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Dust Collection Mastery

When you look at someone else’s shop, you can’t help but to think of improvements they could make.  But what would you say about your own shop?

Jet Dust Collector - Single Stage with Singed Felt Filter Bags

Here’s my upgraded Jet DC-1100 dust collector. I bought a large 16 oz. singed-felt filter bag, and a non-breathable, sealed duck-canvas lower bag to ensure fine dust collection. Notice the difference between the picture below and this one. No coating of fine dust. The reason you see the coating of fine dust with the original Jet bags is because the lower bag is a breathable, woven polyester bag. It let particles 30-micron and below right through. This fine dust is difficult for your lungs to handle; your body can’t filter the finest wood dust lower than 10 microns. This singed-felt filter bag filters down to 1-micron 96-98% brand new (without a dust cake), and even more after a dust cake develops. BIA Classification rating “G”.

After a cleaning session,  my shop generally stays clean for a week or so.  After cleaning, the next day I go in there happy about the new organization.  But I noticed something.  Dust all over the floor again.

Normal, right?

I looked around and realized that not every tool was hooked up to dust collection.  The main ducts had the taps already in place, I just hadn’t hooked them up yet.  One offender is the oscillating spindle sander.  Another is the mortiserSince it wasn’t already hooked up, I used the tools anyway and just put up with the chips and dust.  Now I have extra clean-up to do.

Lesson learned?  If it’s not convenient, you won’t bother.  That’s the secret to an awesome shop.  Set things up to be as automated as possible. If it’s not, it becomes a deterrent to making shop time for yourself.

So take yourself out of processes that you don’t need to do, and your workflow will be much smoother.  Things like turning on and off the dust collector, your music in the shop, and marking/ measuring tools should all be at your fingertips.  It takes some planning (but not a whole lot) to hook up all of your tools to dust collection, but the payback is continuous in not having to connect tools before you use them.

Dust Collector Jet

My main dust collector for the filter bag upgrade, with 6” diameter duct riser, which splits into two 5” diameter main ducts. Off of that I tap the 4” diameter duct branches to each tool. Plenty of suction, machines stay clean with this on. Note the 6” flex hose so I can move it around a bit to clean around it. With better filters from American Filter Fabric Co., I no longer have this fine dust layer you see on the black flex hose and frame.

Here you can see the duct drop to the floor sweep, and the branch on the right side is the 25 ft. of 2-1/2” flex hose I use for general shop vacuuming. Super useful.

Dust Collection Options

A friend asks you to help him with his shop ideas.

“What kind of dust collection system should I consider?”

“Ahh, I’d put in a central collector, duct it to each machine, and have a remote on/off keychain with me.  Put blastgates at each machine to maximize suction on the tool you’re using.  Then you can do woodworking without dragging a shop vacuum or small collector around the shop or re-hooking up flex hoses. “

Now, if you’d recommend this to someone you care about, what about you?

There are many ways to do this, but there are better ways.

You could have, in order of “annoying” to “awesome”:

  1. A regular shop vacuum that you hook up to one machine at a time.
  2. A regular shop vacuum that you pre-duct to several machines and use blastgates
  3. A Festool shop vacuum that you do either of the above
  4. A small 650 cfm collector that you move from machine to machine
  5. A medium-sized central collector, single-stage, maybe 1100 cfm, that you pre-duct to all your machines
  6. A central, high-powered 3-5 Hp cyclone collector (or single-stage with professional-grade filter bags) that you pre-duct to all your machines with 16 oz. singed-felt filter bags or HEPA cartridge filters

Installing the ductwork only took a few days. By first drawing a plan, then picking up all the materials, I put it all together assembly-line style.

What surprised me is that to set up the current system I have, a Jet DC-1100 central collector with sheet metal ducts and a keychain remote, didn’t cost that much.  A few hundred for the collector and a few hundred more for all the duct and fittings.  The installation was not too bad either.  I just needed straight snap-lock ducts, elbows, wye fittings, a few 5” to 4” and 4” to 2-1/2” transitions, metal strapping to support the ducts, UL 181-grade foil tape, duct sealant and some self-tapping screws.

