In my first shop, which was my apartment bedroom, I had no dust collection except for vacuuming afterwards. This sucked. Literally. Imagine…cutting boards and then leaving the room, closing the door, and waiting for the dust to settle. It wasn’t a good way to encourage more shop time.
So let’s assume you want some sort of dust collection system…even if just eventually.
When you’re thinking about your dust collection design, you probably have some images in your head of what other shops have. But your shop is unique, and your optimal duct layout will be unique as well.
Before you even think about sizing your dust collector, ductwork diameters, etc., you have to kind of know the overall layout and configuration of the ductwork. Even if you have none today.
I’ll go through how I figured out my current set-up, and the “why”.
Dust Collector Location
The first thing I thought about was where I’d be putting this dust collector thing. Next I thought about where the air-hungry tools are, and let that be the starting point for the duct routing.
Above all, you want the dust collector to be “out of workflow” in your overall shop layout. I didn’t want to compromise my “work flow ergonomics” at all. I want to be able to go from tool to tool easily, have plenty of room to work, and keep my infeed/ outfeed areas clear of hoses and wires.
To many, this means putting the dust collector in a corner. That’s what I did; it’s in an almost untraveled portion of the shop. It’s completely out of the way but not too far away from the tools that need lots of CFM.
To keep any one duct run shorter, I opted to “split” the mains; have one main duct travel to the right, and the other to the left. Having one long main trunkline could mean more than 30 ft. of duct in a single tool’s run (main plus machine branch) which is going to have high losses.
Think “longest run”, from the dust collector to the furthest tool; this is usually what you use to calculate your system’s static pressure (resistance to airflow). The more you can reduce that the more air you’ll get which means smaller particles from further away from the suction-source won’t escape.
By putting the collector in a position that allows you to split the main ducts between CFM-needy machines you’ve begun to optimize your ductwork already. You could position the collector in the middle of your shop and spider the ductwork out radially to each tool. If you don’t mind the visual obstruction (dust collectors are tall), then this can work pretty well. For me I want the feeling of an open space. So I want a clear view all around the shop.
WoodChip Tip: Don’t be afraid to think of things not commonly seen, such as two smaller dust collectors on opposite sides of your shop. If you’re limited by voltage, say you can only do 120V dust collectors, then two 1.5 Hp machines would be a nice choice. Each subsystem would have a much shorter duct run, and therefore less static pressure (resistance to airflow), and more CFM to help get the finer dust (which is more dangerous to your health).
Click here for the woodworking plans: Dust Collection Plan
Location of Horizontal Main Ducts
Assuming you are designing a more permanent system with ductwork, you’ll probably want to have “main ducts” that originate from the collector. From there you’ll have branches that pick up the various tools and stations.
Now where should you locate these mains? There are several options, which will vary depending on your shop’s construction.
Horizontal Main Configuration Choices:
- Overhead and along the walls, which is what I went with to keep ductwork out of the way in case I want to maneuver long boards. I have branch ducts in the middle of the ceiling but the mains are primarily along two walls.
- Overhead either diagonal across the shop or in the middle of the ceiling, which will help keep the overall duct run from any one machine minimized, if you only have one main duct. Just be aware that you now have more stuff over your head that can get dented from carrying stock around the shop.
- Low along the walls, which some people prefer (I had this design in my Ladera Ranch one-car garage workshop) to run branches low and directly into machines along the wall. This works well in small shops that have the tools along walls. The “open space” for you to maneuver is toward the middle of your shop. This way the branch ducts aren’t a tripping hazard and you’ve minimized their length.
- Under the floor, which if you have the clearance such as a crawlspace or a built-up raised floor (or even a shop on the upper floor of a building!) can help get ductwork out of your way entirely. The only thing I can’t get past is the branch ducts have to pop up somewhere and go through the floor to each tool. This limits rolling the machines to reconfigure your shop, and also can get in your way walking around or a shop cart pathway. This can be minimized through careful placement and layout of your stations. See Vic Hubbard’s shop (of Tumblewood Creations); it looks great and he did all the right things with regard to duct fittings, etc. Very nice job for sure.
In my Ladera Ranch 1-car garage shop, I started out with no dust collection; an open door was it.
When I did finally buy the Jet DC-1100 (which I still have today, and works just great), I knew nothing about how to set up a system other than the engineering HVAC know-how I had. Since it was such a small shop with just a table saw, router table, drill press, a bunch of hand tools and hand-held power tools, I just had to hook up two stations to the collector.
Both stations were against the long wall to give me the most open maneuvering space possible. It just made sense to route the main duct low along the wall and flex hose directly to each machine’s port.
