# Derivation on torque required to raise load, isn't there a force disapearing?

I drew a little picture:

Try to use you imagination to view these pictures as profile of bolt threads. In derivation on torque required to raise load, the angle of friction (ro) is calculated like in the left picture. Then it says that due to the angle of the 'tooth', friction-angle is adjusted, like in the right picture. The problem is, a force F2 should exist, but they just ignore it. Why? I opend Karl-Heinz Deckers famous Maschinenelemente book, where it shows how to get the formula required to raise load, and also at one point it just ignores the F2 force (at least it acknowledges its existence in one of the earlier steps of the derivation, but then just ignores it). Can someone explain this?