Vac Experiment 2

[edswoods1]

Another question I have regarding shop suction - I have a nice 220 v. dust collector, and am trying to build different hookups for the various tools. One is a 12" sliding compound miter box,for which I need some kind of "hood." What I see making is a big box to sit behind the tool with a cavernous arched opening to accomodate its swing and the hose at

the bottom. That's the best I can come up with. The tablesaw didn't come with a hose attachment on the blade housing, so I just stuck a sheet of plywood in the bottom of the enclosure with a hose-hole, and it works really well. My shop is connected to a storage facility with million-dollar vintage cars belonging to the landlord in it, so I have to watch my ps&qs with the dust, especially since it's one forced air heating system for the whole building.

[Jim Behning]

[Andy Dingley]

You rarely need "some sort of hood" for sawing. The chips are reasonably large, so they don't "float" like sanding or even routing dust.

Try making a _shallow_ hood instead, with a horizontal slot. You might even build this into the fence, by boxing the back and routing slots near the bottom of the fence. If you make these slots deep (along the airflow axis) and with rounded edges into the airbox then you improve laminar flow and improve "dust grabbing" range.

The idea is that the efficiency of dust and chip collection depends on the air velocity passing into the duct. For a fixed mass flow (i.e. input power) then this can be improved by using a small cross section to keep the velocity high.

If you make a large hood, then it probably intersects every dust particle going, but catches very few of them. Increasing the power either puts the pipe velocity up (noisy) or sucks your toupee off.

[edswoods1]

I do not see a question. Do you have one?

- Jim Behning

Sorry to be vague, the intent of my post was to present my idea for pros and cons.

[Robatoy]

I would start off by caulking and taping every crook and nanny through which dust could escape. Then I'd put a stack of filters in front of the cold air return. (Get them self-charging electrostatic ones from one of the Borgs.) Then continue with your other plans.