Cyclone and Dust Collection Research


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Dust Collector Cartridge Conversion

  1. Challenge

    Hey! I already am in enough trouble with the family for spending so much on woodworking tools. Can I convert my existing dust collector to something safer without breaking the bank?
    Humm... Don't want much do you? Putting on my shop apron..

    The bottom line here is most dust collectors will not move enough air for good fine dust collection. That means any woodworking indoors will quickly build a dangerously high level of the fine invisible unhealthiest dust. As a result, what most of us should do if we cannot afford at least a 3 hp dust collector or 5 hp cyclone is put our dust collectors outside with no air returned into our shops. We also should work outside and wear a good mask while working. If we work inside we should wear our mask and run a strong fan in a side doorway with a larger door or window open not just when we work, but for a half hour after making any dust.

    Just about any small shop dust collector with a real airflow of 450 CFM will do a superior job of collecting chips and keeping our floors clean. If you look at the air tables, in spite of small shop vendor advertising it really takes at least a 1.5 hp dust collector with 4" duct to move this much air. Unfortunately, going after the chips does not protect your health or the health of those close to you. The National Institute of Health (NIH), OSHA, and similar organizations in countries throughout the world agree that the fine wood dust particles that go right through most small shop dust collector filters, including fine filters, are unhealthy with long-term exposure known to cause sensitivity in almost everyone. Many develop more serious problems including asthma, emphysema, allergic reactions, polyps, and even cancer. Government regulations long ago recognized that chip collection does not protect workers amply, because ongoing medical studies show those who work in shops with good "chip collection" still have such high long-term exposure to fine wood dust that almost all eventually become ill, some seriously. We now have government air quality standards to protect workers.

    Small shop woodworkers must fend for ourselves because we have no standards or government protections. The belief that small shop woodworkers receive little exposure compared to professional woodworkers is wrong! Testing in shops using the same tools used by small shop woodworkers shows five to twenty times the dust levels found in most commercial facilities. The reason is most commercial facilities put their cyclones and bag filter systems outside where most of the finest dust just blows away instead of building in our shops to very dangerous levels. My own shop with cyclone and fine filters looked great with almost no buildup of dust. Unfortunately the fine filters I used created a false sense of security because these filters passed most of the fine near invisible dust. Trapping my shop air inside let that fine dust that lingers a long time build to dangerous levels. Any airflow from walking around to turn on my tools launched that fugitive residual dust airborne again and again. With my shop connected to my home, the medical air quality testing I had done showed my shop and my home severely contaminated. That same testing also showed my tools blew the finest dust all over and my expensive upgraded fine filters blew the fine unhealthiest invisible dust right through. My clean looking shop tested at over the government maximums in terms of total weight of suspended dust which is fifty times worse than the EPA allows in commercial facilities subject to air quality testing. The testing I had done also looked at suspended particle counts, and those test results were scary. The finest particle counts in my shop were over 10,000 times those typically found in large commercial facilities that blow their fine dust away outside. Clearly my tools launched the fine dust, my dust collection system failed to collect the fine dust, and the fine dust blew right through my too open filters. Worse, trapping that dust inside let it quickly build to make the air in my shop dangerously unhealthy! Although my inspector said mine was one of the cleaner shops tested, at these levels, just like most other small shop woodworkers that trap our dust inside, we often receive more exposure to the most dangerous fine 2.5-micron and smaller dust in four hours of woodworking than a large facility professional gets in a year of full time work. If you do not think these finest lightest particles are anything to worry about, you might start with my Medical Risks information. Or, you can read over the 47 million references that come up when you do a Google search on "PM health risks". Sadly, almost all close to woodworks with dusty shops also receive too much exposure. With the government maximums now under fire for causing most to eventually develop dust related health problems, this creates a serious concern for us. I strongly suggest doing the homework to make an informed decision on the potential risks.

