Hello, welcome to this Timbecon sponsored article about dust collection.
Dust collection can be a complex undertaking for many woodworkers. So, to help you out, we have taken what we know and created this dust collection guideline written in two parts:
- Part 1 – The Dark Arts of Dust Collection
- Part 2 – Designing and Building Your Own Dust Collection System
Part 1 focuses on the conceptual elements of designing a system and the common gear you will need to build one. Part 2 is the practical application of the items discussed in the former, breaking the process of designing and building your own system down into six straightforward steps.
Please enjoy!
Why you need dust collection system
Dust collection is critical. And must be at the foundation of every woodworker’s shop. Yet designing and building your own dust collection system can be a confronting challenge. This is because dust collection is a science that rests upon some complex mathematical concepts. In addition, there is no one system solution for every woodworker. As a result, a properly designed dust collection system is often relegated to the too hard list.
This is a real problem. No doubt you know why. Yet just to be clear, dust particles are dangerous for your health. If you do not manage dust, particularly air borne dust, it can enter your lungs and cause diseases including occupational asthma and lung cancer. If this wasn’t enough, dust is also bad for your machines. Clogging them up and shortening their useful lives. But enough of the fear mongering, this article is about providing a dust collection solution and not scaring you off woodwork for ever.
Dust collection is fun
On the upside, building a dust collection system can be a fun project. It may test your mathematical skill a little. Your workshop may be in turmoil for a week. However, if you follow this guide and do the work, you will emerge from the end of this experience with fully functioning dust collect collection system that will protect you and your machines.
A couple of important notes
Before we start, a couple of notes. This article should be viewed as a guideline only. It is suitable for enthusiast and small production scale workshops only. Industrial systems should be designed by an industry professional. Also, your dust control systems MUST be grounded to avoid a build-up of static electricity in the ductwork. Static electricity can cause sparks within the system that could lead to a fire. If you are unsure about whether your system is adequately grounded, consult an electrician.
Ok, enough rules. Let’s start by looking at some of the key concepts your system will be designed upon. And review some key pieces of equipment that will make your system work.
PART 1 - THE DARK ARTS OF DUST COLLECTION
Behind every dust collection system a battle rages. A battle between desire, cost, fear and ignorance. Assuming you suffer from at least one of these traits, let’s start from the beginning.
What is a dust collection system?
A dust collection system is whatever means you use to manage dust in your workshop. For some this is a dustpan and a broom. For others it is a sophisticated network of ducting and large vacuums. Whatever the system you have, your dust collection system should be suited to the type of work you do, and it needs to capture as much dust as possible.
What is dust?
Dumb question, right? Dust can be either fine particle or large shavings. The point here is the size of the particles. Particles less than 10 microns in diameter, in other words 0.01 millimetres, are dangerous for your health. They can become lodged in your lungs and cause disease. A good dust collection system must be able to collect and eliminate these fine particles as much as possible.
Meet Alex
Alex is an enthusiast woodworker. Alex likes to build boxes, in particular cases for speakers and retro synthesisers. Alex works in a single attached garage and has two machines – a bandsaw and a combination thicknesser / planer. Alex also has a router table great for making beadings and machining long trenches for fitting panels. Alex dreams of one day buying a table saw - space and spouse permitting. Alex lives in townhouse so controlling dust is very important, not just for health reasons, but for preventing dust from leaching into the house through the internal door.
Alex’s Challenge
Alex needs a system that controls dust in three ways. Firstly, to remove bulk waste from the operating machines as efficiently as possible. Secondly, this bulk waste must be shipped to a ‘hopper’ where it may be stored until it can be disposed of. And thirdly, it must collect any fine dust that managed to escape while being collected in parts one and two. Fine dust is the biggest enemy for Alex. This is the most dangerous form of dust, particularly when it becomes airborne in a small and enclosed space. It is also the dust that seeps into the main house through the gaps around the internal door. This upsets Alex’s partner considerably, another pathway to certain death.
What are the main parts of a dust collection system?
A typical dust collection system such as Alex’s has four main parts.
1. Machine dust ports
To start there are the machines themselves, the source of the dust. Each machine will have a dust port. The dust port is where the waste generated by the machine is expelled, usually in the form of a short pipe section. Dust ports vary in size from 50mm to 150mm in diameter, sometimes larger on industrial machines. Most machines and many electric hand tools these days have dust ports. If you are considering buying a machine without a dust port, I suggest you keep looking.
2. The Ducting
Ducting is the hose that connects to your machines dust port. It is through this hose the dust your machine generates travels through on its way to the dust collector and hopper. Ducting, like dust ports, comes in various diameters and is made from different materials including metal, PVC and plastic. Ducting is usually suspended overhead in the workshop to minimise clutter on the workshop floor. We will discuss ducting in more detail below.
