For carvers primarily using hand tools, a simple broom and dustpan will make quick work of cleaning up wood chips. But, in most woodworking shops, large or small, the proliferation of machinery and power tools creates a lot of wood chips and dust. This debris represents two significant hazards; chips left to accumulate become a fire and tripping hazard. Shavings will combust much more easily than a solid block of wood and will help a fire spread with lightning speed, while finer dust makes walking on a smooth floor that much more slippery.
A dust collector is designed to be the first stage in your dust abatement program and must be able to do three things well: it must move a sufficient volume of air to capture the material generated at each machine; the air must travel at a sufficient velocity to transport even the largest chips and debris; and it must have filter media sufficient to capture and hold the finest (and most damaging) particles. Without the ability to capture and hold particles 1 micron in size and smaller, a dust collector becomes nothing more than a system to recirculate the dust and keep it airborne.
There are three types of dust collection systems suitable for home shops. Carvers, crafters, and those who don’t rely on stationary machines that produce large volumes of dust and debris can use a shop vacuum. This is very cost effective, doesn’t take up a lot of floor space, and is flexible – you can easily move the vacuum to the dust source. While vacuums move air at a high velocity, they don’t move a large volume of air. So while they do a good enough job collecting the fine dust and smaller wood chips from power tools (random orbital sanders, router tables, circular saws and the like) they are unsuitable for shop machinery. They also have a small storage capacity necessitating frequent emptying. Adding a cyclone lid (leevalley.com) and trashcan to this type of set up will greatly increase your chip storage capacity and reduce how frequently you’ll be emptying the vacuum canister.
The most common dust collection systems are the conventional single-stage ‘bag collectors’. They offer an efficient, cost effective way to manage shop dust. Increasingly you’ll see the filter bags on this style of collector being replaced by canister (cartridge) filters.
An alternative to bag collectors are the two-stage ‘cyclone collectors’ that use cyclonic action to separate heavy dust chips from finer dust. These systems are highly effective, but come at a premium price.
Conventional bag collectors come in a wide range of sizes from 1 to 2HP units designed for small home shops, 3 to 5HP units with larger air flow and bag capacity for larger professional workshops and mid-sized production shops, and larger two-stage collectors specifically designed for the big production shops. General Canada, for example, offers 16 different dust collector models.
There are four main components to a bag collector: the filtering medium, which is made up of a filtering bag or canister suspended above the drum; the impeller, which moves the air from the piping into the filtering medium; a motor that drives the impeller; and a containment medium, which is usually a plastic bag suspended below the drum. Rigid (metal or PVC piping) or flexible hosing connects the collector to the shop machinery.
You have the option of rolling your collector to the machine you need to use and connecting the two together with a short length of flexible hose or installing a permanent system of ducts to connect the collector to every machine in your shop. The decision will be based on the kind of work you do, the size of your shop, and the number of machines you have. These factors, in turn, will determine the size of collector you will need.
Typically, small 1HP collectors have an air flow capacity of about 400 to 650 CFM. You’ll get maximum performance from these collectors by connecting them directly to a machine as needed, and keeping the collector hose as short as possible, certainly no longer than six feet. For a system like this, you can use a 4″ to 5″ diameter collector hose.
For a larger home workshop, up to around 500 square feet, where you typically operate one machine at a time, a 1 ½ to 2HP bag (canister) dust collector will likely be a better choice. These collectors typically have an air flow capacity of from 1,000 to 1,600 CFM. You can have machines located further from the dust collector, and incorporate various connector fittings. For a system like this, you can use 6″ diameter hose. They will also be more suitable if you move to a larger shop in the future.
The ducting in our 400 square foot shop consists of 4″ flexible hoses connected to most machines. Some, like the jointer are stationary and are permanently connected to the system, but others, like the thickness planer are on a wheeled stand and are rolled out of the way after use. For machines that are portable, we have provided gated drops with flexible hoses that can be hooked up in seconds. All of these hoses and fittings impose a resistance on the air flow, but by keeping the runs as short and straight as possible with tight fitting connections, our 1 ½ HP Delta 50-850 provides enough suction to clear all of the debris we can throw at it.
|10″ Table Saw||350|
If you are connecting the dust collector to a set of ducts, design the ductwork for maximum efficiency before you decide which collector to buy. A dust collector hooked up directly to a machine will perform differently if that machine is installed at the end of a 16′ length of piping. Performance will also be affected by the size of piping you use and the style, number and location of fittings (such as elbows, Y-connectors, T-connectors, and blast gates). Several companies provide free duct design guides that can help you lay out your ducting (oneida-air.com, airhand.com, nordfab.com).
