Dan,
Just so everyone knows what you and I discuss, here is a common way for us to install the encoder disc.
We manufacture a post. In this case it was designed to thread into the camshaft. There is a small aluminum "base" that has a countersunk hole.
The base is installed onto the stainless post, the encoder sits on top, and a "cap" is placed over the encoder disc (similar to an Oreo cookie).
Since the shaft is drilled and tapped for a screw, the entire assembly is sandwiched together once the timing is set.
This is for a retail customer, and is not adjustable by design, so there can be no mistakes made during installation. We could design an adjustable post for prototyping if needed.
The first picture shows the "underside" of the base where it fits snugly over the stainless steel post.