p_atrick wrote: ↑Thu May 25, 2023 10:42 am
Chad,
I reread this thread. What a great collection of pictures, kind words, and stories from you and Sal. What I liked most was your walking through of your thought process on features of the knives. I had no idea back locks were that challenging. Back on Page 4, you talked about changing the lock type of the Piute or creating a liner lock version of the Heron. Just curious about how this is turning out. What have you learned, what do you like, what do you dislike, etc.? To me, the decisions behind the product can be just as interesting as the product itself.
Hi Patrick,
Frankly, I just had to go back and re-read the thread to be able to remember what all had been written here. First, thank you for reading all of that! It was a lot! I appreciate your interest. Jeez, that xplorer guy is a windbag (or the whatever the typing equivalent is).
I get the impression that just about everyone has no idea how hard it is to design and build a back-lock by hand, particularly a mid back-lock. I think the fact that back-locks like the Buck 110 have been around longer than many knife users have been alive at this point makes it seem as though they must be easy to make. When I was first presented with the challenge to build a mid back-lock, I was aware of what every part in such knives (like the Native) looked like and I thought, "sure I can do that, it shouldn't be too difficult". I had been a knife maker for a couple years at that point and I had been a knife collector for decades already. Yet, the complexity of the engineering involved in those designs was still invisible to me. It turns out that the complexity of those seemingly simple parts and the precision with which they have to work together is far more than meets the eye.
I'll try to describe some of what makes this type of design difficult to make...
Within a roughly 190 degree semi-circle the arc of the lobe on the back of the blade has to provide for easy initial lock disengagement, an increase in friction as the blade swings closed for added safety, and an auto-close function that will safely hold the blade in the closed position. All of those functions have to transition smoothly from one to the next and must be balanced with an ability to open the knife easily in one hand. Spring pressure, leverage and the geometry related to the lock bar pivot location has to be fine tuned to get it all working properly. THEN, there has to be a means for the blade to stop securely in the closed position and not move the lock bar when pressure is applied to the spine while closed. The lock junction then has to be cut in a manner that allows it to open and close easily but holds tight with pressure applied to the blade (either upward or downward) without any lock movement. Lock geometry will not work correctly if the precision of the parts is off by .001" or geometry is off by 1/10 of a degree. The lock bar has to be able to provide the locking function in the open position and provide the auto-close pressure in the closed position while the spine must be in the same location in both positions. Then, I also wanted the lock cut-out in the blade to be covered by the handle while in the closed position and the blade tip to nest perfectly within the end of a handle that has it's own design requirements. That puts some additional limits on how far I can move the lock junction around to maximize the balance between auto-close and comfortable opening.
Everything I've mentioned (and there's quit a bit more) is closely tied together so that if you make an adjustment to any one thing it affects everything else.
Once a design is worked out, it's can be much easier to make using precision automated equipment like wire edm and certain cnc processes. But, making them by hand is always going to be a high-wire act.
If you simply take the need for auto-close out of the equation, a lock mechanism is infinitely easier to design and build (by hand).
I believe the reasons that I attempted to explain above are the reasons why I don't know of any other custom knife makers that design and build their own mid lock back-locks these days. I imagine there are others, I just don't know of any. I know of hundreds that make frame locks, liner locks and slip joints. I think what I see is most makers are smart enough to know they can get more money for a frame lock that takes less time to build. One day, I too hope to be a smart knife maker.
So, to address your questions re page 4..
Ultimately, I decided not to change the lock in the Piute. I made a couple more and built myself some tooling to make some of the steps more easily repeatable. I was able to make the process more consistently precise and much more manageable overall. Like anything, the more you do something and apply yourself, the better you get at it. For example, the latest prototype was built with Magnacut everything. But, for heat treating the blade I used a method to get to my desired HRC that didn't result in the sharpening performance and edge characteristics I was expecting. So, I made a new blade. For the second blade I used a different method to reach the same HRC and the blade performed as I wanted and expected. I was able to put that new blade directly into my existing prototype without changing or modifying the lock bar and the opening/closing/locking functionality still performs the same. In the past I could not have swapped a blade without also swapping the lock bar in order to make sure the lock functions correctly. The Piute (or whatever name is gets eventually) will continue to be a mid back-lock.
As for the liner-lock Heron design...that's become a separate project that I like very much as well. All project like that have a starting point, and then they evolve. I hope to put one of those in my pocket before the end of this year, but that's about all I can say about that one at this point.
Thank you again for your interest in this collaboration project!
Be well!
CK
:spyder: Spyderco fan and collector since 1991. :spyder:
Father of 2, nature explorer, custom knife maker.
@ckc_knifemaker on Instagram.
. BUT..it's a very clean simple 45! 