Works great, but could be improved for better fine-dust collection, as I describe in my filter bag article.  If you wanted to install something higher-end, such as a 3 hp cyclone with cartridge filters, 6″ ducts, thicker gauge ductwork, etc. I don’t think it would break the bank if you did it incrementally.

WoodChip Tip:  Put a series of magnets on your floorsweep’s screen that will instantly attract screws and other metal debris to prevent you fan from getting damaged.  Rare earth magnets are really powerful and will work even better.  They’re cheap too!

This floorsweep allows me to use a broom and sweep large piles of sawdust to this location to send it to oblivion. I added a metal mesh screen here to prevent larger objects from hitting the impeller of the collector.

Pro’s and Con’s of Different Systems

Using a shop vacuum may technically work, but the 2-1/2” connections aren’t that big so you don’t get the proper air quantity (cubic feet per minute) that is recommended for table saws and planers (usually around 300-500 cfm) for the most basic chip collection. Also, shop vacuums are loud due to their universal motors, and fill up quickly unless you have a small $100 cyclone chip separator such as the Dust Deputy.

Having a single stage or two-stage/ cyclone collector is really the proper way to do it, in my opinion. An upgrade that I’m considering is using a cyclone type central collector with 1-micron filtration, or a more powerful single-stage 3-5 hp model with a much larger 16 oz. singed-felt filter bag. I’m currently using 5” mains for my 3-car garage (20’x30’) shop (works really well), and I branch 4” ducts to each machine; but if I upgrade to a higher-CFM dust collector I would probably look at 6″ mains.

NOTE:  For branch ducts, you need to realize that if you’re closing all of your blastgates except one, you’re taking the FULL dust collector airflow from that branch duct.  So, 4″ may not be enough (it will cause too much static pressure loss, resulting in lower CFM).  Plus, from large tools like your jointer and table saw, in order to catch all of the dust you need more than the typical recommended 450 cfm.  I notice that my jointer can get clogged at the inlet sometimes, so I may enlarge this connection, and to do a proper job at my table saw I plan to collect from BOTH the back cabinet and blade guard.

If I take air from two locations in one tool, the airflow needed will go up, and for my table saw probably around 800 cfm at minimum.

I do have some 2-1/2” taps for smaller tools like the drill press which should probably be 4″ diameter.  Remember how much air (cubic feet per minute,CFM) you get at the tool will depend on your dust collector’s static pressure capability, filter surface area/ airflow resistance, duct size, and how many elbows and other duct air restrictions are present.

Here’s a collection of accessories, including a swivel connection, hose clamps, duct hangers, foil tape (makes a perfect seal), and a roll of metal strapping.

A central type collector is more of a set-it-and-forget-it system. I position it in the corner out of the workflow, but centered between the two main ducts. I duct two main branches in each direction. This is to keep any one main line to any tool shorter, reducing the static pressure (resistance to airflow) to each machine. This is because you calculate static pressure based on the longest run from the collector to the most distant machine connection. So one long main trunkline is actually not as good as two shorter mains with the collector in the middle, provided you collect dust from one machine at a time.  In industrial shops, you’re collecting from everything at once but those dust collectors are huge to handle that much air.

To me the biggest factor is convenience (assuming dust collection is adequate). I don’t like to do certain things in the shop. They’re tedious and boring, and aren’t creative. Re-connecting flex hoses for every cut breaks up your workflow, takes energy, and eventually you may tend to make quick cuts without turning on the collector. Then your shop gets all covered in dust and is unpleasant to work in, and your lungs receive cumulative damage.

Each machine has its own connection configuration. Here at the router table I collect dust and chips from both underneath the router and from the cutterhead itself.

This is what I do:

I walk in the shop after a snack or after watching Rough Cut, reach for the keychain remote and clip it on my belt loop, then grab a stack of boards that need jointing. Then I open the jointer’s blastgate (sometimes closing the one that’s open first), hit the “ON” button on the remote, and start jointing. When I’m done I hit “OFF”.

Next up I get ready to head to the planer. Before doing that I close the blastgate on the jointer, then go to the planer and open that blastgate. Then I hit “ON” again, rinse and repeat.

