Worked out the shelf / chute harmony thing. Left me with a shelf opening only 4" tall but that's enough for the SuperNova2 chuck - with the long spigot jaws. The shelf is 1/2" ply. the top in a 1/2"rabbet/rebate in the1 1/2" x 2 beech shelf front. The beech is pocket screwed from below into the insides of the bench sides and acts as a stretcher. The ply sits on 1/2" cleats screwed into the inside of the bench sides. The rear of the 1/2" ply shelf is supported only on the ends. The shelf span is about 35:inches and the rear of the shelf does flex just a little - if you push hard enough. Shouldn't be a problem in actual use.
Note in the picture below that the shelf sits back about an inch and a half from the front edge of the bench top. While that cut the shelf's depth down to about 10", the set back should keep debris from falling onto the shelf and the stuff on it.
And speaking of keeping debris off the shelf - because of my "sweep crap of the back of the bench top - feature" - the shelf needs a back to keep that crap from falling onto it, and the tools etc. on it. Oh, and that bench top easy cleaning "feature" means that in addition to debris going off the back of the bench top and down on to the debris chute, then to the front of the bench - TOOLS etc. can also jump off the back of the bench top, fall onto the debris chute and slide - ON TO / INTO MY FOOT! Explaining that to the folks in the ER would be emarassing.
So I need
- a lip at the back of the bench top
- no lip on the back of the bench top when I want to sweep it off
- something to close off the back of the shelf to keep debris off it
- a way to open up the back of the shelf to blow debris out the back
Hmmm - appears to be some conflicting requirements.
Here's my solution.