    Many wrongly think all you really need to protect yourself from fine wood dust is a good mask. A good mask only protects you while working. Few leave their masks on long enough. Using an air cleaner or even a modest sized exhaust fan takes about six hours to clean your shop air amply to take off that mask. Few also only put our masks on when doing dusty work not realizing that as soon as we turn on our tools, dust collection equipment or use our air compressors we immediately launch previously made dust back into our shop air. Because fine dust lingers for six months or more before breaking down or getting blown away, it just builds and builds in our small shops unless we figure out how to get rid of it. It travels in any shared air to go into our homes and offices, plus gets carried on our hair, skin and clothes to contaminate our vehicles, offices, and homes to affect all close to us including our pets for months. The only effective ways to control fine dust is to blow it away outside or provide good fine dust collection. Our only other safe alternative is to work with a dust mask on, preferably outside! See my Doc's Orders for specific recommendations. A good strong fan blowing out a side door with door or window open across your shop will clear most shop air in about a half hour enough to take off your mask.

    To get good fine dust collection takes far more work and expense than chip collection. Normal room air currents will blow the fine dust away from our larger stationary tools unless we remake our tool hoods to control and capture all fast moving air streams, surround our tools with a "bubble" of air that moves at least 50 feet per minute (FPM), and then get rid of this dust. To build this huge low pressure "bubble" we must move about three times more air than it takes to just do good chip collection. This requires a bigger blower, typically a 2 hp and larger dust collector or 5 hp and larger cyclone. If you use a short 6" diameter duct and vent through clean new large cartridge filters you can just barely get enough airflow through the larger Delta and Jet 1.5 hp dust collectors. All other makers needed at least a 2 hp blower. To get rid of the dust, those units need to be put and kept outside with no air coming back into our shops.

    Unfortunately, many like me cannot put our dust collectors outside because it is illegal, makes too much noise for the neighbors, or is not practical to blow our heated or cooled air away outside. For us, we need to provide better air filtering. My doctor recommends only using independently certified 0.5-micron or better fine filters and blowing out our shops after major dusty operations to get rid of any accumulated dust. He says about the only way to get ample filter area is to use a cartridge filter. That cartridge filter should provide roughly one square foot of filter area for every 2 CFM if you use a typical paper polyester blend certified filter. If you use the more expensive thicker all polyester or special fine fiber blends, you can get by with as little as one square foot of filter for every ten CFM to do the filtering, but will have too frequent cleanings if you choose to use filters this small.

  2. Warnings
    1. Traditional bag type small shop dust collectors are more dangerous than if we went back to brooms and dustpans because these units are dust pumps that recycle the most hazardous particles.

    2. Many woodworkers wrongly believe, as I once did, that fine filter bags and cartridges would be enough. I bought a set of expensive fine filter bags and was proud of myself thinking I had done well, but all in my shop continued to be covered in fine dust. An existing lung injury from ages ago in the military combined with that heavy dust exposure to make me very ill. While recovering, I did a lot of homework and was pretty unhappy to find that many of these so called fine filter bags were rated by the makers. They could claim any level of filtering they want by simply clogging them with so much dust they won't pass air. Three different universities tested my fine filter bags. Each found that unlike cartridge dust filters built for industrial use with certified filtering capacities right out of the box, just like most older style small shop dust collector bags, my fine filter bags passed the same 30-micron sized particles all day until they were so caked with dust they would barely pass air. With further homework I found a few good filter bag makers. You can call up American Fabric Filter and order up a big top replacement bag then get some thick plastic bottom bags from ShopSmith for about $8 and a nice cam action bag clamp to seal and hold that bag in place from ShopSmith part number 518393 plus tax and shipping.

    3. The good quality bags that actually provide their rated level of filtering are still not a good solution. Like cartridges, fine filter bags provide better filtering and much more airflow by using much finer filtering threads. Unlike cartridges, few bag sets have more than 30 square feet of surface area. We need one square foot of filter for every two square feet of airflow. A typical 2 hp dust collector that moves 800 CFM then needs about 400 square feet of filter. In other words a 30 square foot filter or even the 120 square foot cartridge filter is far too little area. Filters with too little area will clog almost immediately when used with a dust collector or cyclone because too much dust goes into the filter. Also, cleaning wears out our filters making them more porous so they pass more and larger dust particles. Rather than figure out a way to avoid so much going into our filters, most small shop filters are wide open meaning 10 to 20-micron filters that freely pass most of the fine invisible dust. Not wanting to constantly clean and replace my expensive fine cartridge filters is what inspired me to build my much better separating cyclone.