The only thing wrong with this picture is that I have to manually open and close the blastgate at each machine (I could leave a few open at one time but I like to maximize suction at the one I’m using since I don’t have a million horsepower cyclone). Ecogate makes a product that will automate this. That to me is the ultimate in shop dust collection. It totally sounds worth it. How much is your time worth in $/hour? If you waste 10 hours in a month on switching duct connections and running over to the collector to turn it on and off many times a day, you could’ve bought yourself a cool system and saved all that physical energy.

WoodChip Tip: Make sure you leave enough slack in the flex hoses; you want to be able to rotate your machines to make infeed/ outfeed room, or to clear a temporary open are to stage a project.  But don’t use too much since flex hose has a much higher resistance to airflow than smooth duct.  This lowers the airflow you get at the tool by quite a lot; I’ve measured this with an anemometer.

 

Dust Collection Duct Drop Around Obstacles

 

Important Accessories You Don’t Want to Forget

In future blog posts, I’ll dive into more detail about things like accessories, air cleaners, and detailed design (like how to calculate your duct sizes) but here’s an overview of things that you shouldn’t forget about when sitting down to design your dust collection.  For more info, go to the Dust Collection Resource Page as well.

  • You’ll need to support your ductwork. I use sheet metal strapping, about 3/4” to 1” wide. It comes in rolls that you can cut to length with tin snips.
  • Blastgates (I like to use foil tape and duct sealant to prevent leakage thru the side-seams while they’re closed; get good aluminum ones!)
  • Use metal hose clamps to secure flex to the blastgates.  Use the “bridge” type that crosses the ridges on the flex duct to get the best seal.  They make 5″ diameter as well.
  • For the seams in the straight duct, elbows, and blastgates, you’ll need to brush on duct sealant.
  • For the connections you may want to take apart later, you can use foil tape (UL-181 type).
  • Copper wire to ground your flex duct to prevent static electricity build-up (I got a surprisingly strong shock from my planer’s non-metal flex a few months ago)
  • Swivel or ball-joints to use on machines you’ll be moving around a lot to lessen the stress on the sheet metal ducts from the motion of the flex hose
  • Floor Sweep with a metal mesh grate (and maybe rare-earth magnets to help catch screws)
  • Provide a 2-1/2” tap from your floor sweep duct drop and coil up about 25 ft. of flex hose to use as a general shop vac cleaner. I have my shop vac on the opposite side of the shop, so this works on the side it can’t reach to clean the floor and walls.  Be careful here; put a mesh screen on the suction point so you don’t injest stuff you don’t want hitting the impeller.  Rare earth magnets would help this too, and having a cyclone also helps.
  • Chip separators use a cyclone action to collect the largest particles and chips, and only the smaller dust particles make it to your collector bag. This makes emptying easier and less frequent. The bin at the cyclone separator is even easier to empty than the dust collector’s lower bag.  Just be aware that separators like cyclones and trash can lid types can have up to a 4″ pressure drop.  Therefore, you’ll want a pretty powerful dust collector, certainly more than 1.5 or 2 hp.
  • Flex duct-supporting wall hooks can help support sagging flex hose and keep bends to a minimum
  • Of course, don’t forget the remote control!
Sketch Your Design!

I’ll pause here so you can go do your sketch. Doo doo doo…hmm hmm hmm… Ok.

To start, just use your workshop layout and make a few copies of it. Then locate your dust collector, and think about your main lines. I used 5” diameter duct because it has less pressure drop than 4” for the CFM my collector has, and also it’s not oversized to maintain enough air velocity to carry the chips back to the fan (make sure you maintain around 4,000 – 4,500 fpm velocity).

Then draw the branch ducts to each machine. Now really think here. Make sure the flex hose that drops down won’t interfere with stock feeding into or out of the tool. I neglected this at my table saw and so I had to fix it.

If you use more than one machine at once, but not all at once, your design gets almost infinitely complicated.  You don’t want your collector to be sized for one or two machines’ airflow in the main ducts and then have several open blastgates.  This is because if the airflow drops too low in your main ducts, dust will accumulate thus increasing your fire risk (slow air velocity won’t carry the particles/ chips effectively).

