A small insert doesn't collect dust as well as a large insert because
the small opening restricts the cfm. But a large insert doesn't
support the work as well.
Is this correct?
I was thinking that the insert behind the bit doesn't support anything,
so opening up the insert there would increase the cfm and improve dust
collection; make the opening an oval rather than a circle.
Does this make sense?
Assuming you are with me so far, would it be reasonable to make this
oval by screwing the aluminum insert to a block of wood, and going at
it with a hole saw? The material left could be cleaned up with file.
Or possibly a router? If I don't mind maybe dulling the bit, is a
carbide router bit safe on aluminum? I know I once erred with my
omnijig, and the router cut into the aluminum pretty effortlessly. I
just don't know how safe it might be, again holding the insert screwed
to a piece of wood.
If none of this makes sense, I broke a rib last week and the muscle
relaxant doesn't agree with me...