    4. Although a number of small shop vendors now offer cartridge filtered based dust collectors, my hopes for these units providing significant help collapsed. Testing shows almost all small shop dust collectors and cyclones come with 10 to 20-micron filters that get advertized as anything from 0.5-microns to 2-microns. What they forget to say in their ads is they can claim any level of filtering they want provided they also don't give us their airflow at that filtering level. Even a large open screen can be turned into a 0.5-micron filter if we pile on enough dirt and rock. It is the under 10-micron stuff that causes the most health damage. In short, almost all small shop fine bag filter and cartridge filter equipped dust collectors and cyclones simply allow most of the finest unhealthiest dust to pass right through. Rather than play this game ASHRAE sets the industry standard to test all indoor filters when clean and new.

      The fancy paddles, flappers, and other cleaning systems offered on cartridge filtered dust collectors are there because these units also have a basic design flaw. They allow everything to blow right up into the filters. This means that the cartridge filters quickly plug and need constant cleaning. That tradeoff appeared acceptable to me at first until I continued my testing and found the cleaning quickly wore out the filters and the high velocity chips poked holes in the cartridge filters. With thousands of new larger holes after every use and the cleaner making that even worse, soon these fine filters end up passing all that the old dusty bags passed. You can tell when you have a problem when your shop again has a coating of fine dust everywhere. These units either need a trashcan separator, a baffle (see Phil Thien's baffle design) or a fine screen to block these hits and much finer 0.5-micron filters before they get my blessings. Trying to protect a cartridge filter with a traditional trashcan separator does not work useless unless you strangle your collector airflow with 4" pipe. If you use the 6" ducting and 800 CFM that you need to get the finest unhealthiest dust, the airspeed will be so high it will scour the trashcan separators clean of all but large blocks. It takes a trashcan separator that is about 5'2" in diameter and 7' tall to handle 800 CFM.

    5. In the late nineties John Dillbeck spotted the idea of using an extended inlet to reduce internal cyclone turbulence and improve fine dust separation in an obscure cyclone article. He shared that information on the Badger Pond Internet woodworking forum and not long after many small shops began modifying their cyclones and dust collectors to improve separation efficiency and use less power because they were not generating so much internal turbulence. Someone coined the misnomer "neutral vane" and the extended inlet has been called this ever since. Although adding a neutral vane improves airflow it does little to help with fine dust separation.

      Typical early small shop cyclone designs are downscaled versions of the large commercial cyclones we see outside most woodworking facilities. These cyclones use very high internal turbulence to do a great job to knock the fine dust from the heavier dust and chips, then just blow that airborne dust away outside. Traditional cyclones separate off about 95% of the wood dust and chips by weight then blow the remaining 5% airborne dust outside. The dust left after blowing away the airborne dust is often used in small shop magazine and vendor tests to let vendors claim 99% and higher separation efficiencies. When tested with real dust that still contains the airborne dust most small shop dust collectors and cyclones get roughly 0% (zero) fine dust separation efficiency. This puts all the airborne dust into the filters. Using a traditional cyclone designs with a fine filter is foolish. It only takes about a half pound of fine airborne dust to badly clog a big fine filter, yet woodworking makes about five pounds of airborne dust out of every one hundred pounds of sawdust and chips. This means every ten pounds of sawdust requires a filter cleaning. If you cannot blow the air outside, you really need a much better cyclone separator to protect the filters, minimize cleaning, and maximize filter life.

      Wanting more separation efficiency I went back to the swirl tube physics, came up with a better cyclone design that was far more efficient. It provides much better airborne dust efficiency at roughly 99.9% down to 4.7-microns, plus uses less energy as it has a smoother internal airflow meaning uses less horsepower. I shared my research and designs on these pages. Now most small shop and even some large commercial vendors provide a neutral vane or some of my later suggested enhancements, but as of late 2011 almost all small shop dust collectors and cyclones still send most of their airborne dust into their filters. Too many small shop cyclone vendors now avoid seeming to have a problem by simply selling very open filters that freely pass the dust their systems cannot separate. One vendor actually claims their design is so efficient that most only need to clean the filters a couple of times a year. My particle testing showed that vendor's filter was so open it freely passed 30-micron and smaller particles.

