Recommendation? Folder lock geometry question

[Lucky Bob]

I don't currently have access to equipment to make a modern folder, so until I can get such equipment I'm putting my MechE degree to "good" use and designing out a knife. I'm working out the lock geometry for an internally-pinned framelock right now, and questioning the physics of the tutorials I've read/watched.

The Tactical Folding Knife by Terzuola seems to be the Bible for liner-/frame-lock design, and his statement on the stop pin, lock contact, and pivot ideally laying on the points of an equilateral triangle gets repeated, but seemed arbitrary to me. I did some basic force diagramming, and I don't see any reason why the shape of the triangle makes any difference.

Does anybody with experience making liner- or frame-lock knives have any reasoning, besides an appeal to Terzuola, for or against the idea of an equilateral ideal? Thanks!

 

[J. Doyle]

I've never even given it a thought......and likely won't. I want certain design elements in my folders and those things often dictate where the stop pin, pivot and lock contact end up.

Given that changing one single thing on a folder affects 8 other things, the lock contact/stop pin/pivot being an equilateral triangle is the LAST of my concerns. My locks are plenty strong with no issues.

I would bet that most modern folders AREN'T equilateral in that area.

 

[Geoff Flato]

I learned to make liner locks with a full length backbar rather than a stop pin. I worry about the blade sitting where I want in the open and closed positions, and the lock working. What shape of triangle the parts form never occurred to me, nor was ever mentioned by Frank in either our discussions or the time in his shop.