new unisaw(and others)ZCI and dust collection

[John Pohja]

After getting my unisaw this summer i immediately made up some zero clearance inserts. I've since noticed a lot of sawdust spitting up onto the table in a diagonal strip across the tabletop from the insert towards the left front corner of the tabletop and thought this was strange considering the advanced collection system on this saw. I could also detect more dust in the air around the saw. My Grizzly 1023 didn't seem to suffer from this problem.

I decided to see if the collection was better with the Unisaw's factory(nonZCI) insert installed. As it turns out there is virtually no dust anywhere with the more open factory insert.

Has anyone noticed reduced dust collection on their table saw when using a ZCI? I'm guessing that there is reduced airflow around the blade causing the problem, although as i've stated i never noticed the problem on my 1023. John

[glenn bradley]

Has anyone noticed reduced dust collection on their table saw when using a ZCI? Yes. Some wise person somewhere online recommended this (http://www.sawmillcreek.org/attachment.php?attachmentid=125494&d=1250441619) 1/4" wide gap at the rear 2" of the slot. It keeps the safety feature of the ZCI and the chip-out reduction but, allows better dust collection. Who knew? The exact "air return" requirements for your shrouded blade will probably be different.

[John Pohja]

Yes. Some wise person somewhere online recommended this (http://www.sawmillcreek.org/attachment.php?attachmentid=125494&d=1250441619) 1/4" wide gap at the rear 2" of the slot. It keeps the safety feature of the ZCI and the chip-out reduction but, allows better dust collection. Who knew? The exact "air return" requirements for your shrouded blade will probably be different.

Glenn, Never saw this feature before. What model saw do you have it on? John

[Charles Lent]

I'm assuming that you have a new Unisaw, because the older Unisaw cabinets have so many air leaks in their design that you are lucky if you can keep the sawdust from accumulating in the bottom with a dust collector is attached, much less keep it from coming up around the blade. You could drill a row of 1/4" holes in your ZCI to let air pass through it around the blade. A row along each side of the blade helps. It doesn't seem like this would work because the board that you are sawing covers them, but somehow they make a difference, although not that great IMO. If you have one of the older models you can go on a long search to find and plug all of the cabinet leaks. The slots front and back are the most difficult to deal with. I used pieces of magnetic rubber so they can move when you set up for a miter cut, but stay relatively in place to block air flow in any miter position. Don't forget the webbing in the underside of the cast iron top where it attaches to the base. I used pieces of pressed in styrofoam insulation here.

Charley

[Chris Rosenberger]

Below is a picture of the factory insert for the new design Unisaw.
The large slot starts 6 1/4" back from the front of the insert.

I have not noticed dust coming out of the cabinet when using either the standard or zero clearance insert.

The new design Unisaw requires a higher CFM dust collector then the old style cabinet saws, because of the dust collection shroud under the blade.
The dust shroud has a 4" hose going to it & there is also a dust collection opening in the bottom of the cabinet. If you only have a 4" line connected to the saw, then it will not pull the dust out fast enough.

If the dust collector does not remove the dust fast enough, the dust will be pulled back up from the shroud by the blade.

http://i123.photobucket.com/albums/o303/chrisrosenb/20101206_8.jpg

[John Pohja]

Below is a picture of the factory insert for the new design Unisaw.
The large slot starts 6 1/4" back from the front of the insert.

I have not noticed dust coming out of the cabinet when using either the standard or zero clearance insert.

The new design Unisaw requires a higher CFM dust collector then the old style cabinet saws, because of the dust collection shroud under the blade.
The dust shroud has a 4" hose going to it & there is also a dust collection opening in the bottom of the cabinet. If you only have a 4" line connected to the saw, then it will not pull the dust out fast enough.

If the dust collector does not remove the dust fast enough, the dust will be pulled back up from the shroud by the blade.

http://i123.photobucket.com/albums/o303/chrisrosenb/20101206_8.jpg

Chris, I'm hooked up to a Grizzly G0440 cyclone with a 5 inch pipe at the saw running into a 6
inch pipe,etc so i think i have plenty of flow. Maybe i need to duplicate the slot on the factory ZCI. Thanks for the photo. John

[Rick Potter]

I have wondered about this for quite a while. The part I don't understand is how it makes a difference in dust collection, whether you have a zero clearance insert or not. When cutting, the board being cut covers the insert anyway, and your kerf is the only air coming in, (except when you start and finish the cut naturally).



What am I missing? They don't call me the village idiot for nothing.

Rick Potter