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Making a cyclone chip separator for a dust collector

Picture of Making a cyclone chip separator for a dust collector

A dust collector should be one of the first major purchases for any woodworking shop.  Not only do they help keep things clean and tidy, they also protect your lungs from harmful airborne dust.  A dust collector is only as good as it's filter, and as filters fill up with dust it reduces airflow and efficiency.  One way to reduce this is to create a chip separating baffle, which collects most of the debris in a trash can before it reaches the filter.  This instructable will show how I created a chip separator for my dust collector.
 

 
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Step 1: The dust collector

Picture of The dust collector

Being on a tight budget, I chose the 2hp model from Harbor Freight.  I waited until it was on sale, and then used a 20% off coupon making the total price around $165 with tax.  I think the 2hp rating is a little overly generous, but it still can't be beat for the money.  The filter that comes with it only filters down to 5 microns, which means it won't collect the dust that is most harmful to your lungs.  Rather than spend a bunch of money on an aftermarket filter, I decided to vent my system outside, eliminating the filter completely.  I highly reccomend this approach if you're able to.

Step 2: The recepticle

Picture of The recepticle
I buy used plastic drums for use as trash cans and storage containers in my shop.  They are easily found for little or no money, lightweight, durable, and come in a variety of sizes.  I chose a large 60 gal size so that I wouldn't need to empty it as often.  I also used a white one, as they are semi-transparent, and I can see how full it is without having to remove the baffle and look inside.  Most of these drums have a solid top with two 2" bungs, so you'll have to cut the top off with a jigsaw or reciprocating saw.  You might get lucky and find one of the removeable top varieties.  It's generally a good idea to make sure the drum didn't contain anything toxic before you start cutting into it.  The ones I buy are were all previously used for transporting and storing food goods, but I still give them a good rinse before doing anything with them.

Step 3: Taking apart the dust collector

Picture of Taking apart the dust collector

When I first bought the dust collector, I assembled it in the standard configuration so that I could test it, and compare the results to my finished product.  I then of course had to take it all apart.  The only pieces we'll need are the motor and fan assembly, the center ring, the hose, and the fittings.  You can skip this step if you're buying a new un-assembled unit.  Most of the excess parts went into the scrap pile, but the casters were actually pretty nice quality, so I think they will go under a new rolling tool cart I plan to make in the near future.  The center ring has 6 holes in it where the supports bolt on.  I simply used the bolts to plug these holes. 

Step 4: The baffle concept

Picture of The baffle concept
The baffle is modeled after the design Phil Thien came up with to increase the efficiency of his shop vac.  This design has been used and modified by many people with great results, so I figured it would be a good place to start.  He has a great website showing his final design, along with other great information-  www.cgallery.com/jpthien/cy.htm

 His design puts the baffle under the lid, and it fits down into the recepticle.  This would be a little tricky for my plastic barrel trash can, as the sides are convex.  I thought that the center ring of the dust collector would make a great housing for the baffle, especially since it already has a lateral inlet.  It also has a cone inside that is intended to keep chips down in the bag with the stock set-up, which should only help with keeping the cyclonic action going.  The other advantage this has is that it allows me to use the full capacity of my trash barrel.

My idea was to create a disc that would fit on top of the trash barrel, and that the center ring would then fit on top of.  There would be a channel cut out of the disc near the perimeter of the barrel 2/3 of the way around, emmulating the Phil Thien design.  A second disc would then be fitted on top of the center ring, and the blower could then be mounted on top.

Step 5: Making the bottom disc

Picture of Making the bottom disc
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After looking around my shop for a suitable material, I found some scraps of 1/2" MDF.  I thought it might be a little thin and flimsy, but I had enough to make two pieces that I could later laminate together to form a 1" thick piece.  I used my router circle cutting jig to cut two pieces a little larger than than the trash barrel.  I then used a round nose router bit to route a groove in the bottom piece that would accept the top of the barrel.  The barrels aren't perfectly round, so I sorted through the 5 I had, and chose the one that was roundest.  I then routed another groove in the top piece to accept the bottom of the center ring.  With both pieces milled to shape and size, I then glued and nailed them together, making sure not to nail near the area where the channel will be cut.

With the grooves cut, and everything test fit sastisfactorily, I then marked out the channel.  The Thien design uses a 1 1/8" wide slot that runs 2/3 of the way around, but it is designed for use with a shop vac, and a smaller diameter trash can.  I wasn't sure how the lower static lift and higher airflow of a dust collector would effect the design.  I had a suspicion that mine would need to be larger, but I decided to use 1 1/8" to start with, so that I could enlarge it slightly later if I felt it needed it.  I drilled 1 1/8" holes at each end of the channel, and then used a jigsaw to cut the rest out.  I could have use my circle cutting jig again to make a perfect arc, but I would have had to make several passes to cut the full 1" depth, and the jigsaw just seemed quicker and easier at the time.  Since I want the chips and dust to fall into the barrel, but not come back out, I used some sandpaper by hand to slightly round over the top edges of the channel.

