So why a knife-edge suspension? What's the point - edge?
Well, I know it seems like overkill for a Wiener that runs on five ounces with less than a one inch swing with healthy overswing:
How much pendulum error can be produced in a one inch swing? Not much.
Not much but; Not much but the knife-edge suspension was designed to reduce CIRCULAR ERROR of the pendulum.
You can readily see how ribbon or thread suspended pendulums are prone to - can move in a plane other than a straight line. Because they can, pendulum can wander off a straight line course necessary for accurate timekeeping.
Machining of it is very critical because in order for proper performance, bed must always rest fully across the knife edge. Otherwise it can rock fore or aft on the knife.
Why articulated? SAME reason! If pendulum doesn't hang in the same plane as the knife - again it can rock fore or aft - not fully seated on the knife, defeating all the benefits of it.
Also very important that the knife edge be in the same plane as the pallet arbor as not so doing defeats some of the benefits provided by it.
In some old clocks, the bed and knife are inverted. That is, the bed is stationary and mounted to the backcock, while the knife edge is fixed to the pendulum.
Hope you liked my new akkazishun! (I do)