# Cabinet Dust Collection Question



## Wondermutt (Jan 21, 2016)

Guys- I have a question about dust collection in cabinets. When you hook up a dust collection system to an older cabinet style wood working tool that was never designed for dust collection, do you want the collection basin/compartment air tight, somewhat air tight, or air vents in the compartment? I am making basins/compartments for some older saws and jointers and will make it to suit which way works best.

Thanks


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## pete724 (Mar 9, 2016)

In order for air(and dust and chips) to get OUT, then air has to get IN.


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## Wondermutt (Jan 21, 2016)

> In order for air(and dust and chips) to get OUT, then air has to get IN.
> 
> - pete724


Roger that. I was just curious if there was additional ports needed other than the ones that are created by the blade openings and such. If others are needed, how would a guy determine how much air or venting may be needed.


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## JBrow (Nov 18, 2015)

Wondermutt,

I am no engineer, but have been thinking about and struggling to improve dust collection on the shaper, router table, jointer, and table saw. I am also not sure how much my thoughts help, but for what they are worth:

From my perspective, a sealed cabinet is best. If a cabinet is completely sealed, it becomes far easier to manage and direct air flow. If building a cabinet, making it air tight during the build and then venting it is probably easier than trying to make a leaky cabinet air tight.

It would seem to me that if the only air entering the dust collector from the jointer is through its throat, then more chips and shavings will be captured, since air velocity is increased at the throat. However if the volume of air moved through the throat leaves the dust collector starved for air, problems of settling dust in the duct work could result. If the dust collector is starved for air, increasing the size of the dust port in the cabinet could fix the problem, which could increase air flow through the jointer's throat. If enlarging the dust port either cannot be done or fails to provide enough air flow, then adding a vent to allow some additional air into the cabinet could restore the duct collector to full capacity. With careful thought, the placement of the vent could improve collection within the cabinet, if the cabinet is of an open interior design. Since it may be difficult to determine the correct size of the vent, an adjustable vent, perhaps with a sliding door, could allow for adjustments.

Dust collection at the table saw or router table is a little different from the jointer. From what I have observed, a big difference is seen when two points of dust collection are employed at the router table. The first point of dust collection on the router table is at table side near the router bit. It captures a lot of shavings, but guards, fence settings, and table insert rings seem to restrict or disturb air flow allowing chips to accumulate in the cabinet. Adding a second dust port in the cabinet seems to capture those shavings driven into the cabinet by the router bit.

Determining port size for the dual dust ports can get pretty complicated. But from what I have gathered, ensuring adequate airflow in the main trunk line of dust collection system is required to keep dust from settling out of the air stream. Therefore, as an approximation, I have sought to ensure that the cross section area of the two dust ports added together equals or is slightly less than the cross sectional area of the main trunk line.

Depending how far you venture into this effort, a Pitot tube could come in handy. The Pitot tube is a simple device that allows one to compare air flow. For example, with the dust collector running and sucking as much air as it can through a wide open pipe in the system, an baseline reading can be taken. Running the dust collector while connected to the jointer setting on a sealed cabinet can give you a different, smaller reading. The smaller reading indicates the dust collector could pull more air if available, so perhaps venting or enlarging the dust port is required.

I constructed mine following Stumpy Nubbs' design. The end of ¼" diameter clear plastic tubing is inserted in the center of the air stream of the dust collector, just before the air enters the filters and is sealed for air leaks. The tubing is bent to the shape of a U and mounted to a board with marks every ¼" up the length of the board. The open end of the U tubing is up and filled with water colored with food coloring until about 4" of water set on each side of the tubing where it forms the U. When the dust collector is turned on, air rushing over the end of the Pitot tube pulls a vacuum in the tube, pulling the column of water up the tube toward the dust collector. The reading is the difference in the height of the column of water when the collector is off from when it is on or when sucking free air versus connected to a tool.


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## Firewood (Dec 4, 2013)

I added dust collection to my old Cman jointer and basically left an opening on the opposite end from where the dust port is mounted. It is about thr same size opening as the dust port so as to provide unrestricted make-up air. I think anything less will reduce your DC's potential CFM airflow.


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## kelvancra (May 4, 2010)

It's the happy medium thing, and, air out cannot be more than air in.

I have a cabinet saw with a four inch draw leading back to a three horse, four bag system. The only source of input air is where the top meets the cabinet, the throat plate and the tilt and raise wheels. I wouldn't seal them, but I did silicone any lower gaps I could find.


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## wapakfred (Jul 29, 2011)

> It s the happy medium thing, and, air out cannot be more than air in.
> 
> - Kelly


 Exactly. Instead of considering "sealing" the cabinets, give some thought to managing the air flow within the cabinets. Good DC requires lots of air flow. Sealing will only restrict it.


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## Wondermutt (Jan 21, 2016)

Thanks for the suggestions guys. I made a couple of attempts but it really hindered my DC's efficency.

I retrofitted a shrouded system that grizzly uses but it's discharge hose is only 2 1/2" and it was clogging up. Part of that was I sealed the cabinet and may have gone backwards.

Last question. Where can you get an airflow measurement tool? I plan on building the Stumpy Nubs manometer as well.

Thanks again.


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