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Designing an effective dust collection system takes planning and a little know-how. In this article, we’ll introduce the most important considerations in designing a dust control strategy that really works.
For many hobbyists and owners of small professional shops, an adequate dust collection system falls in the “luxury item” category – with so many other tools to buy, it can languish at the bottom of the priority list for a long time. Here are a few reasons to start taking dust seriously right now.
Research continues into the health consequences of long-term exposure to workshop dust. In the debate over the seriousness of the health risks, one thing seems to be universally accepted: the risks are real. A quick search on the Internet will bring up hundreds of sources of information on the health consequences associated with wood dust exposure, including the federal Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Health and Safety (NIOSH), a part of the Centers for Disease Control and Prevention. Eye irritation, nasal dryness and/or congestion, prolonged colds, skin irritation, frequent headaches, asthma and cancer are among the specific conditions that have been linked to wood dust exposure. And the longer you’re exposed to wood dust, the more likely you are to become sensitized to it and have a reaction or experience other negative health effects.
In many small shops, “dust collection” means breaking out a broom and dust pan at the end of the day. Too many woodworkers routinely step over piles of shavings kicked out by a thickness planer or stand on a slippery, quarter-inch carpet of sawdust while they push the last couple of boards in a large stack through their table saw. It’s easy to put off clearing away a hazardous mess when you’re busy working. And that’s just what many woodworkers do, even though it only takes a second to slip on or stumble over a pile of debris and end up with an injury that will keep them out of the shop for a long time. Fire is another danger posed by dust buildup. If you’ve ever used kindling in a fireplace, you know that wood ignites very easily when it’s cut into small pieces. It takes surprisingly little – a stray spark from a grinder, for example – to ignite the shavings and sawdust that your power tools produce. In extreme cases, fine airborne wood dust can reach levels that cause it to spontaneously explode.
It’s hard to do your best work if you’re trudging through mountains of shavings and coughing in a cloud of dust. A dust collection system can take care of that for you. Once installed, it will do a lot of the shop cleanup for you – while you work, not afterward. Not only will you have an easier time finding and getting to things in your shop, you’ll spend more time woodworking and less time cleaning up dust.
dust particles, chips and shavings, and fine wood dust. By far, the largest volume of debris created in most wood shops falls into the category of large-particle dust, chips and shavings. The stuff that collects under your table saw and behind your router table is composed of chips, shavings and dust that’s too large and heavy to stay airborne for long. A dust collection system that connects via hose or ductwork to your individual tools is the best way of keeping your shop clear of this large volume of debris. To take care of the fine wood dust that remains airborne, air filtration systems are recommended. These draw in air from your shop, filter out the dust particles and recirculate the filtered air. (To learn more about air filtration systems, check out the related article, “Dealing with Fine Woodshop Dust.” The rest of this article will focus on dust collection because it’s your first line of defense against wood dust exposure.
A dust collection system works by capturing woodworking dust and debris in a stream of air and moving it through the system’s ductwork to a collection area. It’s powered by a dust collector that uses a large induction motor to drive a special type of fan called an impeller. Together, they generate the large volume of air flow required to move the substantial amounts of dust and debris produced by woodworking equipment.
To keep the chips, shavings and dust moving through the system’s ductwork, a dust collector has to keep the air stream in the system moving at a certain velocity, measured in feet per minute (fpm), and has to move a certain (fairly large) volume of air, measured in cubic feet per minute (cfm). The relationship between air volume and air velocity is a function of the size of the duct: A stream of air moving at a given speed through a 12″ diameter round duct is transporting a much greater volume of air than an air stream moving at the same velocity through a 3″ diameter duct. In choosing a dust collector and designing a dust collection system, it is important to remember that air volume and velocity are interrelated. As you might expect, it takes a more powerful dust collector to move a large volume of air at a speed sufficient for effective dust collection than it does to move a small volume of air. Your dust collection system must be capable of delivering the minimum required cfm to each machine to which it will be connected. In general, the range for effective chip, shaving and large particle dust control is between 300 cfm for a tool with a lower dust and debris output, such as a scroll saw, and 900 cfm for a tool that really puts out the shavings, like a 24′ thickness planer. Many manufacturers publish minimum cfm requirements for each of their power tools. But to give you a rough ideal of what you’ll need in terms of air flow volume, the chart below lists common cfm requirements for popular shop machinery.
