No mystery. Turbulence around the "zero" clearance keeps a lot up top. It
even works that way on bandsaws, as I discovered when I put on one of those
UHMW plates.

"Roy Smith" wrote in message
...

Interestingly enough, I get much better dust collection with the regular
throat plate than I do with a zero-clearance insert. I suspect it had
to do with the wider slot in the regular plate allowing greater airflow.