    6. Upgrading to a cyclone can be expensive, so many want to add a cartridge to their existing dust collector to keep from recycling the unhealthiest fine dust. Stopping fine dust recirculation helps, but is generally not enough to make your shop air safe because most dust collectors move too little air to capture much of the fine dust as its source. Careful engineering and testing shows most of our larger small shop sized tools need hood upgrades and a real 800 CFM to effectively capture the fine dust as it is made to meet OSHA recommended air quality and a full 1000 CFM to meet the EPA, medical and European air quality standards for woodworking shops. Although many dust collectors claim far higher CFM output, the vendors make their ratings with no hose, no duct, no bags, no filter, and often a special hyperbolic inlet to maximize airflow. Under real working conditions, most small shop dust collectors provide about half their advertised airflow, far too little to effectively capture the fine dust at its source. Except for the Delta and Jet 1.5 hp, none of the dust collectors I tested moved the minimum 800 CFM with anything less than a 12" diameter impeller and real 2 hp motor and it takes a full 3 hp motor with 14" diameter impeller to move the 1000 CFM we really need for good fine dust collection. The Jet and Delta 1.5 come close because they use more efficient larger impellers and better engineered blower housings than the other units I tested. Unfortunately, getting a 2 hp or even 3 hp dust collector does not ensure moving the needed CFM. A number of the 2 hp collectors I tested including the Harbor Freight 2 hp (Which is really a 1.6 hp unit), Grizzly 1029 2 hp, Reliant 2 hp, King 2 hp, and PSI 2 hp dust collectors failed to move 800 CFM due to small impellers, poor blower designs, and restrictions. So, at a minimum you need 6" blower inlet, 5" blower outlet and 11.5" diameter or larger impeller to get at least 800 CFM. Although you can significantly reduce the fine dust in your shop air with a cartridge filter upgrade, you are not going to collect that fine dust at the source unless you have a big enough dust collector and upgraded hoods.

    7. With it only taking the slightest breeze to move fine dust, many don't understand why collecting fine dust takes double the airflow needed to collect the chips and sawdust you can get with a broom. Airspeed when blowing falls off slowly as the air travels away. A stream of air can carry many feet before its speed falls so much that it will no longer move fine particles. This is not the case with sucking, because sucking pulls from all directions equally. This causes the airspeed to fall off at 4 times pi times the distance squared which is the area formula for a sphere. We already know how this works. Think about using a shop vacuum. Just a few inches away from a vacuum you can barely feel any air movement at all. To test this wet a finger and see how far you can move it from your lips and still feel blown air. Wet it again and see how far away you can feel sucked air. Most of us can feel our blown air as far as we can reach, but no longer feel sucked air just a tiny distance from our lips. The result is blown air can launch and keep fine dust suspended in our shops air for hours, but to get rid of that airborne dust we have to move a huge amount of sucked air. So in short we need good hoods to control the fine dust before it escapes then move lots of air to capture it before our normal shop air currents blow it all over.

    8. The more air a blower impeller pushes, the harder the blower motor works. Trying to move too much air can easily over stress your blower motor. The increased airflow from adding a cartridge filter and larger ducting can potentially burn up a dust collector motor from working too hard trying to move too much air. Cartridge filters have so much surface area that the resistance can fall too low. This can double total airflow. Likewise, moving from smaller to larger ducting can also move so much air we can easily burn up our dust collectors when shifting from 4" to the 6" diameter ducting needed to move enough air at our larger machines for good fine dust collection. I recommend you use an amp meter before and after adding a cartridge to ensure the motor does not draw too much current and burn up. Adding more ducting or a partially closed blast gate before the blower inlet can cure this problem.

