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Dust Collection for the One-Man Shop Print  |  Back

From: Fine Woodworking

Page 1 of 1

Don’t throw away the broom just yet.

dustcol1.jpgEven 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 on p. 84). 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 singlestage units to 2-hp two-stage collectors, including one cyclone: Delta (11/2 hp single stage), Dust Boy (2 hp two stage), Jet (2 hp single stage), Oneida (11/2 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. bandsaw.

The horsepower rating is a fairly reliable guide to the performance of a dust collector (see the chart on p. 85). 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, 11/2 hp or more. Metal duct, not unexpectedly, performs best. Even an 8-year-old, 1-hp col-lector 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.

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 singlestage dust collector can handle that machine, hooked up with about 6 ft. of 4-in.-dia. 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-in. planer, but 90% of the time the 1-hp collector can handle it because I rarely plane 15-in.-wide stock. dustcol2.jpgOne-hp single-stage collectors cost about $200. 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.

Three styles of dust collectors The most economical and biggest-selling dust collectors are the two-bag, single-stage models. Single stage means the dust is sucked through the impeller (fan) and dumped into the lower bag. The upper bag collects fine sawdust and lets the exhaust air back into the shop.

Two-stage collectors are the next step up. The motor and impeller sit atop a barrel. Chips enter the barrel and are directed downward, although the swirling air inside may occasionally move smaller chips upward. A filter bag hangs off to one side and collects the finest dust.

Two-stage cyclones are at the top of the evolutionary chain. The motor and impeller sit atop a cone-shaped canister, the cyclone, which is connected to a trash can below. Chips or other large debris enter the cyclone and swirl downward, avoiding the impeller. The longer the cyclonic chamber, the greater its effectiveness at slowing down and separating large particles. Air is filtered either by a pleated internal cartridge or by one or more felt bags hanging off to the side of the machine. Internal-cartridge cyclones use the least amount of floor space. The upper bags or cartridge filters of all collectors must be shaken out occasionally to remove fine dust.

DANGERS OF SINGLE-STAGE COLLECTORS Debris entering a single-stage collector passes through the impeller, many of which are made of steel. Even a small bit of metal, such as a screw, can cause a spark when it hits a steel impeller. Dust-collector explosions are rare, but the potential is there. Debris, metal or otherwise, not only makes a racket when it hits an impeller but also imparts stress on the bearing and will shorten its life. I heard of a woodworker whose collector’s sheet-metal housing was punctured by a screw that entered the impeller.

One way to reduce the risk of fire is to choose a single-stage collector with a plastic or aluminum impeller. Although the impeller itself won’t cause a spark, metal debris striking the steel housing may have the same effect. Steel impellers are fine, however, if you avoid using the dust collector to sweep up miscellaneous debris off the floor or workbench.

I also used the 1-hp collector with a PVC duct system (4-in.-dia. pipe and fittings) and measured the moving air volume at the tablesaw-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% 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 before, 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 oversized felt bags (available from Oneida Air Systems) that improve airflow and capture fine dust), and I measured almost 400 cfm. That’s a significant gain.

dustcol3.jpgA 11/2-hp 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 11/2-hp collector does not have any trouble removing chips, even with a long (12-ft.) run of hose. Delta rates its 11/2-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 story on the facing page). Hooked up to a 6-ft. run of 4-in.-dia. flexible hose, I measured about 500 cfm with the Delta and 470 cfm using an Oneida Air Systems 11/2-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 11/2-hp collector hooked up to 4-in.-dia. hose.

I also hooked up the 11/2-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 11/2-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 11/2-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 11/2-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 11/2-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 31/2 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 115 volts but can be switched over to 230 volts. 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 Hooked up to two 6-ft. runs of 4-in.-dia. 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.

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 system, the Jet collector really moved a lot of air, 570 cfm at the tablesaw-jointer connection (after about 25 ft. of duct). With two blast gates open, the air volume was reduced to less than 300 cfm, still acceptable 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 11/2-hp collectors. They cost more, however. The Jet is priced at $400; the Dust Boy sells for about $650. Most 2-hp collectors come wired for 230 volts. The Dust Boy can be run at either 115 volts or 230 volts.dustcol4.gif





















dustcol5.jpgChoosing 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 an 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.

MAKING SENSE OF MANUFACTURER SPECS There’s a fair amount of misleading marketing specs on dust collectors. When an ad says a collector is rated at 1,200 cfm, what does it mean? Not much, really. Cfm stands for cubic feet per minute, a measure of the volume of air moving past a point of reference. The cfm figure needs to be put in the context of the amount of resistance, or friction, present (called static pressure, or SP). Air moving through duct or hose encounters resistance, just as a person would slipping down a water slide. The more bends and bumps, the slower the ride or the lower the air velocity and volume. Many manufacturers rate their machines without bags or duct attached.

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 The resistance readings ranged from 3 in. to 5 in. I also measured collectors hooked up to a straight piece of 6-in.-dia. 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. dia. to 12 in. dia. 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. Materials that affect airflow. The metal elbow (top), which is designed for central dust-collection systems, has a gentle sweep, which lowers resistance to airflow. Plastic PVC pipe has a tighter-radius bend and restricts airflow more. Ribbed flexible pipe also disturbs airflow, up to three times as much as metal.

dustcol6.jpgA 2-hp unit can sometimes handle two machines at once

Hooked up to two 6-ft. runs of 4-in.-dia. 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. 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 system, the Jet collector really moved a lot of air, 570 cfm at the tablesaw-jointer connection (after about 25 ft. of duct). With two blast gates open, the air volume was reduced to less than 300 cfm, still acceptable 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 11/2-hp collectors. They cost more, however. The Jet is priced at $400; the Dust Boy sells for about $650. Most 2-hp collectors come wired for 230 volts. The Dust Boy can be run at either 115 volts or 230 volts.

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 an 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.

dustcol7.jpgRemoving 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 offcuts, they will make quite a racket rattling around in a metal trash can.

dustcol8.gifAlthough 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.


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