Design considerations for dust collection
I am always glad to see and talk to so many woodworkers at wood shows and meet those who have read the articles in this magazine or have seen my postings on the wood forum.
One of the most common questions asked at the woodworking shows is: “I’m just finishing up building my shop and the first thing I want to purchase is a dust collector. What do you recommend?”
If you have just built your shop and don’t have all your equipment, you need to sit down and figure out what size of tools you have or will require. You can use cardboard cutouts of the tools (using the actual foot print size), placing them on the floor of the shop to aid in developing the layout. Locate the dust collector nearest the door that you will use to remove the waste from it. The last thing you want to do is haul your waste through the shop or down stairs. You should locate your thickness planer or thickness sander closest to your collector. The size of these two machines basically determines the size of dust collector you will need.
One woodworker informed me that he located his collector in the garage in a closet. (His shop is in the basement). He added that he had vented the closet back to the shop in the basement. While it is true that you must return the air immediately to the shop from the dust collector you must realize that this may create a potentially dangerous situation. For example, if you don’t bring the air back in, then you are putting the house under a negative and, therefore, air will come in wherever possible. The most likely source of air is down chimneys and vents. This can suck in harmful products of combustion. However, the above woodworker had vented the closet back to the basement, which would solve that particular problem. The next concern is to ensure that the closet is sealed, so that gasoline fumes and CO2 from an auto’s exhaust can’t migrate down to the basement (one isn’t healthy to breath and the other could relocate the shop, if it finds an ignition source). Be aware that if you choose this type of installation, you may be voiding your insurance policy.
Another woodworker informed me that he was finishing off his shop and had been thinking of running those unsightly pipes up through the (unheated) attic. I reminded him that we live in Canada and when warm moist wood shavings and air meet freezing metal pipes, the result is wood-cicles. He stated that he had that covered because he would run the piping between the rafters and under the insulation. This might alleviate the temperature change but you still need to be mindful of how high you’re trying to lift shavings. Such height would limit the layout of his system and necessitate the use of the more expensive long radius 90-degree elbows when dropping through the ceiling. After doing all this work, if he were to purchase other pieces of equipment, then he would have great difficulty in adapting the system.
It is best to stay around the 10-foot mark in height for piping. Develop a system that is user friendly when it comes to making changes and additions to your shop.
These “boots” are normally used for delivering air via the floor/ceiling registers in a forced air heating system. The boots come in a variety of sizes and can be easily adapted for our use.
The first one we’ll look at is the “angle boot”. (see lead photo)
Insert either a sheet metal or wooden baffle into the normal register opening to strengthen the boot and increase the velocity at this opening.
This particular boot is 2 1/4”W x 14”L with a 4” outlet. Insert at least a 1” baffle along what will be the upper edge of the opening. You can bend up a 1” baffle from sheet metal and pop-rivet it in place. (You can use a piece of wood 1” x 3/4” x 14”L).
The other thing that you will have to do is crimp the 4” diameter outlet so that you can insert it into your 4” straight pipe.
Next, connect to a blast gate (or shut-off gate) locating it about waist level for ease of operation. Installing a blast gate in the line gives a more positive seal than a flap on the sweep.
The second boot that I want to show you will require little or no modification. It is called an “end boot”.
This boot is 4”W x 12”L with a 5” outlet and it can be used for the radial arm saw. The small port in your radial arm saw’s blade cover will have to either be directed into this chute or blocked off. You will need to crimp the 5” diameter outlet on the boot and use a 5”-4” reducer so that you can hook up to your 4” piping. You will also need to place the saw in the parked position and then attach the hood to your table as close to the saw and the vertical column as possible.
Turn a couple of inexpensive heating and ventilating boots into productive dust collection hoods.