You want to maintain a good air velocity in your ducts at all times.  My system is designed to handle one machine at a time, which makes it easy to predict and calculate, and I get sufficient velocity in my main line at the longest run.  The California Mechanical Code, Chapter 5, Table 5-1 calls for a minimum duct velocity of 3,500 feet per minute for “Average dusts, such as sawdust, grinding dust, coal dust”, but dust collection companies and other articles I’ve read recommend around 4,000 to 4,500 feet per minute to do a good job carrying chips in real life.

Vertical risers are probably more critical because they’re prone to accumulation at the bottom.  If you have an elbow at the bottom of a riser, consider installing a cleanout at this location by installing a wye fitting instead, and putting a cap at the bottom.

 

Dust Collection Anemometer Airflow Meter

The only way you’ll know if you’re getting close to the recommended CFM is to measure it. If you think you have enough airflow because all the chips are being picked up, you might be missing the finer dust that you can’t see. That’s where knowing if you have the CFM recommended by industrial hygienists and organizations like ACGIH comes into play.

Calculate Your CFM and Velocities

Now, you can calculate your duct velocity by taking your duct CFM divided by your duct’s cross-sectional area, but often you don’t know the actual CFM you’re getting.  It’s dependent on your duct system’s static pressure losses.  There are duct static pressure calculators online, but it’s sometimes difficult to figure out what all of the device pressure losses are (blast gates, filters, fittings, flex duct, etc.).  I bought an airflow meter a few days ago so I will know if I’m getting the recommended CFM and velocity values from each tool.  Some of the good manufacturers have fan curve data, showing you the predicted CFM at a given static pressure.

For example if you know you have 8″ of static pressure from your planer back to the dust collector, the fan curve might tell you that it’ll only do 400 CFM.  If this isn’t enough air, then you’ve got to reduce the static pressure in your system.  Larger radius elbows (more gentle curve), larger diameter ductwork, enlarging the collection port at the tool, and reducting duct length are all things you can do to accomplish that.  Check that your ducts aren’t too large; that’s a bad thing because velocity DECREASES with duct size increases.

There are a few machines on which I’d like to increase airflow, namely my jointer and drum sander.  I think the 4″ branches aren’t sufficient, so I’ll be increasing these ducts (and connecting ports) to see what CFM I get.  Plus, if I use one machine at a time, and if you want to maximize your airflow, it only makes sense to have the same duct diameter branch as the main if you think about it.

If I upgrade my collector to a cyclone or high-powered single-stage unit, I’ll probably do a thorough static pressure calculation (I’ve done quite a few as an engineer) to size the ductwork.  My guess is that I’ll end up with a 6″ main, and 6″ branches to the table saw, jointer, drum sander and planer to get the airflow I actually want based on some quick rule-of-thumb calcs.  Remember, if you’re collecting from one machine at a time, check your longest run static pressure and consult your manufacturer’s fan curve (CFM vs. Static Pressure) to see what the predicted airflow is.  Also look at your largest CFM-requiring tool and check that the static losses from the machine back to the collector results in enough CFM and air velocity.

One of my drawings for my dust collection system showing the overall layout.

When you’re done with your planning, note the lengths of each duct so you can buy it. Then make a list of how many of each size elbows you need, wye fittings, duct size transitions, how many blastgates, etc. Then go to your local woodworking store and buy as much of these as you can. These stores don’t usually sell sheet metal straight duct so you can go to your “big box” home store for that. I found that I had to order my long-radius elbows online (which have a lower pressure drop than standard elbows), and the same with some of the wye fittings.  I currently use 30 ga. duct, and it’s been fine.  If you have a powerful cylone, and you close all of your blastgates accidentally, 30 ga. may collapse unless you have a barometric relief damper.  Check with the manufacturer on design requirements; you’ll get a lot of tips that are specific to what you’re building.

But that was it, I bought those things, didn’t spend as much $ as I feared, and now I have a pretty good system that I can keep upgrading!