Step 6: Making the top disc

Picture of Making the top disc
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For the top disc, I found some scraps of 5/8" OSB.  Once again I decided to laminate two pieces together for added thickness and strength.  Just like the bottom disc, I used a roundnose router bit to form a groove that would fit on top of the center ring.  The scraps I had were just barely large enough to cover the ring, and as you can see in the pic, it barely had room for the groove.  I then measured the inlet of the fan housing, and cut a hole in the center that would fit snugly.  I noticed that the square outlet on the fan housing was preventing it from seating fully, so I notched the top of the disc.  I tested it to make sure it was a nice flush fit, and then used some construction glue to attatch the upper disc to the fan housing, creating an airtight seal.

Step 7: Creating the gaskets

Picture of Creating the gaskets
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Being that the barrel and center ring aren't perfectly round, and it needs to be close to an airtight seal, I wanted to form some sort of gasket where everything fit together.  I decided to lay a bead of silicone caulk in each of the three grooves I had routed, and then used my finger to smooth them into a convex shape that would help contour to the mating parts.  This creates a flexible and airtight seal.  The silicone takes 24 hours to fully cure.

Step 8: Assembly

Picture of Assembly
After letting the silicone cure, I put everything together.  One of the reasons I didn't attatch the center ring to the base disc is that I want to get the alignment right first.  I placed the bottom disc on the barrel, and then placed the center ring on top of the disc.  I put the inlet of the ring in place above the solid portion, emmulating the Thien design.  I just guessed at proper placement, and then made temporary reference marks on the outside of the center ring and disc.  This way I have a starting point, and can adjust the alignment in either direction to get maximum perfomance.  Once I get it tuned up, I can make permanent reference marks or even attatch it permanently so that it's perfectly aligned every time.

Then I mounted the top disc with the fan and motor assembly.  I used the short length of flexible hose that came with the dust collector as a vent.  I wasn't comfortable installing it permanently just yet, so I just ran the vent hose out the nearby window for now.  I plan on using a dryer vent for the final permanent installation.

Step 9: Flipping the switch

Picture of Flipping the switch
Because the motor is now on it's side, the on/off switch is now upside down and on the back side of the unit.  I simply removed the switch box, and rotated it 180 degrees, so that it's now right side up and facing the right direction.  The only modification required was to drill a new hole in the mounting plate for the wires that run from the switch into the motor.

Step 10: Testing it out

Picture of Testing it out
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I hooked up a length of hose and ran a few tests with some of the machines in my shop.  I ran a few boards through the planer, the jointer, and the tablesaw.  The airflow and collection seem to be as good if not better than the stock set-up.  I then had a helper stick the hose straight into a large pile to sawdust while I watched the exhaust outside.  There was a visible amount of fine dust coming out, but it was surprisingly small.  All of the chips, and the vast majority of dust were collected in the barrel.

After a minor adjustment to the inlet alignment, and enlarging the slot to 1 1/4", I was able to improve the performance even more.  During most normal operations there is so little dust being exhausted that it can't be seen with the naked eye.  Sucking up a large pile of dust, or taking heavy passes with the jointer or router table will create enough fines that the exhaust is visible, but just barely.  So far I've filled the barrel just over 3/4 full, and there doesn't seem to be any scrubbing or loss of airflow so far.

I currently have most of my equipment on wheels, and they are all set up at the same height in order to use the same outfeed table behind my tablesaw for everything. This makes it practical to install the dust collector near the outfeed table, and just use one 10' flex hose for everything.  I may install permanent ducts sometime in the future if I ever expand my shop, but this set-up seems to work well for now.  The only machine the hose doesn't reach is my bandsaw, but it doesn't create much dust, and I think the higher static lift of my shop vac works better for my bandsaws dust hood set-up.

I made a few modifications to my contractor style tablesaw in order to get more efficient dust collection with the new set-up.  I used a piece of hardboard with magnets to form an enclosure for the back of the saw.  I also used some magnetic sheet material (old car magnets) to reduce the gaps between the frame and the table top, as well as the slot on the front of the saw.  These can all be easily moved for making bevel cuts.  The last modification was to drill a hole in the ZCI just behind the blade to help reduce above the table dust.  This has reduced above table dust by about half.

very good idea first off! am building one now. ?. did u finally use 4" or five inch hoses for inlet an venting? also, how long was vent to outside?

thanks, mike l.

has any thought of putting a flame under the exhaust to use the dust to heat the shop during the winter months. it would help to cut down the environmental dust down alot?
vtxmanmike2 years ago
Are you still running this setup? I have an old Grizzly single stage DC that looks just like yours. I think mine is a 1.5hp, 240 volt unit rated at 1150cfm. Mine blows a lot of dust out of the top filter bag. If I convert, I'll still be exhausting into the room, so I'll have to adapt some filter bag anyway. I built a simple cyclone in front of the DC. It does a nice job of catching the bigger stuff but the bag on the DC still fills with shavings.