|Machine CFM Requirements|
|Table Saw – 10″||350 – 450|
|Band Saw – 14″||350 – 400|
|Jointer – up to 8″ wide||350 – 450|
|Planer – 12″||500|
|Planer -15″ and larger||600 – 900|
|Disc Sander – 12″||300 – 350|
|Horizontal Belt Edge Sander||550 – 600|
|Horizontal Belt Edge Sander||550 – 600|
|Vertical Belt Sander – up to 6″ wide||400 – 450|
|Drum Thicknessing Sander – up to 12″ drum||400|
|Drum Thicknessing Sander – 12″ – 24″ drum||550|
|Scroll Saw||300 – 350|
There’s another variable to consider besides the dust collector’s power: friction. As air moves through a system, it rubs up against the surfaces of the ductwork, has to round corners and is forced through restrictions – all of which inhibit air flow and create power demands on the system. Static pressure (SP), measured in inches of water in a column, is the loss in speed and volume that results. Static pressure build-up in a dust collection system is influenced by a number of factors. An excessive number of turns in the air stream produced by elbows, Y’s, and T’s are primary culprits. Duct size also plays a major role. Static pressure losses in in straight runs of narrow diameter ductwork are far more severe than in comparable runs of a larger diameter duct. The important thing is to be aware of static pressure and to try to reduce friction when you plan your system. Use the largest diameter hoses or ducts you can, and try to keep the number of 90° turns to a minimum. (Two 45° elbows connected by a short run of straight pipe would produce less static pressure, for example.)
To choose the right dust collector for your shop, you’ll need to consider the air volume requirements of the tools in your shop and also the amount of static pressure your dust collector will have to overcome. A large, powerful dust collector will, of course, move more air with more friction-overcoming force than a small, portable unit, and therefore can be used to service machinery that produces greater volumes of debris and have greater cfm requirements. Also, because of their greater capacity for overcoming static pressure losses, more powerful dust collectors can be located farther from individual machines, making them more advantageous for central dust collection systems.
Shop vacuums: Most woodworkers have a dedicated vacuum in their shop for cleaning up dust and chips after the fact. But for some handheld power tools such as sanders, biscuit joiners and routers, a shop vac might be the optimal dust collection solution while the tool is in use, providing sufficient power an d greater maneuverability than larger dust collectors. Shop vacs draw relatively small volumes of air but produce high levels of vacuum suitable for drawing small amounts of debris through the confines of narrow hose, small dust ports and the interior spaces of smaller tools. A wide range of fittings is available to connect your shop vac to most power tools in your shop. Just be sure to check the size of your shop vac hose and the size of the ports on your tools. You might need to get a stepped adapter or other connector if the two don’t fit together. (Rockler carries a number of adapters and connectors.)
Portable dust collectors: A portable dust collector is a good option if your priorities are affordability and simplicity. As the name suggests, a portable dust collector is moved from machine to machine, keeping it close to the tool it’s servicing and limiting the static pressure losses caused by long runs of ductwork. Setup is minimal – the dust collector connects to the dust collection port on the tool with a short length of flexible hose and a hose clamp. Quick-connect fittings such as Rockler’s Dust Right® components make connecting and disconnecting from individual tools even easier. Portable dust collectors vary from compact, wall-mounted units to free-standing units on casters, with a corresponding range of power and capacity. For a smaller shop, Rockler’s Dust Right® Wall Mount Dust Collector might be the perfect choice. It offers 650 cfm in suction capacity and doesn’t take up floor space. With additional mounting brackets, it can be moved from location to location in your shop. If you have a number of large stationary power tools, though, you might want to consider stepping up to a dust collection unit rated in the 1,100-1,200 cfm range. Dust collectors in this class will produce ample air velocity and volume to handle chip removal for even the largest home shop tools. Central dust collection systems: In a central dust collection system, the collector stays in one place in the shop and is connected to the woodworking tools with a system of ductwork. A central system has a couple of advantages over a portable system. The central unit can be placed in an out-of-the-way location where it doesn’t take up the most valuable space in your shop. Also, a central system is permanently connected to your tools, meaning that you can move from tool to tool freely, without having to stop work to switch the connection. But runs of ductwork, elbows and Y’s required in a central system mean greater static pressure losses. A dust collector used for a central system has to be powerful enough to overcome these losses and have enough air volume and velocity left over to move material.\