3. Ducting Fittings
Ducting needs fittings to join it all together, a bit like plumbing in a house. You need components to get around corners (90-degree bends). To combine two lines into one (Y connectors). And fittings to hold the duct in place (hose clamps). We will discuss ducting fittings in more detail below.
4. The Dust Collector
The dust collector machine is the heart of the system. These are basically a large vacuum that sucks air through the ducting, dragging the dust with it out of your machine into the dust collector hopper. The dust collector has three main parts - the impellor, the hopper and the air filter. The impellor is a spinning fan that creates the negative air pressure and therefore the vacuum effect. The hopper is where the larger dust particles and shavings sucked into the collector are separated to and stored. The air travelling through the dust collector is then pushed out through the filter where the finer dust particles are collected before the air re-enters the workshop environment.
What is CFM?
For a dust collection system to work, the system must enough “SUCK” to pull dust through the system. The amount of suck is usually expressed as the CFM (Cubic Feet per Minute). CFM is a relative term, based upon a variety of environmental conditions and mathematical equations. For you and Alex, it is the amount of airflow required to move through your dust collection system to make it work properly.
To calculate the CFM or airflow required for your dust collection system. Start by measuring the diameter of the dust port on your machine and then compare it to Table 1 below.
| Dust Port Diameter | 25mm (1") | 55mm (2") | 75mm (3") | 100mm (4") | 125mm (5") | 150mm (6") | 175mm (7") | 203mm (8") |
|---|---|---|---|---|---|---|---|---|
| CFM Required | 24 | 98 | 220 | 395 | 615 | 884 | 1203 | 1570 |
Table1. Dust Ports and Relative CFM Required
This table says, if you have one machine with a dust port of 100mm, your system needs to generate 395 CFM to work. If you have two machines both with 100mm dust ports, you simply add the two CFM’s together, 395 + 395 = 790 CFM. You therefore require 790 CFM of suck for your two 100mm dust port machines. You can use this simple methodology to calculate the total CFM required for your whole system.
Alex has three machines. Both the bandsaw and the combination machine have 100mm dust ports. The router table has a 55mm dust port on the fence. The CFM Alex’s system requires is 2 x 395 + 98 = 888 CFM.
CFM is also used to measure the amount of suck your dust collector can produce. Most enthusiast dust collectors produce between 600 and 1200 CFM at the machine. Information regarding dust collectors and their relative CFM’s is available on the Timbecon website.
What is static pressure?
Static pressure is all about friction. When air moves through your dust collection system, friction slows it down. Friction is created by the air interacting with the dust being carried along, and the ducting it is moving through. The total amount of friction created is referred to as the static pressure (SP). It is often measured in inches of water column pressure (WC) or in Pascals. Static pressure increases as the air's mass and speed increase.
How does static pressure affect your dust collection system?
The amount of static pressure your system generates is directly related to the amount of ducting and ducting components you incorporate into the design. In other words, if you have a big complicated system with lots of twists and turns and miles of ducting, you will have high static pressure. If the effect of static pressure within your system is too great, then the airflow will be insufficient to move the dust within it rendering your duct collection system useless.
The rule of thumb is to keep your system compact and simple. Alex’s workshop is small. Dust doesn’t need to travel too far to reach the collector so minimal ducting is required. Alex has only three machines. Not a lot of complicated bends and joins are required so the air flow moves freely without much hinderance. Provided Alex keeps the system compact and simple, static pressure may not be a major problem and so no allowance for static pressure is necessary.
If your workshop is larger and you have more machinery than Alex, you may need to account for static pressure when designing your system. Refer to Table 2 below for guidance on calculating the potential static pressure of your system.
| Component | Reduction in CFM | Outcome |
|---|---|---|
| 1000mm of flexible 100mm PVC spiral ducting | 5 – 10% per metre | For every metre of PVC spiral ducting, you lose 5-10% of total CFM |
| 90-degree bend connector | 3 – 5% per bend | For every 90-degree bend you add, you lose 3-5% of total CFM |
| Y Piece connector | 1 - 2% per bend | For every Y piece connector you add, you lose 1-2% of total CFM |
| T Piece connector | 3 – 4% per piece | For every T Piece connector you add, you lose 3-4% of total CFM |
Table 2. Relative Static Pressure Loss
As an example, imagine you have a thicknesser with a 100mm dust port requiring 395 CFM of suck to function. You place the duct collector ten metres away and use 100mm PVC spiral ducting to connect the two machines together. If you dust collector generates 600 CFM at the machine, by the time the dust has travelled through ten metres of the ducting the CFM has reduced by as much as fifty to one hundred percent. At the thicknesser dust port, your 600 CFM dust collector is now only drawing at somewhere less than 300 CFM - not enough to service your machine. Rule of thumb reminder –keep your duct collection system compact and simple.