    9. Not every dust collector can be upgraded by just adding a cartridge. I have not heard of anyone having a problem adding a cartridge filter to 1 hp and smaller dust collectors. I've heard that many have successfully added cartridge filters to the 1.5 hp and larger collectors, but almost all have problems. The issue is almost all dust collectors come with a fairly inefficient or just plain no separation ring and poor inlet design. This allows far too many heavier chips and volume of dust to blow up into our cartridge filters. Not only do the chips punch holes, the chips and sawdust gets stuck in the pleats creating a cleaning nightmare. All can be fixed by replacing the bag tree ring with your own separator.

  3. Basics

    Just adding a cartridge filter or even a cyclone is not enough. You also have to do a number of other things or your tools will still keep your shop filled with very unhealthy levels of fine dust exposing you and those close to you. To collect the fine unhealthiest dust you also need better tool dust hoods, bigger tool dust ports, larger diameter ducting, and sometimes even better tool designs.

    1. The size of blower to move at least 800 CFM at our larger machines depends upon the overhead. Overhead in a dust collection system is resistance measured as static pressure. When using minimal resistance filters and little to no ducting and no separator, it takes at least a 1.5 hp dust collector motor turning at least an 11.5" diameter impeller to move enough air. We need at least a 2 hp motor turning a 12" impeller if you add enough ducting for a two-car garage sized shop. Add the additional overhead of a cyclone with that ducting and we need a real 2.5 hp motor turning at least a 13" diameter impeller, but most find it better to have the additional capacity of a full 3 hp motor turning a 14" impeller. You can get by with smaller units only if you either use a bigger impeller, a more efficient impeller, or increase the motor speed well beyond the normal impeller 3450 rotations per minute speed.

    2. Almost all available inexpensive small shop dust collection ducting, fittings, and ports on our machines are too small. The standard 2.5" vacuum hose and 4" diameter small shop dust collection hose, duct, and fittings work well to collect chips, but are near worthless for collecting fine dust. If you had to change your garden hoses all over to 1/8th inch tubing, you would not be very happy with the result because that tiny pipe would all but kill the water flow. The same is true with airflow. The amount of air moved like water depends upon pressure and the pipe size. When moved at the up to 12" of pressure typical for small shop blowers, maximum air volume in a 3" diameter pipe is about 250 CFM, in a 4" pipe about 400 CFM and about 600 CFM in a 5" diameter pipe. It takes roughly a 5 hp motor turning a 16" diameter impeller to move the same amount of air through a 4" pipe that a 1.5 hp motor turning an 11" impeller can easily move through a 6" pipe. Picking pipe with the smoothest interior helps some, but not that much. With the pressures available from small shop blowers we need 6" diameter duct to move the 800 CFM that the air engineers have proven is the minimum to get good fine dust collection at our larger tools. Unfortunately this becomes an expensive nightmare as 6" pipe and fittings can cost ten times that of the competitive pricing for small shop ducting.

    3. The classic ducting design that works well for chip collection hardly works at all for small shop fine dust collection. Traditional dust collection system designs use down drops that are smaller than their main. These 3", 4", and 5" down drops make no difference in commercial systems because almost all of the ducts are open at once and there is plenty of airflow. This is not the case with small shop systems that normally only have one duct open at a time. A length of smaller duct will in about ten diameters reduce the volume to the maximum that sized pipe can support at the available pressure. This causes no problems in vertical runs because the airflow speeds up in that smaller pipe. However, when the air gets back to the main with only that single small pipe feeding the main, the airflow in the main slows badly. A main that supports an optimized 4000 feet per minute (FPM) duct speed will drop to 2100 FPM after about a 4' length of 4" duct. When the main air velocity drops below 3000 feet per minute (FPM) we build little dust piles in the mains that pose a serious fire hazard and can damage our equipment. These piles constrict the airflow until the air speed builds amply to get by. That keeps the pile from growing taller, but it just keeps growing longer and longer. Any spark from say cutting a nail or staple ends up with a potentially serious problem because the high airflow acts like a bellows fanning that spark into a potentially major problem. When you open a larger gate downstream then all the piles go slamming down the line. They get so large they will shoot through a separator and hit the impeller so hard they over time can ruin motor bearings, cause plastic and aluminum impellers to fail, and then ruin filters with holes, plugging, and reduced filter life.

