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Dust Collection for the One-Man Shop
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Don’t throw away the broom just yet. Even the best dust-collection system won’t eliminate the need for occasional sweeping. A good system, however, will keep the broom and your lungs from wearing out prematurely. There are two main points to consider when choosing a dust collector. First, figure out the air-volume requirements of the machines in your shop (see the chart). Next, decide on what kind of hookups you are going to use: flexible hose, PVC pipe or metal duct. To see what size and type of collector would best suit a one-man shop, I gathered a sampling of machines, from 1-hp single- stage units to 2-hp two-stage collectors, including one cyclone: Delta (1½ hp single stage), Dust Boy (2 hp two stage), Jet (2 hp single stage), Oneida (1½ hp cyclone) and SECO UFO-90 (1 hp single stage). I used the collectors with my tools, which include a 10-in, cabinet saw; a 15-in, planer, an 8-in. jointer, and a 16-in. band saw. The horsepower rating is a fairly reliable guide to the performance of a dust collector (see the chart). Hookups, however, are everything. Too much flexible hose will rob even a big collector of power. PVC pipes, in short runs, work fine with a sufficiently powered collector, 1½ hp or more. Metal duct, not unexpectedly, performs best. Even an 8-year-old, 1-hp collector can collect chips from machines 25 ft. away when hooked up to a properly designed system. Using a 1-hp collector this way may seem misguided, like putting a racing exhaust system on a subcompact car, but the experiment illustrates how you don’t have to spend a fortune to get decent results. Every shop is different, of course, and your results may vary so use my findings as guidelines, not absolutes.
While trying out a number of dust collectors, I measured their performances under real working conditions, using flexible hose, PVC pipe or metal duct in my 420-sq-ft. shop (see the chart above). The resistance readings ranged from 3 in. to 5 in. I also measured collectors hooked up to a straight piece of 6-in-diameter metal duct, just to get a baseline, highest- possible performance figure. Collectors ranging in size from 1 hp to 2 hp have impellers (fans) sized from 10 in. to 1 2 in. in diameter. All things being equal (motor speed and impeller design), a bigger impeller coupled with a bigger motor will move more air than a smaller pairing. There are some differences among collectors; to learn more, ask a manufacturer for an impeller performance chart. As soon as any collector is hooked up in the shop, performance declines in relation to the length and type of hookup. That’s why smooth-walled metal duct, with wide-radius elbows and wyes, is better than PVC pipe. A 1-hp Single-stage Collector Can Handle Any Machine in My Shop The biggest sawdust producer in my shop is a 15-in, planer. And even a 1-hp single-stage dust collector can handle that machine, hooked up with about 6 ft. of 4-in-diameter flexible hose. I borrowed a new UFO-90, same as my old collector, to see if anything had been changed. It’s still the same machine, rated at 650 cu. ft. per minute (cfm) by the manufacturer, but when hooked up to 6 ft. of flexible hose, it moves about 420 cfm. That’s slightly less than the 500 cfm recommended for a 15-inch planer, but 90 percent of the time the 1-hp collector can handle it because I rarely plane 15-in.-wide stock.
One-hp single-stage collectors cost about $250. Some woodworkers buy two units and station them strategically in their shop. At 82 decibels (measured at 8 ft.), a 1-hp dust collector isn’t much noisier than a vacuum cleaner, and each one takes up about 3 sq. ft. of shop space. I also used the 1-hp collector with a PVC duct system (4-in.-diameter pipe and fittings) and measured the moving air volume at the table saw-jointer connection, which is at the end of about 25 ft. of pipe and hose. At that distance, because of increased resistance, the air volume drops to under 300 cfm, less than recommended for woodworking tools. In reality, however, one can live with that. But if I’m face-jointing wide boards, the collector can’t always handle the volume, and chips jam the jointer’s dust port. Maybe 80 percent of the time it works okay. When I hooked up the 1-hp collector to a newly installed metal duct system, with my tools in the same configuration as be fore, I was really surprised. The air volume was back up to 360 cfm, very acceptable. Then I hooked up my old 1-hp collector, which is outfitted with oversize felt bags (available from Oneida Air Systems) that improve airflow and capture fine dust (see the sidebar at right), and I measured almost 400 cfm. That’s a significant gain.