DUST COLLECTION EQUIPMENT
We have discussed some of the key concepts that underline dust extraction system design. Let’s now take a closer look at the actual dust collection equipment.
Dust Collectors for the Enthusiast Woodworker
Shop Vacs
Shop Vacs are a common sight in many workshops. They are very versatile equipment particularly for cleaning, dust extraction for power tools and smaller benchtop styled machines. They are not designed to remove dust or shavings from larger machines such as table saws and jointers.
A shop vac would be very useful in Alex’s workshop. Not only to vacuum the floor and shelves, but it would also be more than adequate to manage dust created by the router table.
Advantages – versatility and movability
Disadvantage – designed for smaller tools, not suitable for larger machines
Single Stage Dust Collectors
The most economical and most popular dust collectors are single-stage models. Single stage dust collectors can be easily identified as they have an upper bag that is the filter, and directly below another bag that is the hopper. Single stage means that dust is sucked through the impeller into the collector and dumped into the lower bag. Simultaneously the air is forced back out through the upper filtering bag back into the workshop.
Single stage dust collectors feature 1HP to 3HP motors. In general terms, the size of the motor will determine the CFM of the collector. When researching dust collectors, Timbecon has the CFM rating for each model available on our website.
Single stage dust collector upper filters can become clogged quite quickly with fine dust. Clogged filters will restrict the airflow through the system, reducing the CFM. The filters must be cleaned regularly to maintain the efficiency of the system.
Being affordable and compact, a single stage dust collector is certainly a good option for Alex. The amount of cleaning these dust collectors require may be a problem. For Alex is seems counter intuitive to purchase a dust collector that requires constant cleaning to be effective.
Advantages – affordable, mobile and easy to set up, filter air to 5 microns
Disadvantages – filters must be cleaned regularly, emptying the hopper is a messy job
Two Stage Dust Collectors ‘Cyclones’
Unlike a single stage collector, dust does not flow through the impellor in a two-stage dust collector. The motor and impeller sit on top of a cone shaped chamber called the cyclone. When operating, air flows into the collector through a port. This moving air, with help from internal baffles, creates a cyclonic vortex that draws 99% of dust particles down into the chamber for collection. The air flow then travels out again through the main filter, finer particles are collected by the main filter on exit. As air does not move through the impellor, and 99% of dust and debris is removed before it reaches the filter - this means cyclone dust collectors operate very efficiently with continuously high suction. Thus, cyclone dust collectors do not require a high CFM to be effective.
Cyclones usually feature pleated filters. This style of filter is very easy to clean. And because 99% of the dust is removed before it reaches the filter, these filters will enjoy a long-life span. We will talk more about the types of dust extraction filters below.
Being easy to clean, a cyclone dust extractor is a good option for Alex. Though price may be a problem, particularly while saving for that table saw.
Advantages – efficient, easy to empty, filter dust particles to 1 micron
Disadvantage – less affordable
Overhead Room Filters
When you come into your workshop each day, do you notice a fine layer of dust on the surfaces of your machines? This is atmospheric dust that has settled overnight. When dust is expelled from you dust collector it contains a small amount of very fine dust that will stay suspended in the atmosphere of your shop for hours. Tasks such as hand sanding will also add to the atmospheric dust in your shop. This suspended fine dust is easily inhaled and is dangerous. To control atmospheric dust, add a Room Cleaner to your workshop.
Room cleaners are compact units that you suspended from the ceiling. Using a remote control, you can switch it on and leave running as long as required. They continuously pull air in and through a filter removing dust particles to one micron. Consider them as life insurance.
For Alex this is a no brainer. These items are inexpensive and will help minimise that fine dust that always seems to seem into the inside hallway. One challenge though, how / where to plug it in?
Advantages – affordable and can clean localised atmospheric air to one micron
Disadvantages – cumbersome to install, require regular cleaning at height
Types of Filters
As discussed above, there are two main types of dust collection filters, needle bag and pleated.
Needle Felt Bag filters
Needle bag filters are common and are usually supplied standard with most single stage dust extractors. These fabric filters are economical, and able remove up to 95% of dust particles to 5 microns. Bag filters require cleaning regularly as they tend to clog with dust particles that will impede the flow of air through the dust collector, reducing the CFM of the system. Cleaning bag filters is a messy task that must be completed regularly.
