Dust Collection that Evolves with Your Shop
You know you need to upgrade your workshop dust-collection system when:
- Your workspace looks like a shop-vacuum showroom, with a different one attached to each machine.
- You postpone buying a jointer or planer because it would overwhelm your old vacuum or bury your shop in chips and dust.
- If the dust in your lungs doesn't choke you, the people sharing your dust-filled house will.
- All of the above.
Of course, a basic dust collector or cyclone plus ductwork can be installed for less than $1,000 while high-capacity systems cost several thousand—not exactly chump change. So, if you're about to make that kind of investment, install a system that will serve you for years to come, even as your dust-collection needs change (and they surely will). You'll find the extra money will be well spent if you value:
Healthier lungs. Few shop-vacuum filters and single-bag collectors trap 0.3- to 5-micron dust particles—the stuff that can lead to respiratory problems. (For the definition of "micron" and other dust-collection lingo, see the sidebar below.)
The option to add step-up tools, such as a 15" planer or 8" jointer, that need the power of a dust collector.
Less setup time and clutter. A ducted system eliminates tripping over extension cords and corrugated hoses, and repositioning a portable collector.
Convinced? Then start designing a system for both the shop you have today and the one you'll have tomorrow.
Learn the Language of Dust Collection
Before shopping for a dust-collection system, familiarize yourself with a few of the common terms you'll encounter during your search.
Static pressure resistance. Before a system can carry away debris, air already filling the duct needs to be moved out of the way. That produces static pressure resistance measured in inches. Unnecessarily narrow ducts, sharp duct bends, and corrugated hose increase static pressure resistance by restricting airflow or adding friction between ductwork and the air.
Cubic feet per minute (cfm). Be careful how a manufacturer measures air-volume movement. Measurements taken on a "free air" basis—without any attachments that add static pressure or hinder airflow—help you compare one collector with another. But they're not a real-world measure of how a unit will actually perform when hooked up to a system that creates static pressure resistance. Measurements figuring in static pressure resistance better mimic collector performance when hooked up to ductwork and tools.
Drop. A duct descending from an overhead main duct or branch to connect to a tool; drops typically include a 45° wye for the main duct, a 45° elbow, vertical pipe, blast gate, and corrugated hose to attach to the tool. Some use a wye splitter to serve two tools.
FPM/air velocity. This is the speed of air, in feet per minute, moving through the ducts while the system is on. Aim for air velocities of 4,000 fpm in the drops, and 3,500 fpm in the main ducts.
Micron. In this unit of measure for dust particles, 397 microns equals 1⁄64 ".
Plan a system for your changing workshop
First, estimate the dust-collection needs of your future, expanded shop. Make a list of your existing machinery, and what you plan to buy within five years. In a typical home shop, you'll likely be working alone on one machine at a time with the others closed off by blast gates. If you plan to share your shop, you'll need a collector large enough to serve machines working simultaneously.
Next decide how much your shop space might grow. Added space requires a more powerful collector to pull debris through longer ducts.
Then map your shop layout with the existing equipment as well as machinery you'll add. To lay out your shop, use graph paper and paper cutouts to represent the size and shape of stationary tools; a computer modeling program such as SketchUp; or an online tool such as Grizzly Industrial's shop planner, shown below.
Dust-collector suppliers will often help you position the collector in the shop and lay out the ductwork efficiently. The service is free for purchasers of larger cyclones.
We worked with Penn State Industries (800-377-7297) to lay out a 16×24' sample shop, below, that starts with a 10" tablesaw, a bandsaw, a 12" planer, a drill press, and a router table. Future tools include a 6" jointer, 10" mitersaw, 16" drum sander, and a belt/disc sander. Oneida Air Systems also offers a ductwork design service (800-732-4065).
This system designed by Penn State Industries uses a 2.5-hp cyclone and 6" ducts leading to 4" drops that connect to the tools using short, flexible hoses. (Existing tools are shown in green, future tools in blue.) Economy ductwork and connectors, instead of spiral ductwork and premium connectors, cut the estimated price from $2,403 to $2,044 (2006 pricing). Features include:
➊ The planer and (future) jointer both generate large amounts of dust and chips, so both are positioned as close as possible to the collector, where static pressure resistance is least.
➋ The drop to the tablesaw splits into two hoses—one for the saw's dust port, and another for an aftermarket dust-collecting blade guard.
➌ Diagonal runs cover a large portion of the shop for adding still more tools while minimizing the number of 90° connections.
➍ Even the drill press connects to the system by way of a rigid adjustable hose that can be repositioned at the drill-press table as needed.
Ductwork dos and don'ts
To avoid common duct-design flaws:
DO use the largest ductwork that fits your collector. Just because a tool comes with a 4" dust port doesn't mean you should use 4" main ducts or drops. Instead, look at the intake port sizes for the collectors you're considering. Most cyclones have intake ports of 6" to 8", and some two-bag collectors have 5"- or 6"-diameter intakes, so consider at least a 5" main duct. Tapered reducers, like the one below, change duct diameters with minimal static-pressure loss.
DO smooth out sharp curves. Think of air molecules as fast-moving cars on a freeway. Both change direction faster on a sweeping curve than a 90° turn. The PVC tee shown on the left below adds more airflow resistance than the metal dust-collection pipe's gradual bend.
DO eliminate bottlenecks near the collector. (See "Give dust a straight shot to the collector" above.) Instead of two 90° bends, use two 45° bends. Better still, raise the collector until the main duct leads straight into the inlet.
DON'T overuse flex hose. Corrugated tubing creates three times more static-pressure resistance than the same length of smooth pipe. Use just enough to link a tool to its drop pipe.
DON'T create long duct runs. A single duct of 30' or more that wraps around more than two walls of a shop reduces air velocity and increases the risk of dust buildup. Instead, hang one shorter main duct, with diagonal branches leading to the tool drops.
Buy enough suction power
To choose a dust collector that will handle your shop's future requirements, you first need to know which tool in your shop (or on your shopping list) needs the greatest airflow to pull away dust and chips. Because every foot of pipe and each fitting adds resistance to that airflow, you also need to know the amount of static-pressure loss between the collector and that tool. With your workshop layout and dust-collection system map in hand, use the charts at the end of this article to guide you from your floor plan to the collector you need. (Download this article here if you'd like to print a copy of the charts.)
Once you have both numbers, you're ready to shop. Skip references to "free air" or "maximum" cfm, and check manufacturers' literature and Web sites for performance curves like the example below.
Manufacturers' curves may show how the system performs under ideal, carefully controlled conditions with a new, clean filter. Time and real-world use may lower a unit's actual performance, so opt for the next collector size up from what you've calculated you'll need. That way, no matter how far woodworking takes you, it won't leave a trail of sawdust along the path.