CHECKLIST:  Procedure for Designing Your System
  • Choose a Dust Collector Type
    • Small dust extractor (such as Festool’s) or shop vacuum
    • Small single-stage collector
    • Medium-sized single-stage
    • Larger single-stage or cyclone
  • Choose a Filter Type
    • Cartridge pleated filter, preferrably MERV-15 or higher (such as HEPA)
    • 16 oz. singed-felt filter bag with plenty of surface area
  • Choose a Duct System
    • Localized flex duct (not too much!)
    • PVC networked to each machine
    • Sheet metal networked to each machine
  • Draw the layout of your system, at least to start
    • Choose overhead ductwork, or ductwork running low along your walls
    • Avoid too much horizontal ductwork on the floor in the middle of your shop, particularly traffic paths
  • Size the ducts
    • If you’re using one machine at a time your mains and branch ducts should be the same size
    • Maintain between 4,000 and 4,500 feet per minute velocity (Velocity = CFM divided by Duct Area)
    • Get the fan curve from the manufacturer of the dust collector you’d like to buy, or maybe someone online has tested and mapped one
    • Calculate the static pressure of the duct layout you’ve drawn (there are online calculators that can give you an estimate)
    • Only count the ductwork of your longest run, and then check the run from the collector to your hungriest machine as well, all using the CFM requirement of that machine
  • Size the collector
    • To give you the CFM you need at your hungriest machine with the static pressure of that duct run, check the fan curve
    • Check the fan curve for the longest run static pressure you’ve estimated, and make sure the collector can give you the CFM of that machine
    • If you’re ambitious, you can check each machine’s run, one at a time.
  • Write down the accessories you need/ want
    • See Accessories list above
  • Create a parts list
    • Linear feet of straight duct
    • Number of elbows, 90 deg. and 45 deg.
    • Number of wye-fittings
    • Linear feet of flex hose
    • Number of each accessory noted above
  • Look at your tool hoods (remember dust collection is most effective at the source)
    • Consider upgrading from 4″ to 5″ or 6″ as long as the CFM allows for enough velocity
    • The Jointer in my shop tends to clog with shavings at 4″
    • Look at dust collection at your table saw overarm guard like this one or this, or make one
    • Make tool hoods at things like your miter saw, router table, drill press, stationary sanders, lathe

Here’s my Dust Collection Design that I did in AutoCad, a free PDF download for your reference to help you design your shop!

I used long-radius elbows to decrease static pressure losses in my system. These elbows have a radius 1-1/2 times the duct diameter. Standard elbows have radii 1X the duct diameter Also there is less chance of clogs by doing this.

 

Related Articles:
Does Your Dust Collector Filter Bags Spray Fine Dust Up Your Nose?
My New Dust Collection Filter Bags Arrived!
Dust Collection System Layout ‘Strategeries’
Dust Collection Ductwork and Fittings Done Right
Dust Collection Resource Page

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15 Responses to “Dust Collection Mastery”

  1. Joel Danowitz says:

    Hi,

    I am working on my dust collection at the moment, I hate the calculations for sure. And that brings me to my question. I have the same dust collector as you. I added a wynn environmental filter and an Oneada Dust Deputy. I am running 6″ PVC for my main and would like to be able to calculate everything. However, I dont have the fan curve. Would you happen to have this?

    Thanks
    Joel

    • Bobby says:

      Hi Joel,

      I’ve just sent you an email with the fan curve files that I’ve got. I haven’t asked Jet directly (not sure whether they would want to send it but maybe they’d help). I use an anemometer to get my duct velocities, and you can use a manometer to get the pressures and test/ generate your own curve with your particular setup. In other words, your dust deputy and Wynn filter add a certain amount of static pressure to your system (dependent on the CFM though) so that may be the most accurate way of doing it. Assuming you’d only run one machine at a time, then you can make your branch ducts 6″ as well as long as your velocities would be maintained at the minimums I mention in the article. Before gluing the joints together (if you plan to do that), test the velocities at the inlet of each machine and make sure you have enough velocity to carry the dust while the other blastgates are closed. If not then an increase in filter surface area would help, as would sealing system “leaks”, or decreasing the length of the flex duct.