  4. Fix Your Tools

    Economics have turned most small shop woodworking tools into copies of older professional woodworking tools that are now made in third world countries. Most of these older tools either had no dust collection or at best limited chip collection. To successfully collect fine dust from these tools they mostly require some modifications to control fine dust as it is made and permit moving enough air to capture that dust. You must also do your homework followed by making needed changes to your tools.

    1. We also mostly only have 4" dust collection connections known as ports on our tools. Convincing ourselves to voluntary tear up our expensive tools to replace the too small tool small dust ports with the bigger ports we need is not fun or easy to do.

    2. Likewise, we must also replace or change our tool hoods to control and allow capturing the fine dust at the source, or we are wasting our time and money.

  5. Good Solutions

    Hopefully at this point you are comfortable that we must upgrade our hoods and use all 6" ducting or we are not going to control the fine dust and move enough air to capture it. We also need a big enough blower to overcome the resistance of our filters and ducting. It takes a blower that will move a real 1100 CFM maximum to provide ample airflow with no ducting. It takes a blower able to generate a real 1200 CFM maximum to power the ducting for a small shop. For most small shop sized shops it takes a blower able to move a maximum of 1900 CFM or more to power the additional ducting. Providing less than this much blower will only end up in compromise solutions that do not move enough air to capture the fine dust at the source. Likewise, we either need to keep our dust collector outside and not return the air to our shop, or we need to provide at least 0.5-micron filters and preferably 0.3-micron filters for better protection. Here is my list of potential solutions for collecting the fine dust at the source and getting rid of it in order of effectiveness along with comments.

    1. I believe the best approach is to build an efficient cyclone and use ample 0.2 or 0.5-micron filters. This is the only solution that will not quickly plug our fine filters killing needed airflow and quickly wearing out the fine filters. Only my cyclone design and the no longer available WoodSucker cyclones meet these requirements. All other small shop cyclones use a combination of inefficient cyclone separation designs, too small of blowers, and too open filters.

    2. The next best approach is to use a 1900 CFM or better dust collector placed outside without returning any of the air inside. This presumes you have no gas, wood, or coal fired appliances in your shop that could fill it with deadly carbon monoxide and that you do not have a problem sending all your conditioned air outside.

    3. The next best approach is to use an existing dust collector replacing any old 30 micron bags with fine filter bags, build an airtight enclosure for your bag tree, and then come off of that enclosure with a fine cartridge filter. If you do not go with the finer bags that permit more airflow, this approach will kill your airflow. Don't forget to make your enclosure with a door that will let you beat the upper bag and empty the lower. For this to be effective in moving enough air to capture the fine dust you need a 1200 CFM rated dust collector that you move between machines with no ducting except a short length of 6" flex hose. To use this solution with ducting you need a 1900 CFM or larger dust collector. I find this solution better than just adding a fine filter because the dust collector bags keep most of the stuff out of the fine filters greatly extending their life and amount of airflow between cleanings.

  6. Lesser Solutions
    1. The next best approach is to convert your older dust collector to a cartridge filter. The problems with this approach is many early and less expensive dust collectors do not move enough air and they do not have a usable separation ring, so the filters will get plugged and ruined quickly. The best conversion is to follow my directions below with either a trashcan separator lid or Thien baffle to keep the larger chips from plugging the filter and punching holes in it. If you use a filter with a mesh inside then you also should use a fine screen to keep stuff from getting behind the mesh and ruining the filter. Replacing the original bags with a top quality cartridge filter from the various small shop vendors made for these conversions works, but most of the conversion cartridges offer poor fine filtering. With the worst health damage caused by 2.5-micron and smaller sized particles, these don't offer much protection. That's why I recommend using certified 0.5-micron or better yet 0.3-micron cartridge filters. With my support Wynn Environmental developed a new 0.5-micron wide pleated filter designed to mount right on most 1.5 hp to 2 hp dust collectors. They make this filter in the same paper poly blend that most other makers offer, and offer it in the far superior all poly version. Take a look at their solution by clicking here!