Each machine in your shop will require a certain volume of air to clear the debris it generates and you should ensure that the collector you purchase can accommodate the machine with the greatest CFM requirement (refer to the accompanying chart for the CFM requirements of some common shop machines). If you will be running two machines at the same time, then your system will need to handle the combined CFM requirements of both machines. In our shop we occasionally run the table saw and jointer or thickness planer at the same time, so we need a collector with a minimum CFM rating of 800 CFM (350 for the table saw and 450 for the planer or jointer).
The piping and fittings that convey debris to the collector impede the flow of air.
This is referred to as static pressure(SP) loss. You can easily calculate the SP loss for each machine. Calculate the number of feet of duct between the machine and collector. To this add 6′ for each 90º elbow along the line, 3′ for each 45º elbow and 7′ for each T-fitting. Then multiply the number of feet by .055 if you will be using 4″ ducting; .042 for 5″ ducting; or .035 for 6″ ducting. The result is the static pressure loss for the machine. In our shop the table saw is 18 feet from collector, and there is one 90º elbow, for a total footage of 24′ (18 + 6). We use 4″ piping, so the SP for our table saw is 1.32 (24 x .055). You need to do this for each machine in your shop. We occasionally run the jointer or thickness planer while the table saw is running. The SP for these two machines is .88 and 1.1.
For our system then, we need a collector with a minimum SP of 3.42 (1.32 SP for the table saw + 1.1 SP for the planer and 1 SP to account for air leakage and the caking on the filter bag).
Unless you are lucky enough to have an unlimited budget and space, installing the piping system for a dust collector will require you to make compromises as you go along. Invariably, the object is to reduce the impact the piping has on the efficiency of the system. Most collectors have dual 4″ intake ports. In some cases you may be able to remove the dual ports and use the larger opening for the main run of pipe. As the diameter of the pipe decreases, the volume of air you are moving will decrease but it will move faster. As the air speed in the pipes increases so does the friction, but this increase is exponential, not linear, so a doubling of the airspeed will cause a fourfold increase in friction. Eventually the added friction will eliminate any potential gains from an increase in airspeed. Use the largest diameter possible for your ducting to allow the impeller to move a sufficient volume of air to carry the chips easily.
CFM: Air volume measured in cubic feet per minute.
FPM: The velocity of air as it moves through a dust collection system, measured in feet per minute.
SP: The resistance to air at rest in a duct measured in inches of static pressure. Also called “friction”, “friction loss”, “resistance”, or “pressure loss”.
An excellent guide to calculating SP can be found in “Woodshop Dust Control” ISBN# 1561584991
Most 1 ½ and 2HP dust collectors are equipped with motors that allow them to be operated at 120 or 240 volts. Some of these collectors can have trouble starting when on a circuit with other machinery or if the circuit is at a distance from the panel. These motors take a few seconds to come up to full speed. As the motor comes to speed there will be a great in-rush of current to the motor and this can sometimes trip the circuit breaker. Switching the motor to operate on 220 volts will help eliminate this problem by reducing the voltage drop at the motor. Switching from 120 to 220 volts typically requires altering a couple of connections in the motor’s junction box or if in doubt; follow the manufacturer instructions, or hire an electrician to do it for you. Generally, it is best if a dust collector has it’s own dedicated circuit when used at 120 volts. All the collectors we looked at have 120/240 volt motors, except Craftex and Samona, which are only available in 240 volts.