      Cheers!

      Bobby

  2. Carl says:

    This is very helpful, thank you. My questions are even more basic though, and I’ve not yet found a vendor or hobbyist website that addresses them, so maybe I’m just very confused. I plan to put a dust collector within 15 feet of my table saw (which has a 4″ outlet built in); my router and planer will be within 10 feet. I don’t intend duct work. Instead, I’m thinking of running a 6″ diameter flex hose out of the collector, right up to connect to a tapered reducer (to 4″) into the machine.

    So my questions are: does this approach suggest that I need a very high powered dust collector? I was thinking something like a Jet DC1100-CK which is 1.5 HP. But could that handle the 15′ of flex hose and deliver enough capability at the saw?

    Next question: Would it help if I run a short (say 3 foot) duct from the saw -> reducer up from 4″ to 6″ -> 3 feet of 6″ pipe -> gentle 45 degree turn -> then some kind of connection to the flex hose? (The pipe would run under my outfeed table.) I’d probably still need the 15′ of flex pipe (or cut it down to 12′?) so I’m not sure if this would help or hurt (since I’d be adding a sweep)?

    Last question: since I will move the hose from machine to machine manually, what’s the best way to connect to the (reducers attaching to the) built in outlets on the equipment? In other words, the best way to connect reducer to table saw, and then best way to connect flex pipe to that reducer (assume I go 6″ flex pipe so each device has its own reducer and I just move my flex pipe from reducer to reducer)?

    Thanks for any ideas on this from folks. I’m thinking a dust collector would be more fun than wearing a dust mask but I’m pretty intimidated by this stuff.

  3. Paul says:

    Thanks for the start. I am currently in construction phase of a 2 car garage with connecting workshop, 16’x24′. All brand new and needing of planning. My tools are in the basement and I have a medium sized dust collector. Plan to print out your article and draw to my dust collection plans.

  4. Gary says:

    Look at the Clearview cyclones, 5. Hp and a hepa filter. My shop has never been so clean and boy do they move the air

  5. Karl says:

    I just recently moved and am in the process of setting up my woodshop in my basement. I have a Jet DC650C (canister based) dust collector that I’ve attached a large trash can based “chip collector” to that I’ve been using in a connect to tool as you go sort of way. Tool wise, I have a table saw, miter, 6″ joiner, 12″ planer, misc. routers and sanders, with hopes of adding others. I know the DC650 is probably undersized for running some permanent duct work with only 4″ ports and 1hp, but I’m not sure I can squeeze money out of the budget just yet for upgrading it. Do you have any suggestions on what I can do to reduce the connect as you go using this collector? FYI, I’m getting great information from your blog and look forward to applying the principles you have in setting up my shop here.

    Karl

    • Bobby says:

      Karl,

      Thanks! I went from no dust collector to a shop vac to a Jet DC-1100 which I still have. The DC650 is better than nothing of course; it will pick up chips and coarse dust. If you have very small amounts of flex duct connecting directly to the tool you might be getting decent airflow, much better than a shop vac.

      The more CFM you get the greater distance you can collect the fine dust; the suction distance drops radically with distance, meaning you need much more CFM the further away you want to draw in dust. For example, alot of organizations such as the ACGIH recommend 400 CFM for table saws, but the reality is you want more than that, at least 800-1000 to be able to grab the fine dust cloud around you. Drum sanders especially. Of course a good blade guard w/ a dust hose is really effective at the table saw, and good hoods at other tools are critical.

      Make sure you seal all the connections on the DC-650; I’ve read in some reviews that they’re not sealed completely.

      Now if I had the DC-650, I might look at centralizing the collector and radially distributing ductwork to each tool, though that compromises your layout. Permanent ductwork with this gets tricky, because too much (flex plus sheet metal with elbows and fittings = static pressure that reduces CFM significantly). You can also look at getting quick-connect fittings (Rockler has them) to reduce the time it takes to switch from machine to machine.