  7. Cartridge Filter Installation
    1. Now that these units have been out for a while, we have learned quite a bit about their strengths and weaknesses. Cartridge filters can provide better respiratory protection than bag type dust collectors, but each also shares some problems. Even with filters prepared with a dust "release agent" the increased airflow of these more open filters with far more surface area carries chips and dust into the filter leaving the pleats plugged. And, this increased airflow also causes some of the larger chips to hit the filter so hard they jam in place and can make holes that quickly ruin a filter. Cleaning the fine dust can be done with a vacuum or compressed air. CAUTION! When using compressed air to clean a cartridge do not go over 60 PSI or you will blow your filter apart! Unfortunately, neither compressed air or a vacuum do much good at getting the larger chips loose from the filters. These chips often require cleaning by hand.

    2. Although you can either buy a pricey cartridge filter kit to convert an existing dust collector, it is less expensive to do your own conversion. I initially shared a wide-pleated conversion. It works about the same as the commercial cartridge collectors suffering from the same clogging problems. To address that clogging I added a simple piece of window screen. It worked so well, I tried that screen with a finer filter. It worked even better. Now instead of recommending a wide pleated cartridge coated with a release agent, I now recommend use of a fine pleated cartridge filter protected with a screen. The Wynn and Farr compatible fine pleated filters I recommend provides real 0.5-micron filtering instead of the roughly 2-micron offered by the wider pleated filters. These have at least triple the area of the wide pleated filters that generally run under 100 square feet in area. This larger surface area greatly improves airflow, reduces filter resistance, and lets us go much longer between cleanings. We can also use the same filters that we use with our cyclones allowing us to later upgrade to a cyclone without having to buy new filters.

    3. Even these fine filters are not ideal as much of the finer dust will go up and stick to the filter. Still, unlike the wider pleated filters, the chips cannot hit the pleats and as soon as you turn the motor off and give the filter a tap or two, the majority of the dust will fall.

    4. There are many types of fine pleated filters used in dust collection. Sadly, most of the larger filter suppliers such as Wynn Environmental because they have good filters, like working with small shops and have good prices. They also carry good inexpensive 6" flex hose.

      I started using and recommended a pair of the Torit compatible cartridge filters (2A226BLFROL) that have about 224 square feet of filter area and come in a 12.75" diameter 26" tall unit. We can also buy these same sized cartridges in a more expensive washable polyester material. These come in 100 square foot units (#2A100SBOL), 140 square foot (28A140SBOL), and 202 square foot (29A202SBOL). Although pricey, these washable filters can be cleaned with compressed air like a paper/poly-blended cartridge. Then when that stops working, instead of having to replace the filter, they can be washed with a light soap and water giving it a total life of three to four times the less expensive units. These washable cartridges are what I recommended before discovering how to use the finer filters.

      Today, I prefer the Wynn and Farr filters. The Wynn information is on their conversion page mentioned above. The Farr is Part# 125154-005 compatible 300 square foot filter that is 99.4% efficiency at 0.5 microns when moving 1000 CFM. It is 12.75" in diameter by 34" long. I buy these as the Wynn compatible Farr filters (9E300BLFR). If you have the ceiling height, using two of these works better, but you should also get one with both ends open (9L300BL). Make sure you ask for the filter with the external metal grid, not the internal as I got as mine is much harder to clean! Talk to Wynn Environmental for the one best for you. In this case bigger is better! (Thanks Jack Diemer for introducing me to Wynn Environmental and Dick Bryan Polinski for pointing out the larger sizes!)

      Note that I also recommend the fire retardant filters and filters coated with a release agent. Make sure you have both before buying.

    5. We would get a little better performance by making a filter canister that sits on top of our dust collectors to hold the filter. A canister would push the air through the filter the way it was designed to work from the outside to the center and let us clean by vacuuming the filter outside. I don't bother because making a canister is much more work for little gain.

    6. Regardless of which you decide to go with, make sure you let Wynn know what you will be using it for so they don't send you a fine filter for the cyclone as that will not work!

