Does anyone know what this cutout is for?

[JoHnYKwSt]

The one of the left is the old style and I believe the one on the right is the new style. I think the middle is an inbetween but I am not certain.

 

[Paul Davidson]

I can't tell what the arrow is supposed to point at. What do you mean? Are you referring to the area near where the lock engages?

 

[JoHnYKwSt]

The cutout directly above where the lock engages.

 

[stjames]

Just checked a half dozen knives and saw nothing like that. Very curious, I can't think of a function it would serve...

 

[Ookpik]

The frame lock should only contact the blade’s locking surface for about .125 inch at the lowest part of the locking surface. If the frame lock contacts the entire length of the locking surface, the blade will rock up and down when it is locked open. The piece of metal removed by the cutout is not needed. The cutout makes the lockup of the blade easier to adjust.

 

[JoHnYKwSt]

Thanks for the reply. I had a feeling that was what it was for since my small sebbie, which I have opened and closed too many times to count has developed some play even though the lock is at 90 percent or so coverage.
When you say:

The frame lock should only contact the blade’s locking surface for about .125 inch at the lowest part of the locking surface.

Why .125? and what do you mean by lowest part of the locking surface?

 

[Ookpik]

The lowest part of the locking surface is the part that is closest to the bottom edge of your excellent picture. It is the part of the locking surface that is furthest from the blade pivot. The .125 inch is the ‘length’ of lock engagement, starting from the bottom edge of the locking surface and ending .125 inch up along the surface. The 90% coverage you mention is the ‘width’ of coverage, starting at the right edge of the locking surface and ending 90% across. The specification for a Sebenza is about 70% coverage.
The .125 inch comes from a book ‘The Tactical Folding Knife’, written by Bob Terzuola. That is the maximum length he recommends for the primary contact point of the liner lock. I’m guessing that a frame lock would be similar.
A picture would be worth 141 words.