      Or, depending on your basement shop’s layout, you could located the CFM-hungry machines together and use the collector to duct locally to those, and use a shop vac for portable sanders, routers, etc. In fact, I have my T-Saw, Planer, and Jointer in a “work cluster” anyway for ergonmic workflow, so that would be good for reducing ductwork as well.

      I had a 1-car garage shop with one wall lined with tools, and a duct running along the floor/ wall that branched to the table saw and router table for only 15 ft. of duct or so, and short branches of only +/- 18″. This helped reduce the static pressure and at least maximized the CFM I was getting.

  6. Jeremy,

    The chip separator does cause a pressure drop, decreasing the CFM you get out of the collector, so I tend not to use it since I just empty the bottom bag on my collector. I use a singed-felt upper bag filter, so I’m not worried about excessive dust build-up on it. It’s designed to allow the excess “dust cake” fall off, and the proper amount, which helps filtration, stay put. Your collector has a higher CFM/ static pressure capability than mine, so you might be ok with the extra pressure drop. Use 1.5 or 2.0 R/D elbows, minimize flex hose (enough just to move the machine around how you need to), and think about using 5″ ductwork rather than 4″.

    With your collector in the attic, a chip separator may add convenience for emptying, if located at ground level or maybe on a reachable shelf in. In that case, if the major chip-producing machines are hooked up to the separator, that may be ok, as the main collector bag would fill up less often.

    I have my mains split into 2 runs, so if you do the same, one main can pick up the heavy-chip machines, and the other main can pick up the rest. When calculating static pressure losses, it’s done by using one run, meaning from one machine all the way back to the collector. So, by splitting the mains, it’s easier to have any one complete run shorter which lessens your pressure drop.

    -Bobby

  7. Jeremy Sanders says:

    Bobby,

    Thank you for the great article and education. I am in the process of organizing my very small shop (a 1-car sized shed with an attic space above it). I am planning on locating my dust collector in the attic space above my shop and having the main line run through the attic. A couple questions though: I am planning a DIY chip separator, should that be connected directly to my dust collector and then all the tools get routed through the chip separator, or should I only send the major chip producing machines (jointer, planer, router) through the chip separator? I just picked up a Grizzly 1550cfm machine with 2 inputs.

    Regards,
    Jeremy

  8. Jamie Sifton says:

    Bobby – signed up but didn’t get your email to confirm. Please re-send – this is the right email address (make sure it’s ‘brothers’ not brother ‘dressler.com

    • Bobby says:

      Jamie,

      Let me know if you still didn’t get the email; sometimes it will land in a spam folder. It shows that it went through, though but I can do it manually.

      Bobby

  9. JR says:

    Good article and full of ideas. I would add a few things. You seem to be partical to Jet. They used to have the right price for performance, but I think Grizzly has really overtaken them. You can get a 1550 CFM (6″) 2.5 micron for $315. The nearest Jet would be $200 or more over that. Performance is good as is the durability and maintenance.

    I just redoing a shop and really have questions on drawing every line up, instead of across the wall at the level of the collector. I know commercial/industrial operations do that all the time but those draw far more air and have easy access panels (not duct tape removal points. You seem to be running just fine with those up-draft points, I guess.

    What are you using for a duct source? I find this stuff way over priced and the HVAC guys will rip you off if you try to buy through them and Home Depot always seem to have only a few of the parts needed. Any tricks to make sure you’ve got enough gates open so you don’t collapse your duct work?

    I think a good cabinet saw really needs 1000 CFM to keep it ‘clean’. Sander tables also seem to chew up the CFM’s as well. Is there any really good source for CFM requirements on ‘dust generators”

    Thanks,
    JR

    • Bobby says:

      Thanks, JR! Yeah, I like Jet only because that’s what I’ve had for a decade now with no problems and good performance, and I keep seeing good performance ratings for them on static pressure and CFM (impellers and motors are good). I’ve been hearing that Grizzly is packing more for the $, but back then I was afraid of the quality issues they were having.