A 1 1/2 Collector Can Be Hooked Up to Longer Runs of Hose or Duct
As you might imagine, hooked up to one machine at a time, a 1½-hp collector does not have any trouble removing chips, even with a long (12-ft.) run of hose. Delta rates its 1½-hp collector at 1,200 cfm, a number that is derived in a lab, not under real shop conditions (for more on manufacturer specs, see the sidebar on p. 273). Hooked up to a 6-ft. run of 4-in.-diameter flexible hose, I measured about 500 cfm with the Delta and 470 cfm using an Oneida Air Systems 1½-hp cyclone collector. Cyclones and two—stage collectors have slightly more internal air resistance; hence the lower cfm reading. That’s about what you can expect from any 1½-hp collector hooked up to 4-in.-diameter hose. I also hooked up the 1½-hp collectors to two machines running simultaneously. Performance ranged from good to so-so, depending on how much sawdust was being spit out by my tools. The best way to direct maximum airflow to the tool being used is to attach a blast gate to each hose. Hooked up to a PVC duct system (a run of about 25 ft. of pipe), both the Delta and Oneida collectors captured most of the sawdust when running one tool. A 1½-hp Delta collector costs about $350*.A two-stage unit such as the Oneida costs almost twice as much. Penn State Industries also sells a cyclone collector. Both 1½-hp collectors performed exceptionally well when connected to metal duct and used with one tool at a time. With two blast gates open, the air volume dropped and was insufficient to operate two big machines at once. The larger-volume bags or canisters of 1½-hp collectors hold a lot of material, about 30 gal. worth, which means fewer trips to the compost pile, a big advantage over the 1-hp machines that hold about half of that. A 1½-hp single-stage collector takes up about 7 sq. ft. of shop space. But a vertically stacked two-stage cyclone such as the Oneida takes up only 3½ sq. ft. of shop space, a big plus in a small shop. More horsepower does mean more noise; both registered 85 decibels at 8 ft. The Delta comes wired for 11 5v but can be switched over to 230v. The Oneida comes without cable or switch. It can be wired to run on either current. A 2-hp Unit Can Sometimes Handle Two Machines at Once 2-HP COLLECTORS:
Hooked up to two 6-ft. runs of 4-in.- diameter hoses, a 2-hp single-stage collector draws over 350 cfm from each port, plenty for many woodworking machines. The 2-hp two-stage Dust Boy didn’t match the power of the 2-hp single-stage Jet machine, although it has other qualities that may be preferable (see the sidebar).When I connected the 2-hp units to the PVC duct system, they too were robbed of considerable power, but one machine could be operated at a time with satisfactory results. When connected to a metal duct sys tem, the Jet collector really moved a lot of air, 570 cfm at the table saw-jointer connection (after about 25 ft. of duct).With two blast gates open, the air volume was reduced to less than 300 cfm, still accept able for some operations. The Dust Boy produced slightly lower readings but still had more than enough power to run one tool at a time in any configuration. If you regularly operate more than one machine simultaneously, it would be wise to look at 3-hp or bigger dust collectors. The 2-hp machines are no noisier than the 1½-hp collectors. They cost more, how ever. The Jet is priced at $400; the Dust Boy sells for about $650. Most 2-hp collectors come wired for 230v. The Dust Boy can be run at either 115V or 230v.
Choosing Among the Options On the matter of choosing a dust collector, a two-stage cyclone gets my top vote. A small cyclone collector takes up less room, is easy to empty, and runs very clean. For example, on all of the single-stage units, even after running them for only 1 hour, fine dust appeared on the machine and in the area around it. That’s because it’s difficult to get a perfect seal between the bag and housing. The Oneida cyclone, outfitted with an internal filter, rubber gaskets and wide metal ring clamps, seals better. Two-stage units such as the Dust Boy (Delta also makes a two-stage collector) are also nice and compact. The Dust Boy takes up 6 sq. ft. and less vertical space than most collectors. The Dust Boy (as does the Oneida) comes with a Leeson motor and cast-aluminum housing and impeller (fan), and the sturdy plastic barrel holds a lot of debris, 55 gal. worth. Before it can be emptied, however, the heavy motor and housing must be lifted off. Removing the lower bag of a single-stage collector is an easy matter of loosening a band clamp. The real fun begins when you try to reattach it. If you’ve ever had to put your pants on with an arm in a cast, you’ll get the idea. The lower bag must be wrapped around the metal waist of the machine and held in place before the clamp can be cinched. Some manufacturers, such as Jet, add an elastic band inside the lower bag to facilitate reattachment somewhat. Woodworker’s Supply tried to solve the lower-bag problem with a clamp-on skirt accessory. The skirt and a standard 30-gal. trash can replace the lower bag. Because the skirt remains attached to the collector’s housing, it’s easy to cinch the lower