Alex is not keen on the bag filter at all. 95% of dust sounds like a lot, yet the 5% of dust that remains is a real problem. That’s the dust that is most harmful, and the dust that gets inside the house.
Advantages – economical
Disadvantages – only filters dust particles to 5 microns, cleaning is messy and required regularly
Pleated Filters
Pleated filters are made from a type of folder paper installed within mesh cylinder. They feature a built-in cleaning mechanism that makes cleaning the filter very easy, helping to maintain the maximum CFM of your system. If maintained correctly, a pleated filter will work perfectly for many years.
Pleated filters are very effective removing dust particles to 1 micron. This means they are good for your health. Pleated filters are usually supplied standard on cyclone dust collectors. They are also available in a variety of sizes and may be retrofitted to most single stage dust collectors.
Alex is set on a pleated filter, being easy to clean and 99% effective are both key advantages. The challenge will be affordability.
Advantages – filters dust particles to one micron, very easy to clean
Disadvantages – less affordable
Ducting and Fittings
To build your ducting system you and Alex will obviously need ducting and a whole bunch of fittings. The list of fittings available is very extensive so we will just focus on a few of the key items for this guideline. Visit the Timbecon website to see the full range of dust fitting available.
Ducting - flexible spiral PVC
Flexible PVC ducting is very common throughout the workshops of Australia. It is relatively inexpensive, versatile, durable and easy to install. Many woodworkers just own one long length of it, attaching it to the machine in use at the time. A spiral wire runs through the ducting that makes the PVC ducting so flexible and durable. However, this wire creates a ribbed effect along the inside of the ducting. This means PVC ducting is very prone to static pressure and so long sections can reduce the CFM of your system significantly as identified in Table 2 above. To maintain the CFM of your system, the application of flexible PVC ducting should be minimised as much as possible.
Advantages – affordable, flexible and easy to install
Disadvantages – creates static pressure through friction
Metal Ducting
Metal ducting on the other hand does not create high levels of static pressure. The interior of metal ducting has a smooth finish that reduces friction from air flow, in turn minimising static pressure. The static pressure rule of thumb for metal ducting is a one percent loss in CFM per metre, compare that to flexible PVC. Metal ducting can be expensive and difficult to install. Metal ducting is usually beyond the budget of most enthusiast woodworkers.
Advantages – durable and produces minimal static pressure
Disadvantages – expensive and lacks flexibility
Ducting - PVC Plumbing Pipe
Some woodworkers choose to use plastic PVC plumbing pipe as ducting. Afterall, it is affordable, available everywhere and features a super smooth frictionless interior surface. PVC plastic pipe has gained a reputation for creating static that can create sparks and lead to a fire. Fires created by PVC pipe are very rare, in the 25 years I have been a woodworker I have never seen a single example. Yet to safe and not sorry, if you choose to include PVC pipe in your system - ground it well.
Advantages – affordable, easy to install, minimal static pressure
Disadvantages – potential fire hazard
Fittings – bend connectors
Bend connectors generally speak for themselves, so we won’t go on about them too much. Essentially, they are used to determine the course of your ducting or to get around obstacles. Keep in mind, every time you add a bend you increase static pressure.
Fittings – Y Piece and T Piece Connectors
Y and T piece connectors are available in a few different designs. Generally, that are used to combine two separate lines into one line. They are also available for combining multiple lines into one. Some Y piece connectors also act as a reducer, combining a 100mm line of ducting into 50mm.
Blast Gates
If you have multiple machines, the combined required CFM may be larger than the capacity of your dust collector. In this situation you can use blast gates to manage the air flow through your dust collection system and preserve your operational CFM. For example, imagine you have two machines that require 500 CFM each to operate, together that’s 1000 CFM. Yet your dust collector only offers 600 CFM. If both dust ports of the machines are open, you do not have enough suck for the system to function properly. To resolve this, you can install a blast gate on each machine. The blast gates may be opened or closed so only dust is drawn from one machine at a time, reducing the required CFM to 500. Well within the capacity of your dust collector.
Hose Clamps
When you build you system, you want all the joins between ducting to be airtight as possible. Hose clamps are an excellent way to fix ducting together and to machine dust ports for an airtight seal. Simple to use, and affordable, don’t forget to add them to your dust collection shopping list.
Part 1 – Conclusion
For poor Alex all this is a lot to take in. Particularly the array of fittings and accessories available. Please go on and read Part 2 “Designing and Building Your Dust Collection Systrem” where we will explain to you and Alex a practical way of how to put all this together. Firstly, by showing how to design a system suitable for your workshop. Then working out what equipment and fittings you guys will require. Calculating the CFM required whilst accounting for static pressure. And finally, building it!
See you then.