      For your duct runs, you certainly can run the ducts low along the wall, no problem. I did that in my one-car garage shop in Ladera Ranch. In my current 3-car garage, I ran them overhead because I have a lot of machines in the middle of the floor. Smaller shops tend to have machines along the walls to leave you room to move around and stage projects in the floorspace. The goal is to reduce the number of elbows (and flex hose) you need. Static pressure (airflow resistance) calculations for systems that use one machine at a time are based on the duct run from the collector directly to that machine; the branches to “off” machines aren’t counted except for a small tap-off loss along the way. So, machines like sanders want to have more direct duct runs so you get the max CFM given your collector’s capability.

      I’ve seen some shops design “in-floor” duct work, but structurally you have to make sure the floor is strong enough for heavy machinery and materials. You could do this in a shop you design from scratch. But, I think this limits the adaptability in your shop layout.

      For my ductwork, I did go to Lowes for the straight duct, but for the elbows I had to go online to Penn State Industries or Oneida to get the long-radius elbows. The home centers only carry the short-radius elbows, which is a much sharper turn. This causes more static pressure in your system than a 1.5 or 2.0 R/D elbow.

      As far as ducts collapsing, with my system I use straight duct around 30 ga and don’t have any problems with only one blastgate open. And I sealed the heck out of each seam and joint on every elbow and wye fitting with duct sealant plus foil tape. If you have like a 3 hp cyclone, you may want to have larger ducts anyway (like 6″ diam.) so if you have one blastgate open the static pressure in your system isn’t too great. Bigger filters help here too. I saw on one guy’s website a spring-loaded pressure relief damper where a hinged door would open inward as the duct pressure increased; it was held back by an adjustable-tension spring. He tested and tested it until he set it just right. By testing I mean having an anemometer and manometer so you don’t compromise on CFM too much on any one machine by decreasing your system’s static pressure. I’d only use a device like that if you have machines really close to a powerful collector with 4″ or less diam. and there’s a good chance that might be the only open blastgate. 26 ga. duct or less would probably eliminate that issue but of course it’s more $.

      I’ve seen CFM charts online if you Google CFM Requirements Woodworking or something like that. ACGIH publishes one; that’s the book I used for my calculations. Some people like Bill Pentz argue for more CFM to capture small particles, and as an engineer I know he’s generally correct. ACGIH even has a calculation method that tells you how far out you can collect fine dust from a suction source. It’s not very far unless you have a lot of CFM. I tested this myself with my Jointer flex hose; I took my anemometer and pulled it away until it read 50 feet per minute and then took a handful of fine dust powder, stirred it up, and watched it be drawn in the hose. As I got around 12″ away, it stopped pulling the dust cloud in. This hose does around 550 CFM or so. I typically am more than 12″ away from the machine so that means the fine dust near my face wouldn’t be picked up. Therefore I know I need more CFM. An ambient air cleaner and more cross-flow ventilation in the shop would probably help too.

      You can always add your own “safety factor” if you think you need more air based on experience. The more air you have the better fine dust grabbing ability you’ll have. My table saw (a SawStop) does pretty good with around 600-700 CFM I’m measuring currently. I plan to improve this by increasing from a 4″ diameter connection to a 5″ or 6″ plus a hose to a custom blade guard, but based on my current collector with the enhanced filters (see my article “Does your Dust Collector Filter Bag Spray Fine Dust Up Your Nose?”) I’m getting much better airflow to the point where a 4″ duct is too restrictive, and I’d get good velocities with 5″ for sure. This will increase the CFM since the static pressure will then be lower.

      Bobby

  10. Peter Ford says:

    Just downloaded your guide to setting up a wood workshop. First glance looks very useful and looking forward to working through it slowly.

    My wife persuaded me to get a saw dust collection unit for my workshop which gives me a great opportunity to re-organise the entire workshop and contents around the new dust collector unit.

    Thanks for giving me something to start the project with – just in time!

    Peter.

    • Bobby says:

      Awesome! The outline is what I came up with and used (though handwritten at the time), and I just filled it out under each heading until I had a list of detailed requirements. Undoubtedly you’ll find conflicts, like maybe too many tools vs. space to walk around. For example, I decided to skip a second table saw because there just wasn’t room.

      I hope you find your workshop building project just as fun as making stuff! Let me know if there’s anything I can do to help.

      Bobby

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