What Makes Dust Collection Important?
Whether it's a large commercial operation, or a weekend woodworker's garage-sized shop, dust collection is an important consideration. At Rockler Woodworking and Hardware, we concentrate on supplying dust collection equipment and supplies designed specifically for the space, needs and budget of hobbyist and small professional shops.
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, and we'll offer some advice on picking out the dust collection equipment that's best for your shop. On this page, we'll begin by pointing out why woodworkers everywhere are beginning to take dust collection seriously.
- This Page: Dust Collection and Respiratory Health
- Safety Hazards of Letting Things Go
- A Better Woodworking Experience
- Controlling Two Kinds of "Dust"
For many hobbyists and owners of small professional shops, a adequate dust collector falls in the "luxury item" category - with so many other tools to buy, a dust collection system that really handles the dust can stay 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 involved in exposure to wood dust, 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 woodshop dust exposure, including widely recognized organizations like the Occupational Safety and Health Administration (OSHA) Here's an excerpt from its introduction to the topic of Wood Dust and Health:
Wood dust becomes a potential health problem when wood particles from processes such as sanding and cutting become airborne. Breathing these particles may cause allergic respiratory symptoms, mucosal and nonallergic respiratory symptoms, and cancer...
Safety Hazards of Letting Things Go
In many small shops, "dust collection" means breaking out a broom and dust pan at the end of the day. Too many woodworkers routinely climb 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.
As every woodworker knows, it doesn't take long to cover a shop floor with sawdust and shavings, and it's easy to put off clearing away a hazardous mess when you're busy working. And that's just what many woodworkers do, knowing that it only takes a second to slip 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.
Portable dust collectors are great for handling large dust particles, chips and shavings, and can provide your first line of defense against fine wood dust exposure.
The risk of fire is obvious. If you've ever used kindling to start a fire 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 papery shavings and sawdust that your power tools produce. In extreme cases, fine airborne wood dust can reach levels that cause it to be explosive.
A Better Woodworking Experience
Very few woodworkers do their best work while kicking through mountains of shavings and coughing out a cloud of dust. Once you have a dust collection system installed, it will do a lot of the shop clean-up 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 picking up dust.
Controlling Two Kinds of "Dust"
Air filtration systems rid the air in your shop of the harmful fine dust particles that your dust collection system misses.
The dust that a wood shop produces can be divided into two general categories: Large dust particles, chips and shavings, and fine wood dust. These two kinds of "dust" each have their own negative effects on your woodworking operation, and each requires a different strategy for adequate control.
On the next page: Keeping the chips, shavings and large dust particles under control.
Handling the Large Chips and Shavings
By far, the largest volume of debris created in most wood shops falls under the large-particle dust, chips and shavings category. Most of that mountain of "dust" that collects under your table saw and behind your router table in a short time is actually composed of chips, shavings and dust that's too large and heavy to stay airborne for long. A dust collection system is simply the most practical way of keeping your shop clear of this large volume of debris.
How Dust Collection Systems Work
A dust collection system works by capturing woodworking dust and debris in a stream of air and transporting it through the system's ductwork to a collection area. A dust collector uses a large induction motor to drive a special type of fan called an impeller. The dust collector's 1HP or greater motor and impeller type of fan are necessary in order to generate the large volume of air flow required to move the substantial amounts of dust and debris produced by woodworking equipment.
Ratings and specs for individual dust collectors are listed on the Rockler website in individual product descriptions under the "Details" tab.
Air Flow Velocity and Volume
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). To keep the volume of debris generated by stationary woodworking tools aloft on its way to the collector, the system also has to move a certain (fairly large) volume of air, measured in cubic feet per minute (cfm).
Air Velocity (fpm) and Dust Collection
Experts generally agree that the air speed needed to keep woodworking debris moving through a dust collection system's ductwork is 3500 fpm for main ducts, and 4000 fpm for branch ducts that serve individual tools.
Air Volume (cfm) and Dust Collection
Estimates of the air flow volume levels necessary to adequately handle woodworking chips and dust, on the other hand, vary some from source to source, depending in part on what is meant by the term "dust collection." Higher estimates for a given power tool are likely to represent the air volume necessary to capture nearly all of the dust output from a woodworking tool (including the fine, airborne dust) and can be much higher than the volume necessary for the less ambitious goal of capturing the majority of the bulky chips, large particle dust, and shavings that would otherwise clutter-up your shop floor.
Air volume requirements also vary depending on the debris output of the tool. 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 power tool manufacturers publish minimum cfm requirements for each of their power tools. We encourage you to consult with the manufacturer of the tools in your shop before selecting and designing your dust collection solution. 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.
|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|
|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|
The Relationship between Air Velocity and Air Volume
Simply stated, the relationship between air volume (cfm) and air velocity (fpm) in an air handling system is a function of the size of duct that the air stream is moving through: A stream of air moving at a speed of 4000 fpm through a 12" diameter round duct is transporting a greater volume of air than a 4000 fpm air stream moving through a 3" diameter duct. As a matter of fact, the difference is significant. The 4000 fpm air stream in the 12" diameter duct is moving 3142 cubic feet per minute (cfm) of air volume, whereas the 4000 fpm air stream in the 3" diameter duct is moving only 62.5 cfm.
