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.
