Why are some titanium frame locks sticky?

[Dknight16]

Is there a known reason for this? I have a few that do this including my latest Alias II. Is it surface to surface galling due to certain alloys? Or a rough micro finish after machining? Or perhaps something in the heat treating process? Or maybe the engagement angle?

Looking at some of mine, it's hard to see a visual difference. I mean, none of them look polished at the faces involved. Yet, they all feel different. Some don't stick at all, some feel a little rough, and others practically require multi finger strength.

I'd be interested in the facts if some of the technical people here know.

 

[saxon]

The primary reason is what is called, galling. ( rhymes with calling) Whenever two different materials with different properties of hardness rub together, the softer will slightly give way to the harder. Or, will be impinged more by the harder of the 2. That is why, when slip joint or lockback folders are made, the blade and lockbar will be made of the same steel and heat treated together so they won't gall with use. They are the exact same hardness. The other factor you mentioned is due to the geometry of the parts. Steeper contact surfaces ( a steep blade tang angle) will not cause the blade tang to grab as tightly onto the lockface of the softer titanium. A less steep relationship will allow the two faces to wedge against each other more tightly and feel more resistant when you try to unlock them. Strider was I think, the first, or one of the first, makers to use a radiused blade tang so it would give a more progressive lockup so that the natural galling wouldn't cause the lockup to lose it's geometry with time.