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, and it must be able to do so while moving the air at the minimum recommended velocity.
Friction is the dust collection system's enemy. As an air stream moves through an air handling system, it rubs up against the surfaces of ductwork, has to round corners, is forced through restrictions, etc. - 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 resultant loss in speed and volume of the air stream.
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, wyes, and T's are primary culprits in building up static pressure losses that hamper the system's performance. Duct size also plays a major role. The static pressure losses in in straight runs of narrow diameter ductwork are far more severe than in comparable runs of a larger diameter duct.
Dust collectors are usually rated to stand up to a certain maximum amount of static pressure. If a dust collector is rated for a maximum static pressure of 12 inches of water (near the top of the range for dust collectors) it will cease to move air at all when the demands of a system's ductwork reaches 12 inches of static pressure. In setting up a dust collection system, one of the main challenges is to design a system that will move air with enough force to overcome static pressure losses and still deliver the air velocity and volume necessary to effectively transport woodworking debris.
Choosing a Dust Collector
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. Unfortunately, a thorough explanation of dust collection design - including formulas for calculating air volume, velocity and static pressure losses - is beyond the scope of this article.
There are, however, a few dust collection "rules of thumb" that are based on the size of your shop and the type of tools in it. Below well offer our picks for dust collection systems ranging from a small portable dust collection solution to a central system for a well equipped two car garage sized shop.
How Dust Collectors are Rated
Dust collectors are designed and rated to produce a sufficient air moving force to capture and move woodworking debris under certain conditions. Nearly all manufacturers publish ratings for individual dust collectors including:
- Air velocity in feet per minute (fpm)
- Air volume in cubic feet per minute (cfm)
- Maximum static pressure (sp)
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 situated farther away from individual machines, making them more advantageous for central dust collection systems.
Affordable, Portable Systems
A portable dust collector is a good option if your priorities are affordability and simplicity. A portable dust collector is moved from machine to machine, keeping it in close proximity of the tool it's servicing and limiting the static pressure losses caused by long runs of ductwork. There's a minimum amount of set-up involved - the dust collector connects to the dust collection port of the tool it's servicing with a short length of flexible hose and a keyed hose clamp.
The Dust Right Wall Mount Dust Collector is an excellent choice for a small woodworking operation where an affordable solution is the goal. With a 650 CFM suction capacity, this compact dust collector handles serious shop messes without cluttering up your workspace. It mounts in seconds with simple (included) brackets. For even more versatility, order a few extra brackets and install them in strategic locations around your shop. Then use the comfortable foam grip handle to move the unit to wherever you happen to need it. With a host of attachments & fittings available, the Dust Right system can give you complete dust collection in a small package with a price to match.
Stepping Up for Better Performance
If your shop is equipped with a number of large stationary power tools, consider stepping up to a dust collection unit rated in the 1100 - 1200 cfm range. Used as a portable dust collection system (moved from tool to tool), 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 dust collector stays in one place in the shop and is connected to the woodworking tools it services with a system of ductwork. A central system has a couple of advantages over a portable system. The central dust collection 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 transfer the dust collector's connection.
Getting the Right Sized Dust Collector
Runs of ductwork, elbows and wyes 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 static pressure losses - with enough air volume and velocity left over to move material.
Basement and One Car Garage Sized Shops
Dust collectors in the 1100 - 1200 cfm range offer an economical central dust collection solution for small shops. Dust collectors in this class are typically rated at a maximum static pressure of 8+ inches of water, making them powerful enough for a hobbyist's basement or one car garage sized shop. Good dust collection system design will go along way in making dust collectors in this class perform well in a central dust collection system.
Two Car Garage Sized Shops
If your shop occupies a space approximately the size of a two car garage, or you own tools with very high cfm requirements, then a moving up to a powerful, 3 HP dust collector is probably your best choice. Dust collectors in this class typically pull upwards of 2200 CFM and are rated at 10+ inches of static pressure. With good system design, that's enough force to pull debris through the longer lengths of ductwork necessary in a large home shop.
Small Professional Shops
If your shop cover's more space than a good sized two car garage, or you frequently have two or more people using machinery at the same time, you may need more than one of the dust collectors mentioned above to do an adequate job. Or you may just need a larger dust collector. Moving up to a 5 HP dust collector will typically get you a whopping 4500+ CFM to keep bulky shavings moving along with plenty of static pressure to overcome long runs of amply-sized ductwork. Along with the increase in power, these production-oriented units typically incorporate larger collection bags to minimize time spent making room for more dust.