belt that attaches the skirt to the trash can. I just wish the skirt were made of felt rather than the more porous woven fabric. This setup will reduce the air volume (the collector “breathes” through both bags) when using the stock upper bag. With a larger upper bag, I found that the cfm readings were not compromised. But if you happen to vacuum up any off cuts, they will make quite a racket rattling around in a metal trash can. Although many woodworkers, myself included, have used PVC drainpipe for duct without mishap, experts warn against using the material. The connectors (elbows and wyes) restrict airflow and the material builds up a static charge, which may cause a spark and set off an explosion. (Running grounded copper wire inside the pipe reduces the hazard.) Use PVC at your own risk. Metal duct and fittings are obviously better and will also last longer. I’ve broken half a dozen plastic blast gates in as many years. If you’re on a tight budget, go with flexible hose or build a metal duct system in stages, starting with only a couple of hookups. Your collector will work more efficiently, and so will you. Designing a Central Dust-collection System
Oneida Air Systems designed my ductwork, which is very typical for a one room shop under 500 sq ft The ductwork begins with a 6-in.-diameter pipe connected to the collector. At the first wye (split), the duct reduces to 5-in.-diameter branches. The 5-in.-diameter pipes serve the biggest tools (jointer, table saw and planer), even though they all have 4-in-diameter dust ports, which ensure good air volume to the machines. Also, you can change the dust port to a 5-in.- diameter connection for better performance A 5 in diameter to 4-in-diameter reducer is used to make the transition. The 4-in.-diameter branches that split off the 5-in-diameter line serve smaller toots, such as the band saw and router table Blast gates are installed at each tool. The final connections were made with flexible hose, which allows me to move my tools around. I used 24-gauge (mostly) snap-lock pipe, spot-welded fittings and aluminum blast gates which are available from many companies. (Avoid lighter-gauge metal duct designed for heating or cooling systems; it can collapse under vacuum.) A higher-quality system will employ 22-gauge spiral pipe and welded fittings, which are stiffer and more airtight, and yes, they cost more. Quick-Fit duct supplies from Nordfab are also premium priced, but the components go together easily and don’t require duct tape or caulk. Although individual 24-gauge components aren’t that expensive (a 5-ft. run of 5-in-diameter snap-lock pipe costs about $8), it all adds up. A very basic three-machine setup may be had for a few hundred dollars A system for half a dozen toots and a floor sweep may cost $500 or more. To help illustrate the photos in this chapter, an orange and black flex hose was used to make connections from pipe to tools; black flex hose, however, works fine. It’s best to use a minimum of hose because it produces about three times the friction of metal pipe. Friction will reduce the performance of the system All pipe seams and connections must be sealed with caulk or duct tape. Clear silicone caulk is a good choice because it’s virtually invisible and is easy to remove.
DESIGN HELP IS AVAILABLE Designing the ductwork for a central dust-collection system can involve a tot of calculations. For those of us who skipped math class, there’s help available. • Air Handling Systems of Woodbridge, Conn., has an on-line duct calculator program (www.airhand.com). The company outlines the concepts of duct design in a four-page brochure. • Oneida Air Systems of Syracuse, N.Y., will design a duct system free of charge for its customers (www.oneida-air.com). All that’s required is a shop drawing showing the types and locations of woodworking machines. • Nordfab of Thomasville, N.C., manufacturers of the Quick-Fit line of duct and fittings, offers a free design service. The company has a downloadable program, but you need a CAD program to run it. The company also offers a peel-and-stick shop layout kit for analog woodworkers. • If you wish to tackle duct design yourself, all of the necessary information can be found in Woodshop Dust Control by Sandor Nagyszalanczy (The Taunton Press, 1996). Sources:Air Handling Systems (800) 367-3828 Duct supplies and duct design American Fabric Filter (800) 367-3591 Custom-made dust bags Delta (800) 438-2486 Dust collectors Dust Boy (800) 232-3878 Dust collectors Highland Hardware (800) 241-6748 Dust collectors Jet (800) 274-6848 Dust collectors and supplies Kraemer Tools (800) 443-6443 Dust collectors and supplies ( Canada) Leneave Machinery (800) 442-2302 Dust collectors Nordfab (800) 532-0830 Quick-Fit duct supplies Oneida Air Systems (315) 476-5151 Dust collectors duct supplies and duct design Penn State Industries (800) 377-7297 Dust collectors and supplies Powermatic (800) 248-0144 Dust collectors Sunhill Machinery (800) 929-4321 Dust collectors and supplies Woodworker’s Supply (800) 645-9292 Dust collectors and supplies Wilke Machinery (800) 235-2100 Prev.: Controling Woodworking Noise |
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