I invented the FFK and received a patent for it's locking mechanism last year. I am still developing it. I am on this forum to get qualified unfiltered feedback on it. I appreciate and respect your comments, even though they are a-bit colorful.
So why buy a fixed blade knife ?
This feedback is something you are going to hear from many users:
You are attempting something which is cool, but something that has been attempted before and hasn't had a whole lot of success.
People buy a fixed blade not just for strength, but also for tougher steels, larger handles, larger sizes, and lower costs. Some of the most appropriate grinds, the blade thickness, the steel itself, the heat treatment, and the size of a fixed blade may be utterly useless for a folder.
For example, a hard-use fixed blade will benefit from something like thick A2 steel, which is very tough, and heat-treated to a lower hardness. Both the steel and heat treatment favors toughness over edge retention. For harder outdoors tasks, this is often an ideal setup as you can beat the crap out of A2. A good 1095 fixed blade like an Ontario RAT5 can withstand damned near anything, and often at a price tag of under $70. No folder will ever come remotely near its capability, and the lock itself on a folder is only one component and not even the biggest issue.
But if you put that 1/4 inch thick blade of A2 steel on a folder, it's going to have very limited practicality. In general, folders tend to favor thinner blades using steels with edge retention over toughness, as they generally do not see the same type of usage, and intensity of usage as a fixed blade. Additionally, corrosion resistance may be more or less important here. On many of my folders, I like an angle approaching 15 degrees a side or less and blade grinds that favor slicing over durability. For a heavy use fixed blade, those attributes are arguably a terrible fit. There are many tough folders at the 4 inch size for under $200, such as the Benchmade 810 or Zero Tol 0560. But none of them can really fulfill the roles of a fixed blade.
If a folder which is attempting to fulfill both roles exceeds the combined price of a good quality fixed blade and a good quality folder, it's practicality for actual usage is somewhat limited. Additionally, the reality is that when a folder tries to fulfill both roles is that there is going to be serious tradeoffs in some areas, and this can further limit practicality and actual usage. Many knives with unusually strong locks wind up being more collectors items, concept designs, or conversation pieces than anything else. If an EDC weighs 10+ ounces, has a massive carry profile, and turns an apple into applesauce when you try to slice it, it's not going to be in a pocket for very long. If it is super effective slicer, super light, and compact, it's probably not going to be able to hold up to splitting some firewood or carving a hole into a branch. You noted you were using 440C steel IIRC. It's a great steel indeed, but I strongly prefer a tougher steel than 440C on my fixed blades, and am finding I really like steels with high wear resistance on my folders.
So what does this folder's characteristics favor? More folder or more fixed blade? And what are the implications (i.e., the tradeoffs) that will come with that in terms of actual usage compared to a standard folder or a standard fixed blade?
