What is the base flinch chance for moves and items that add flinch chance?

Some moves, such as Waterfall and Zen Headbutt, have a flinch chance added into them if they hit. There is also an item, called King's Rock, that adds flinch chance to all attacks. What is the flinch chance on these moves and items, and what is the flinch chance when they are stacked?

Solution 1:

No, they don't stack.

From Bulbapedia:

King's Rock has a 10% chance of causing the target Pokémon to flinch when using a move that deals damage and does not already have a chance to flinch.

Also Razor Fang has the same effect.

Here's a list of moves that cause flinching, with the relative probability:

Source, Bulbapedia.

(It's worth noting that those moves may cause their targets to flinch only if the user of the moves hits first.)