    7. Required Parts: Torit style filter, threaded rod, matching threaded knob, fine metal screen, two nuts, two lock washers, and a small cross bar.
      or
      Farr style filter with wood doughnut, fine metal screen, and four bolts with t-nuts in the wood doughnut.

    8. Construction: The filters from Wynn Environmental, are near ideal as they are wide enough and have a seal that sits right on the donut shaped plate in the center of most dust collector bag trees without having to make a board or anything. To hold it in place, slip the rod through the sealed top hole and tighten up against the cross bar from the above picture. The cross bar needs to be as short as possible and still span the opening. Making it sit in the circling air stream will cause lots of turbulence and seriously degrade separation causing far more material to go up into your filter. Add your lower plastic bags and your modification is complete.

      Anyhow, at this point a few people had trouble with converting over their Delta 1.5 hp and Grizzly 1029 dust collectors. They work fine except when planning and joining. Joiners and planers create a heavy load of large sail like chips that end up jamming into the pleats causing a cleaning problem.

      It turns out that you can greatly improve the performance of these units with three fixes (thanks to Bryan Danner):

      1. If your dust collector does not have a separator ring, you need to add one. It should be tapered so the dust falls down into the bottom bag. The hole diameter should be 1/2 the diameter of your round bag tree assembly.

      2. Shorten the mounting bracket. Rather then simply crosscutting the board, miter cut it so that it's bottom edge extends into the air stream as little as possible.

      3. Mount a cleaning paddle to the threaded rod running down the center of the cartridge. It's 7 or so inches in diameter, extends the entire length of the filter, but does NOT touch the filter itself. It's made out of 1/4 inch plywood. If you get a plug, simply turn the threaded rod, and the paddle breaks the clog up and it drops into the lower bag.

      4. Install a neutral vane.

    9. Disclaimer

      The reader assumes all responsibility and liability associated with the hazards of woodworking and dust collection. Dust collection when improperly built, implemented, used, or maintained may cause serious injury or even death, so USE THIS INFORMATION AT YOUR OWN RISK! The author has no control over how a reader will act as a result of obtaining information from these pages. Your actions are your responsibility, VERIFY and CHECK information out before proceeding, and don't attempt anything without the required skills. The author shall not be responsible for any errors or omissions that may be present on these pages. Accordingly, the author shall assume no liability for any action or inaction of a reader.

      The drawings, procedures and words shared on these pages are as in use by the author and shared for information only. No claims are expressed or implied as to the safety, usefulness, or accuracy of this information. Neither the author nor any other references or links on these pages will accept any liability for any damages or injury caused to people or property from use of this information or from any associated links.

      These pages are directed toward a hobbyist and small shop woodworker audience and are not intended for application in a commercial, institutional, or industrial setting. Commercial woodshops are generally governed by a complex set of worker safety regulations, such as those mandated by OSHA. Satisfying the compliance of such regulations is beyond the scope of these web pages. HIRE A PROFESSIONAL ENGINEER to design, specify, test, and certify performance of any dust collection system if you have a commercial or an industrial application, allergies, other medical problems, people working for you, a large shop, work with hazardous materials, or are subject to regulatory oversight.

      Unless you as a woodworker provide appropriate fine dust protections, most small shop owners put your health, the health of those close to you, and even the health of your pets at risk. Unfortunately particle testing by the author and hundreds of others all across the country shows those who vent inside even with very clean looking shops invariably have huge build ups of invisible dust. Government testing shows on average just one hour inside a small shop that vents its dust collection inside results in more fine dust exposure than large facility commercial workers receive in months of full time work. The difference is almost all large commercial facilities vent their dust collection systems outside, so they rarely build up the fine invisible fugitive dust that escapes collection. Even with venting outside, the peer reviewed medical research shows the more fine dust we take in the greater the short and long term health damage and this research also shows even with their much lower exposures almost all large facility woodworkers develop serious dust triggered health problems and significant loss of respiratory capacity. This should terrify small shop and hobbyist woodworkers because of our much higher exposures. Respiratory doctors who have read these pages share small shop woodworkers and their family members often have the worst respiratory problems. Please take the time to protect yourself and those close to you.

Copyright 2000-2015, by William F. Pentz. All rights reserved.