Now that I have tools located more in the middle of my 3-car garage shop (in clusters for workflow purposes), I have to think a bit differently about what duct routing makes sense. This requires a balance between the shortest runs possible to each tool and not having too much overhead ductwork getting in the way of carrying long boards around.
Location of Branch Ducts
Branch duct configuration is heavily influenced by the main duct location and configuration, so it’s wise to think of both branches and mains at the same time.
Even if you have your mains run low along your walls, you can still have a branch duct riser to the ceiling, then route overhead to drop a flex duct down to a tool. Keep in mind this may be adding additional elbows and duct length to the system. Just make sure the branch ducts, which have to intrude into the shop space where the tool dust port is, don’t become a tripping hazard.
The last thing I want in a carefully planned shop layout is a bunch of ducts to jump over all the time, and this includes the flex hose portion that connects to the tool.
As mentioned above, tools along the wall generally aren’t a problem, because the branch duct and flex hose is behind the tool and you never step back there. However, vertical duct drops along a wall can sometimes interfere with wall storage. So, maybe design it so that the ducts go between storage cabinets like it’s on purpose!
But for tools in the middle of the shop, I decided to go overhead with the branch ducts and drop down near the back of the tool. From there, I imagined the infeed/ outfeed path and made sure that the flex hose and electrical cord weren’t in the way of stock travel, which meant offsetting the duct drop to one side a bit.
Literally play-act the operations at each station and see where the “no go” zones are for flex hose. I didn’t do this with my table saw and now cross-cutting a 6 ft. board runs into the flex hose before it’s all the way through the blade. In my revised layout, I’m moving the branch duct entirely to be in the “upper right corner” (when looking down at the saw), where nothing has to travel.
I also tweaked the duct branch location to accommodate the power cord to run up the flex hose as well, so I minimized how many things are in my way vertically. That’s why I have so many overhead outlets.
Remember to leave enough slack to be able to roll the tool around a few feet when you need more infeed/ outfeed room, temporary rearrangement, or creation of more open space.
WoodChip Tip: Keep in mind that if you have a one-person shop, and only one tool at a time is operational, you can size the mains pretty much the same as the branch ducts. This is because it’s one air quantity (CFM) going the whole run from the tool back to the collector. So in that case there’s no reason to upsize the ductwork as you move toward the dust collector. Why? Because you aren’t adding any more air from other machines as you pass by other branch ducts. And, increasing duct diameters too large for the CFM you have for one tool will mean the velocity (air speed) will get too low and won’t carry the dust back home…this can cause clogs and a potential for a fire given the right dust to air ratio.
In commercial shops, they run multiple machines at a time so the collector is sized for ALL of the CFM requirements at once. As air goes along the main it adds to the air from other branches. This means the ducts have to increase in size as they head back to the collector, which handles ALL the air. Typically you won’t see blastgates in these shops (except sometimes to balance the airflows) because air is being drawn all the time and varying the duct sizes is calculated to regulate the airflow by static pressure.
Location of Blastgates
Once you’ve thought about the branch duct configuration for each tool, think next about where each blastgate should go, and where the flex duct should begin from the branch.
I made the mistake of putting the blastgate too high in some cases, which makes it a chore to open and close. As I’m updating ductwork, I’ll be lowering some of these enough to reach but still leave enough flex duct to move the tool around. At my drum sander, for example, I have to use a stick or dust brush to tap the gate closed or pull it open because I can’t reach it. Oops.
Blastgates behind machines are a pain, too; I did this in my 1-car garage shop and it cost me a lot of time. Keep it reachable; this will influence the branch duct routing and connection point to the main a bit.
Flexible dust hose is inherently bad for airflow, because of the ridges on the inside surface. Their static pressure loss (resistance to airflow) per ft. of duct is often several times that of smooth sheet metal or PVC ducts.
So the goal should be to minimize their length while leaving enough slack to move the tool during normal operation and not have it pop loose. Shops that use only flex hose and have long runs of it, especially at 4” diameter, are really closing off airflow, probably well below the ACGIH recommendations. Like eating mashed potatoes through a soda straw.
Sharp bends in flex duct are also really bad. Keep direction changes to gentle sweeps. Think a bit in 3D when positioning the duct drops/ blastgates, and be aware of the tool hood connection location.
Tool Dust Ports/ Hoods
Often dust ports come with the tool you bought, like the 4” port in the back of your table saw. This 4” connection doesn’t mean it’s the right size for your system, or that it should be the only point of dust collection for that tool. Think about the main goal here: Pick up dust as close to the source as possible.