The motor drives an impeller, which is what actually moves the air. On the models we looked at, impeller size was between 11″ and 12″ diameter. There are several designs in use by the various manufacturers as well as some different materials, but our preference is for a heavy welded steel impeller. These have the strength to survive unscathed after an encounter with a large chunk of wood or metal. Although highly unlikely, the impact of a piece of metal on a metal impeller could create a spark or cause a piece of hot metal to smoulder in the collection bag, so it is a good practice to empty the collection bag at the end of every shop session. Getting into this routine will reduce your risk of a fire and will leave the bag empty and ready for a new session in the shop.
The fine dust that accumulates on the inside of the bag is known as cake. As the cake builds up it restricts the particle size that will pass through the filter media, which is a good thing. After a certain point though, too much cake on the inside of the dust collector begins to hinder the airflow through the entire dust collection system. Periodically give the filter a shake to clear the excess cake.
Craftex CT095N – $369.00 busybeetools.com
Delta 50-760 – $419.00 deltaportercable.com
General 10-105 M1 – $399.00 general.ca
King KC-3105C – $319.00 kingcanada.com
Samona 80102 – $429.99 samona.com
SCTW 65200 – $369.00 steelcitytoolworks.com
For your dust collector to be effective, it should be equipped with a bag capable of filtering out fine dust particles. Fortunately most manufacturers now provide 1-micron bags as standard equipment. Bags rated at 1-micron are dense enough to capture the particles most dangerous to your health. The excess cake on the inside of the bag can be removed by simply banging the upper bag after you reinstall the empty lower bag. The bags provide between 12 and 20 square feet of filter area. There are woven and knitted polyester bags, and felted polyester bags. Felted bags offer the best particulate filtration. Most manufacturers provide these as standard equipment.
A number of companies also offer canister filters instead of bags. Canisters have a pleated filter media inside a rigid canister that provides a much larger filtering surface. This means the filter needs to be cleaned less often. Some of these filters are equipped with a flapper to help release the dust from the media. All the models we looked at come with an optional canister filter except the Steel City.
Dust collectors are loud, and you should always wear hearing protectors when they are on. While some manufacturers provide decibel levels, the figures aren’t overly useful; manufacturers will measure the dB level at varying distances from the collector. Current standards suggest that 85-86dB is the threshold at which hearing protection becomes necessary to avoid long term hearing damage and since the dust collector is only used when another machine is used, the dB levels will require you to use of some form of hearing protection.
If you only use your shop in the summer then placing the collector in a weatherproof outdoor enclosure is another option, though this might be problematic if you don’t live in the country and have neighbours that prefer more quite dust-free outdoor pursuits in the summer. Having the motor outside will also limit how late into the evening you can use the system before getting an angry visit from your neighbour. Because dust collectors move a great volume of air, placing the dust collector outdoors will very quickly remove all of the heated air from your shop in the winter. Placing the dust collector in a separate room in your shop can go a long way to deadening the noise but be sure that the room is large enough to remain cool with the dust collector running for extended periods. You can provide some baffled ventilation to aerate the room and contain the noise.
It’s always good to get the longest warranty that you can on shop machinery. While there isn’t much that can go wrong on a dust collector, you don’t want to be stuck having to foot the price of repairs. The best warranty is on the Steel City (5 years), followed by the Craftex and Delta (3 years). The remaining units offer one to two year warranties.
Considering what they provide (a clean shop and healthy lungs), dust collectors are a sound investment and provide excellent value for the money. With prices ranging from $319 (King) to $429 (Samona) you’re bound to find the right collector that fits your budget.
If you set up a dust collector in a permanent location in your shop and run piping to the machine, then having a remote control to turn your collector on and off can be a great advantage. Craftex (busybeetools.com), has both 110 and 220 volt models. The 110 volt model works with any collector up to 1 ½ HP while the 220 volt unit handles collectors up to 3HP. Both come with a control box, to which you connect the collector, and a battery operated remote control that operates the control box from up to 75 feet away.
• Use a 1-micron felt bag.
• Plan your ductwork to maximize the volume and velocity of air.
• Place machines requiring the highest CFM closest to the dust collector.
• Keep fittings, particularly T-connectors and elbows, to a minimum.
• Only open the blast gate for the machine you are using.
• Empty the collection bag outdoors at the end of every day to reduce a potential fire hazard.