I've posted an instructable about making a fixed blade knife. It'll be useful to read that first, because in this instructable, I will not go over those steps again, but merely focus upon the nuances involved with creating a folding knife. A link can be found here: http://www.instructables.com/id/Knife-Making/
This instructable is intended to be able to be read by those who are not familiar with knives, but I may use some unfamiliar terms by accident. If I do, please ask.
Disclaimer: I'm not responsible for any injuries(likely) or deaths(unlikely) that may occur as a result of your attempt to follow this instructable, nor am I responsible for what you do with the information you have obtained from this instructable, nor what you do with the knife you have made. Follow your local laws at all times!
Unfortunately, I get caught up with the work sometimes, and forget to take pictures. Thus, I will be using several different models to demonstrate the steps. All the parts are the same, and the instructions to build them are the same, but just be prepared for a sudden change in the knives shown.
This project is somewhat difficult, and requires familiarity with basic tools, as well as quite a bit of time. However, the price is decently cheap, and not counting the tools, only costs me around $25 per knife.
I'm going to try to get this instructable out first, since I can't find another instructable of this type, and then fill in with extra pictures. Any questions are welcome!
Step 1: What is a liner lock?
Feel free to skip this step if you know what a liner lock knife is. This step is just to familiarize those who do not know, and also give an overview of what we will be making.
The liner lock was invented by Michael Walker, who altered the electrician's knife to create this folding knife, with a ball bearing as its detent. The lock, when made correctly, is very strong, and also allows for wear.
The main parts of the lock are the stop pin, pivot, and the liner lock itself. When closed, a detent built into the lock holds the blade closed. A liner lock works because a spring in the side of the handle (usually titanium) is in the path of the blade and keeps the blade open until the spring is pushed over to the side. If one is right handed, when the knife is cutting edge up, the liner lock would be built into the left side, and will spring towards the right. Pictures will do the rest of this talking.
Terms to know:
Lock- what keeps the blade open (in this case, the titanium spring)
Stop Pin- What keeps the blade from traveling too far when opened and closed.
Pivot- What attaches the blade to the handle, and what allows the blade pivots on.
Backspacer- A chunk of material located near the end of the handle (opposite the blade). This is just a pillar of support the same width as the blade and the washers.
Scales- The handle materials. G10 is a really good material to start with- it's strong and easy to machine, although a mask must be worn to protect against the glass fiber it will release. Micarta is a less hazardous material.
Pins- What holds the knife together. In the picture below, these are the two silver ones located near the blade, and the two brass ones towards the end.