This means right at the blade, bit, or sanding drum, either above it, below it, or both. Think about how this blade or bit throws the dust/ chips and in what direction. Think about how you can capture and contain it long enough to be drawn into the tool’s dust port.
On a table saw, for example, it’s wise to look at an overarm guard, where there is a shield over the blade to contain/ direct the debris and then suck it up through a flex hose. This means you’ll have two dust ports; one at the blade guard and one at the back of the cabinet.
The same goes for the router table and bandsaw; dust winds up both below the table and above the table. So it’s wise to collect both. The “hood” should be shaped so it deflects and directs the dust towards the flex hose connection. Some of these you can make yourself; others they sell at woodworker’s supply stores.
WoodChip Tip: The tool port size that came with your tool isn’t calculated from anything; it’s just typically either 4” or 2-1/2” because those sizes of flex hose are readily available and that’s what people want. But people don’t know what they NEED. Some tools need a certain amount of air (CFM, or cubic feet per minute). A 4” dust port can’t support the higher CFM without excessive static pressure losses. So to me it’s better to size your system and branches to each tool first and then match the right tool port/ hood to that. For example, my 8” jointer gets clogged with curly shavings all the time because the 4” port can’t handle it; I also don’t get enough airflow because the flex hose and branch duct are 4” when they probably should be 5”. My anemometer supports this, and my static pressure calculation spreadsheet does as well. Time for a new connection port.
Inlet Duct to the Dust Collector
A lot of woodworkers ignore the connection to the dust collector itself. There are two things to consider when your “main” duct connects to the impeller port.
The first one is when you change the dust bag or bin, you will inevitably move the collector around a bit. Mine’s on wheels to help make it easier to maneuver. So as a result I put a short flexible duct (6” diameter) between the sheet metal main duct riser on the wall and the sheet metal horizontal duct that comes out of the impeller. This is so I don’t break the sealed duct seams on the elbow by overstressing them when the collector moves around.
The second thing to know is that putting duct elbows directly connected to the impeller opening causes high pressure losses, called “system effect”. This is calculated using a formula. The system effect losses drop to near zero when you have a straight duct connected to the dust collector equal to 6 duct diameters in length. For example, if your main is 6”, then your goal is a 6” x 6, or 36” of straight duct out from the impeller before any elbows.
Optional But Helpful Stuff to Add
Some people like to add a floorsweep; I did, but I don’t use it much. If not designed properly, you can easily sweep metal screws and bolts in there and damage your impeller. More often you’ll sweep wood blocks/ dovetail pieces hidden amongst dust piles which can also cause damage. I added expanded metal screen to help mitigate this, and you could also add rare earth magnets along the edges of the floorsweep mouth, too.
On the duct riser from the floorsweep, I put a branch to a coiled 2-1/2” hose to serve as a shop vacuum. It works; I do get enough suction to pick up large dust piles and clean the floor. But again, you risk sucking up metal debris and large wood chunks. This can be mitigated by a screen at the inlet of the vacuum fitting you use.
Another thing you can add to your system is add some cleanout hatches (access doors) on your horizontal runs. Just make sure you buy good ones with a nice seal all around.
You can also add a “vertical cleanout” to duct risers; this is just an extra piece of duct at the bottom of where a horizontal duct joins the riser from below. So instead of an elbow as you go from low horizontal to vertical, use a wye fitting and cap the bottom. This lets debris that falls out of the vertical duct airstream to settle in low capped branch. Every so often, open this cap and clean out dust that couldn’t be drawn upwards to the collector (but remember this is a symptom of velocity being too low).
Make Your Plan
Alright, once the overall layout starts to take shape in your mind and on paper, you’re ready to start calculating airflows and sizing duct. This will also help you choose your dust collector if you are about to buy one.
You might discover that your static pressure is too high in your layout, so you can make decisions like upsize your ductwork (while checking that minimum velocities are maintained), getting better lower-loss fittings, reducing the duct distances, and/or upsizing the collector’s motor/ impeller capability. Or you can turn the whole thing upside down and use two collectors, creating two smaller systems.
Click here for the woodworking plans: Dust Collection Plan
For more guidance in assembling your Workshop Design, click on the Starting? Go Here! category and read those first.
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Gotta get more clamps,
I adopted Crayon from the local animal shelter, Animal Friends of the Valleys. The process was really easy, and you can get a preview online before you go. Once you get there, you can browse around; you can make multiple visits until you find the right match for you. It was surprisingly inexpensive, I got a history on her (shots, spay, backstory, paperwork, etc.). This is pretty much the only way I’ll get any future pets now.