cushioning to use with the boards (and clamps) as a press
- several pieces of scrap wood the thickness of your belt
REMEMBER TO DO THIS IN A VENTILATED AREA AND ALWAYS USE A BREATHING MASK WITH A PROPER FILTER! PVC fumes are toxic!!! So be careful not to get it to burn and give of fumes... either way, fumes or not, ventilated area or not, STILL!! use breathing protection with a filter.
The first holster I made was by heating a piece of PVC tube, placing the knife in the center while the PVC was still hot and squeezing it between 2 pieces of foam and 2 straight boards. This creates a shape that closely follows the curve of the knife. At first I thought this would give me the kind of holster that I wanted, but instead it turned out not so easy to work with this shape, so I used a different method.
2nd attempt: make a paper template, test this template with some scrap pvc, then make a real holster. I made a paper template, put the knife in it and made some adjustments to the design of the holster.
Then when I got to shaping the PVC into a holster, I hardly even used the foam and press. Instead I put the pvc flat on 1 board, put the knife on, fold the pvc over and press the top side with foam to make it follow the shape. Then I heated the pvc up a bit again and pulled the knife out to get a proper retention/fit. I had to do this several times to get it right.
I also wanted a belt loop so I used a lot of scrap wood that had the right thickness to form a nice loop and retention. This was done while wearing welding gloves so I could manually bend the HOT! pvc, and clamped down with a lot of small clamps. This also involved a lot of local heating and reheating. This step would not have been possible by simply throwing the thing in a press.
As a last step I cut up an old bicycle tube into a ranger band and closed the loop on the belt loop.
This was very much a learning experience. Hopefully the next knives and holsters will be better. If you enjoyed this instructable, please feel free to leave your comments, critiques and suggestions.