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?
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.
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 mortiser. Since 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 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”:
- A regular shop vacuum that you hook up to one machine at a time.
- A regular shop vacuum that you pre-duct to several machines and use blastgates
- A Festool shop vacuum that you do either of the above
- A small 650 cfm collector that you move from machine to machine
- A medium-sized central collector, single-stage, maybe 1100 cfm, that you pre-duct to all your machines
- 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
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!
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.
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.
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.
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.
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.
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!
Gotta get more clamps,