buttoning up a unisaw for dust collection question

[zapdafish]

I am trying to cover up all the holes on my unisaw to improve dust collection. While looking for holes and whatnot, I noticed that the top is not solid so that where it is attached to the cabinet, there is alot of space for air to come through. as in pic below. Whats the best way to seal up those big uneven gaps? I am using a magnetic vent cover to cover the opening needed to tilt the arbor.

Also, any idea if the base is open to the ground? There is a piece of metal that angles the dust as it falls to the dust collection port but I can see that it isnt a tight fit and if the base is open, I'll have to go in and weather strip that area as well.

 

[FredP]

silicone should seal the top to the cabinet but will hinder tuning it up later. my uni has a bottom in the cabinet. not sure if they all do.

 

[Woodman2k]

Steve,
try finding some soft foam or even the foam pipe insulation and cram it in there.I agree with fred that the silicone might come back to haunt you.I did my Uni with some strips of soft foam and it made a serious difference.I have not sealed all the other leaks but have made some hardboard strips with magnets to cover the slots for the blade tilt.
Greg

 

[McRabbet]

Before you get too carried away trying to stop up all of the gaps in your saw, remember that for every cubic foot of air that is pulled into the duct through the port connected to your saw, a cubic foot of make-up air must enter the space you are exhausting. As an example, stick some gum to seal around a straw in a lidded drink cup and try to suck through the straw -- you'll find you can't (and the cup with cave in)!

Ideally, you want air to enter the saw around the blade to carry sawdust down into the cabinet and to eliminate "bypass" air that just goes directly to the exhaust port without picking up any dust. If you use Zero Clearance Inserts (ZCI) for your saw blades and dado blades, much of the sawdust stays above the table, so an overhead pickup guard is the best solution. You can drill a finger hole to the left of the blade in the ZCI to help draw dust into the cabinet. Plugging some of the major openings (like those in your pictures) may help increase the flow at the blade, but the DC static pressure will increase due to more restricted flow. I would experiment with plugging some of the worst openings with what I've suggested in mind to see if you improve dust extraction. And not to discourage your efforts, you'll need nearly 800 cfm total airflow from your saw to capture dust from inside the cabinet and from above the blade (see Bill Pentz' website for more details).

 

[zapdafish]

ah, didnt think of removing so much air intake I might make things worse. I made some zci yesterday out of scrap and am seeing alot more dust being thrown onto the table. Guess it's time to look into getting a dust collection splitter to take dust from the top as well as from the base now.

 

[zapdafish]

now that I think about it, do I really need the DC collecting from the base going on as I run the tablesaw or just from the top? After it builds up some in the cab, I can attach the DC and suck most of it out. I never really felt any airflow going through the zci and with the new ones, the opening is set to the exact width of the blade so that it doesn't have a gap to drop down into the ts cabinet anymore.

 

[Makinsawdust]

now that I think about it, do I really need the DC collecting from the base going on as I run the tablesaw or just from the top? After it builds up some in the cab, I can attach the DC and suck most of it out. I never really felt any airflow going through the zci and with the new ones, the opening is set to the exact width of the blade so that it doesn't have a gap to drop down into the tablesaw cabinet anymore.

My answer to the above question I would say yes. The blade carries the dust into the cabinet. I have a lot more of the fine, bad for you to breath, dust exiting into the cabinet. What comes off the blade above does not seem to be as fine. Also, there will be times when you can't or don't want to use the overarm guard.

To your question about the bottom being closed in the cabinet. My older Rockwell Delta Unisaw is open my newer 2005 Unisaw is closed and funneled to the dust sport. So it depends on which model and how old it maybe.

 

[Howard Acheson]

As has been said, you don't want to seal up the saw. You need at least the same number of square inches of intake as you have for your exhaust. For example if you have a 6" exhaust port, you need at least 18-20 square inches of intake.

Also, don't try to do anything around the saw blade or ZCI. The board you are cutting will cover any holes you make negating any removal of dust.

Finally, dust collection is all about air flow and direction. The dust coming off the blade is moving at over 100 MPH. You will not be able to affect its direction until it slows down considerably. The best plan is to construct a deflector or chute to direct the airflow/dust flow into the exhaust port. Another option is to let the dust go into the bottom of the saw-box and then have a series of holes along the side next to the bottom plate and across from the exhaust port. That way the DC will cause air to be drawn across the floor of the saw-box and into the exhaust port.