Dust Collection System Design and Equipment
In setting up a central dust collection system, good design makes all the difference. Below, we'll help you get the right dust collection fittings, ducting, ports and other dust collection equipment designed to help you get the most out of your dust collection system.
We also recommend more in-depth research. There are a number of excellent dust collection books available. One of our favorites, Sandor Nagyszalanczy's Woodshop Dust Control, has detailed information on best practices in dust collection and instructions on designing a system that will take all of the guesswork out of getting set up.
Dust Collection System Equipment and Design Tips
Use rigid metal pipe and metal fittings for longer runs of ductwork. Air travels smoothly through rigid spiral pipe, reducing the static pressure losses in the system and increasing the system's efficiency. Metal fittings designed to reduce friction in air handling systems greatly increase the efficiency of central dust collection systems.
Use flexible hose designed for dust collection. Using flexible hose that's not designed for the dust collection can greatly reduce the efficiency of the system. Black polyethylene dust collection hose is designed to produce a minimum amount of static pressure loss and to stand up to the vacuum pressures produced in dust collection. Clear, wire reinforced dust collection hose has the added benefit of making clogs and buildups of debris in the system easy to spot and correct.
Use PVC fittings to connect runs of flexible hose. When it is necessary to connect separate pieces of flexible hose, use PVC dust collection hose fittings. PVC elbows produce far less static pressure loss in situations where an abrupt change of duct direction is required than a sharp bend in a run of flexible hose. PVC Y-connectors and T-connectors make quick and easy work of setting up branch ducts. Dust collection splicers make it possible to connect straight runs of hose, and dust collection couplings allow two or more fittings to be joined directly together.
Isolate each woodworking machine in the system with a blast gate. In most cases, to achieve adequate dust collection at individual machines, you will need to use either automatic or manual blast gates to shut off the air flow to other machines that are not in use.
Automatic blast gate systems are an extremely convenient solution. Both the Ecogate Blast Gate System and the JDS Automated Blast Gate System open the correct blast gate and turn on the dust collection system when you flip the power tool's switch. An added feature of automatic systems is that they prevent you from forgetting to turn on the system and open the correct gate.
For a more budget economical solution, manual blast gates will work perfectly well. Rockler offers plastic blast gates designed for use with flexible hose and PVC fittings and metal blast gates that can be used with either flexible hose or metal pipe. Blast gates designed specifically for use with spiral metal pipe are listed along with the spiral pipe and fittings offer.
Outfit you tools with dust collection ports, hoods. The dust collection performance for many open stand table saws and jointers can be greatly improved with the installation of a dust collection hood. The hoods can be easily adapted to fit most contractor-type table saws and 6' and 8' jointers and are designed to work with 4' dust collection hose. For router tables, use the universal dust port. The universal dust port's flange attaches with screws and can be used with 2-1/2' dust collection hose or 2' shop evac hose.
Use universal ports for tools with no direct dust collection port. For tools with no direct dust collection attachment, or to enhance primary dust collection, use a tabletop dust fitting or a free-standing universal dust collection port.
Use quick release connectors. If you are setting up a portable dust collection system, quick release connectors such as keyed hose clamps and quick disconnect dust collection fittings will make moving your dust collector from machine to machine quick and easy. For stationary systems, they will make set-up, cleaning and inspection much less time consuming.
Use the right size of reducer or adapter to step down hose diameter. In general, it is better to use large diameter hose for longer runs and step down to the correct size for machinery dust ports as close to the machine as possible. Using the wrong-sized or makeshift adapters to step down hose diameter creates unnecessary drag on the system. Reducers designed for use with dust collection hose make transitions between hose diameters as smooth as possible. The universal duct adapter allows transitions between any combination of the most common hose diameters. The dust collection hose adapter allows 4' hose to be connected to most standard 2-1/4' bench top tool dust ports.
Ground your dust collection system's ductwork. Static electricity build-up in your system's ductwork presents a fire hazard and can produce an electric shock on contact. When properly installed, a dust grounding kit will greatly reduce the static electricity build-up in your system's ductwork.
Increase your system's chip holding capacity with a dust collection separator. Dust collection separators increase the waste holding capacity of your dust collection system by separating out larger sized chips and shavings before they reach your dust collector. They also reduce wear on your dust collector's blower assembly caused by collisions with large debris particles.
Now that you understand the importance of dust collection and have the basics down, you're ready to get started building a dust collection system that's appropriate for your shop. And when you're finished, you may be tempted to rest on your dust-free laurels. But not so fast! In nearly every case, getting control over the bulk of the debris in your shop is only half the battle. You'll also need to consider the minute dust particles that your dust collector can miss. In "Dealing with Fine Woodshop Dust," you'll learn the risks of letting fine dust run wild, and what you can do to solve the problem.