Tool Review: Home-shop Dust Collectors
There's more to dust collection than just sucking up debris. We'll show you what to look for in a dust collector costing less than $400.
Would you buy a dishwasher that didn't actually clean your plates and pots? How about a lawn mower that cuts only half the blades of grass it passes over? Of course not. You expect machines to perform their tasks. We're with you. And that's why we say you should not spend your hard-earned money -- and risk your health -- on a dust collector that fails to trap fine dust -- even dust too fine to see. In our test of 15 portable dust collectors, we found that all could move debris from the machine to the collection bags with varying success. However, nine of those units featured dust-capturing filtration so inferior, they merely recirculated much of the fine dust back into the air. And it's that breathable dust that medical studies have proved to be the most harmful to your health.
Before we get into filtration, it's important to understand how a dust collector works. The type we tested suck chips and dust into an impeller, which then spews them into bags strapped above and below a steel rim. The bottom bag collects what settles, while the top bag (and unfilled areas of cloth bottom bags) filters and traps the dust as air escapes through it.
A dust collector needs to move dust and chips at least 3,500 feet per minute to keep them suspended in the air and prevent them from settling in the duct. Multiplying the air speed by the area of the duct gives you cubic feet per minute (CFM), the performance spec cited most often in dust-collection discussions. Typical home woodworking machines have 4" dust ports and require a minimum airflow of 400 CFM.
But CFM is only one of two key factors in gauging dust-collector performance. The other is resistance, measured in inches of static-pressure loss. The very ductwork you need to channel the debris to the collector actually chokes that airflow, especially as you add length or change directions. For example, every elbow, wye, or reducer in your line creates resistance versus a similar setup with a straight duct of one size. The length of duct and material it's made of also adds resistance. (Ribbed flex-hose, for example, adds three times the resistance of smooth-walled metal duct, so it's important that you use as little of it as possible.) To determine the amount of SP loss you should expect to encounter, go to the site below, or read WOOD magazine 119 (December 1999), pages 16-18.
Figure Your Dust Collection Needs
Wood debris ranges from heavy particles (like planer chips) that quickly fall to the floor, to microscopic dust particles that remain suspended in the air for 30 minutes or longer and can't be seen without magnification. The smallest size a human eye can see is about 10 microns. (Human hair, by comparison, measures about 40 - 60 microns in diameter.) These dangerous, breathable, ultrafine particles easily escape through the porous woven-cloth bags rated at 30-micron filtering efficiency. You should insist on at least a 5-micron filter media (bag or pleated cartridge), but a 1-micron filter proves even better. These finer filtration bags have more pinholes per square foot -- to allow air to pass through -- than 30-micron woven cloth bags. So not only do these bags trap fine dust, but they also increase the collector's airflow by reducing resistance.
Some collectors come with a 1-micron top & bottom bag; a few others come with top bags ranging from 2.5-micron to 5-micron top bags with nonporous plastic bottom bags. The remaining models come with less-efficient bags top and bottom. You can upgrade to better bags or pleated cartridge filters from most of these manufacturers, or you can buy much larger high-efficiency aftermarket bags that provide more surface area to filter dust and allow air to escape.
Top Tools: Delta 50-760 and Grizzly G1029Z
Learn the complete results of our testing of the Central Machinery 45378-1VGA, Craftsman 21337, Delta 50-760 and 50-850, General International 10-105M1, Grizzly G1028Z and G1029Z, JDS 14040, Jet DC-1100A, Penn State DC2000B and DC2V2, Rikon 60-200, Shop Fox W1666 and W1685, and Steel City 65200 in the March 2008 issue of WOOD magazine, or download the review.
Comments ( 0 )
Add your comment