Please comment as I'm ready to make a change to my DC now!
Thanks, Michael
mcheung3 years ago
Did you find a need to add any pipe extension to the blower inlet so it sticks down closer to the baffle top?
mcheung3 years ago
Really glad to find this write up. I've just bought the HF DC, and was planning a much more complex build with a large cone. My workshop is on the 4th floor of an industrial loft building right up against the freeway, so I'll be venting outside as well. Good to know the simpler Thien baffle will separate enough that chips are not making it through to the other side.
tlott4 years ago
I just built a version of this, but decided to do the chip separator without the ring on it ( I needed the ring to put a bag on because I don't have the option of venting outside.) Anyhow, I spent a couple of days on this and found, to my frustration that the airflow was EXTREMELY reduced by the addition of a barrel, so much so that the bag on the collector would not even inflate, and I'm using the same model Harbor Freight Collector. A couple of days and about 30 bucks in materials later, I would caution persons against this project.... unless you are prepared to lose about 1/3 to 1/2 of your collectors power.
bigfreeinfo4 years ago
I was just about to start building a lid for a 20 gallon trash can with a Thien
baffle. I like you design better, and I hate to just throw the center ring away and not use it. I'm going to vent to the outside through a dryer vent as well. I was wondering what the final "adjustment" to the inlet vs the slot was. Can you post a drawing of the exact position of the slot in conjunction with the inlet hose on the ring. Or email it to me?
kidharris5 years ago
I thought about doing something similar, but decided against it. My worries were.....
That the blower was not designed to be operated in a vertical position. The shaft bearings may wear out quickly since they were not meant to support the load of the shaft pulling downward against the face of the bearing. I tried to find out about the bearings in mine but the manufacturer wouldn't answer my query.

Also the blower may possibly come loose and cause some damage or tear the housing apart since it also was not designed to be pointing downward. Gravity may help pull it loose or tear it all apart. Mine is only held on to the shaft by a setscrew, which is fine in the horizontal position. I'm not sure but I think that most vertically mounted blowers utilize a bolt and oversize washer threaded into the end of the shaft to hold it on.

I was also worried that the sheetmetal housing might not be strong enough to hold the weight of the motor without bowing in a little and changing the clearance between the blower and the front of the housing.

If yours is the same as mine (and it looks it), I would put it as far away from where I was working as I could. At the very least if it came apart right next to me, it would scare the devil out of me. There is a lot of kinetic energy going on there when it is at full speed and I'm not sure how much resistance a lightweight plastic barrel and a piece of plywood would offer in the way of containing it if it starts coming apart. If it starts sounding funny I would shut it off immediately. The Chinese products are not widely known for for being quality products and I didn't want to push my luck.

So....Is it still holding up now, 6 months later?
tashiandmo (author)  kidharris5 years ago
It's holding up fine.  I had similar concerns at first, but after asking around at some of the woodworking forums, I saw that many many people had turned this and other models horizontal and still had no issues years later.  It would have been easy to leave the motor and impeller upright and use a short hose or elbow, but I decided that I liked fewer turns in the airflow and a more compact set-up.  Laying the motor and impeller horizontally is probably the most common set-up when adding a baffle or cyclone to a DC.  Even many of the commercially available cyclones have this orientation.

The impeller housing is more than strong enough to support the motor, and even if it bowed slightly, there is a disturbing amount of clearance beteen the blades and the housing.  I almost wish it would bow a little so that efficiency would improve a little.

Since writing this 'ible, I've run PVC ducting to most of my tools, and made a bunch of blast gates.  I've also rigged the assembly to lift off the barrel with a ratcheting hand winch and some pulleys, which makes emptying the barrel much easier.  I also permanently secured the exhaust to something similar to a dryer vent.
I use the same collector.  It works great but the pictured switch doesn't last long.  When mine melted, I replaced it with a heavy duty light switch.  I find it much easier to turn on and off now.
furley5 years ago
What is the reasoning behind cutting just the channel for dust and not cutting out the whole center?
tashiandmo (author)  furley5 years ago
It helps create something similar to a vortex, so that the dust and chips get trapped in the container.  If you just left it open, most of the dust and chips would blow right through and out the exhaust.  It also prevents scrubbing, which is when the dust in the container is sucked out as the container gets full.
socrateez5 years ago
If your design was a little different, you would have a true cyclonic filter. Many can be seen atop grain elevators. Many are capable of filtering below the size you indicated.  Dyson Vacuums are designed around the same science.

www.billpentz.com/images/ClearVuelogo3.jpg This link is a pic of anothers attempt at just such a filter for your purpose.
Still, Kudos on the re-purposing design and "MacGyverism"
tashiandmo (author)  socrateez5 years ago
Yeah, I've seen the Bill Pentz plans for a sheet metal cyclone, but as I'm venting outside into the desert, I didn't feel it neccesary to spend that kind of time and money.  I should mention that his cyclone design combined with a good filter (ie. wynn) is by far the best option if you aren't able to vent outside.  He has excellent and comprehensive instructions for building one on his website.
I lived in Phoenix so know how dusty the natural desert environment is. I agree, venting outside in the desert isnt really contributing very much to the dust levels in the air. Nice job.