How to make a Slipjoint Knife

Part 1 : Geometry - How it all fits together

The most difficult part of making a slipjoint is getting the geometries of the tang and spring to work in harmony. Many custom makers are designing their slipjoints so the backspring is flush with the back of the knife when it is opened, closed and at the half stop.  The illustration below shows how the dimensions of the tang works in conjunction with the backspring.

For illustration purposes, the dotted lines are for reference only.

The distances from lines A, B and C to the center of the pivot must all be the same in order to obtain a flush backspring in all 3 positions.

Dimension "A" should be approximately 10% longer than dimension "B"
This is to keep the blade from extending beyond the end of the backspring when the blade is rotated.