# 2-Blower dust collection system with shop made fittings: the good and the so-so



## Sark (May 31, 2017)

A few years ago, I bought two 2-HP Grizzly dust collectors for $300 and determined to hook them together to make a cost-effective high-performance 4-HP system with 6" metal ducting feeding into and out of a 6" super-deputy cyclone separator.

Encouraged by some posters on this site, I also decided to make my own duct fittings. To go into detail would require a very long blog, and I don't have the time for that. But I'd thought I'd share some photos and thoughts about the process.

First some photos of the current system…which now reaches 4 major pieces of equipment: table saw, band saw, chop saw, and 6×48" sander.

Note: my garage has a shed roof that is high at one end. This allows a u-shaped storage-mezzanine where the blowers are mounted. They exhaust directly outside since we live in a semi-rural area.










The ducting in and out of the cyclone separator was hard to figure out, and it was one reason that I decided to make my own fittings. Prior to starting I mocked up the system with 1/8" plywood to get an idea of where the ducts needed to run. Actually making the fittings (wyes, butt joints, angled butt joints, reducers) turned out not to be that hard--once I figured out how to do it. Putting it all together (blast gates from Blastgates, inc) was a lot of work. The separator seems extremely efficient, and I've not noted any dust on the trees by the exhaust vents.










Bought 5' lengths of 28 gauge 6" ducting through Home Depot mail order. Rather like the shiny sturdy look of the metal. It seems quite strong and was lowest cost metal ducting of that thickness I could find. Shipped in from Canada. Made a shroud for the chop saw, hooked up my old Unisaw through the front access panel, and connected the sander and bandsaw through the provided ducts.










How does it work?

Super suction power, but only 'pretty good' dust collection. Why the so-so rating? Effective dust collection depends on the quality of the hoods, shrouds and quality of the machinery's design for dust collection as much as it does on the size of the blowers. My chop saw's shop-built hood is pretty good, gets the fine dust but a lot of the coarser dust is left behind. The Unisaw has essentially no dust collection ports, and does not have an overarm blade dust collector. The Laguna bandsaw is pretty good, but could stand improvement. The Jet sander has a port but really poorly designed ducting.

That being said, the dust collector system is vastly superior to no dust collection. It is very quiet, only 70db at the table saw. The TS and dust collector together produce about 72db. For comparison purposes, the air compressor is 80db and the DeWalt planer is an ear splitting 99db.

Custom duct work:

If you're interesting I can do a separate post on how I made the fittings. Rather than using the typical adjustable elbows I just made the duct unions to fit. One union was 30 degrees and another 8 degrees. It gives a very clean look to the installation. Tools required were an angle grinder (for cutting the profiles), sheet metal snips and a spot welder.


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## kelvancra (May 4, 2010)

On your explanation of the so-so collection at some equipment, yep to that.

(1) My 6×48 drum-disk sander:

(a) It needs better collection at the top of the belt, where it just peeks over the edge and its way back around.

(b) In the vertical, angled or horizontal position, it needs a flap at the very bottom, connected to the housing for the belt and dragging on the lower cabinet top, to better contain the air draw from the collector.

I used a piece of flexible vinyl duct tapped at the bottom.

(c) A table that might be said to be more of a zero clearance table helps, but, like on my edge sander, it needs shallow notches to allow the draw of the collector to pull from above the table.

(2) While either of my miters have dust collection ports, they seem to be little more than second thoughts.

It MIGHT be a regular vacuum would work better than my collector, BUT I went with one of the flexible nylon hoods connected to a dedicated HF unit (it does double duty as a pine cone vac off a cyclone) via a 4" port. That was a game changer. However, the area well above the miter is significant, so the hood could be lowered, or I could run another piece of nylon, to better focus the air draw around the cut. That concept works beautifully on the sanding station, next mentioned.

I did swap the stock fins for the Rikon one and, immediately, noted at difference at the miter, but MIGHT have, for some reason, lost a bit in the pine cone collection business.

(3) The sanding station. One of my favorite places to work in the shop: I get to sit down, while I work; I sand there, occasionally use the router there; and I use the Foredom, the Ram and the dental drill for carving there.

Because my station, unlike the sad things even Rockler sells, has sides, a top and a back, the collector's 4" hose can only pull air in from where I am working. Using a 1/2" carbide bit, you can watch the dust roll off a piece of wood and take a curved path into the collector. So to it goes with all but the big chips off a router run.

(4) The lathe is a challenge. I never have to worry about sanding dust with a small hood made from 8" plastic pipe. 99% of everything off small spindles and bowls gets pulled in too [along with the occasional project  ]. Everything else needs a second draw from the front, lower section, or a flex hood just right or left of the work area.

I have a feeling swapping from my 3 horse beasts (two four baggers) to yours might be an interesting test.


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## Sark (May 31, 2017)

On the Jet 6×48" sander, note that the internal ducting is 2" but terminated in a 4" port. With the undersized ducting, it requires needs a lot more static pressure than my 4HP system can develop. Perhaps the shop vac would be superior here.

I considered getting a 5 HP system, but given that the 'bottleneck' is more likely the hood/shroud, I think it would be a waste of money. Now upgrading to Oneida's supercell might be really worth while, but I'm already committed to 6" ducting, and don't want to spend the money…


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## kelvancra (May 4, 2010)

Since mine is a Powermatic, I assume it has the same, poorly figured internal ports.

I have an extra reducer on hand in case the one on the oscillating sander takes another hit [from me]. I should connect up a shop vac just to see how it performs.

Since my collector is next to it and the band saws just back and 90 to it, I, often, pull a hose off the small saw and hold it in place via the base of a seminar display stand. With it, the internal port and the other mods I mentioned, the dust problem is greatly reduced.


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## clagwell (Dec 20, 2018)

Looking at your ducting I think you would be better off to cascade the two blowers instead of using them in parallel. That would double your static pressure.


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## Cajunrotor (Jan 11, 2012)

You also mentioned your use of the front door on your old Unisaw for dust collection. I, for one, would be interested in how you configured that. I have a 1946 model Unisaw and even with an overarm vac port (Sharkguard) the collection needs improvement. I don't want to cut into the original sheet metal to attach anything, but the door port might be useful. Maybe between the two I'd have something.


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## ibewjon (Oct 2, 2010)

The 28 guage duct is awful thin for your setup. Be careful to be sure a port is open when turning it on. I would have used 24 guage to be safe.


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## wapakfred (Jul 29, 2011)

I would be curious to see measurements of the air flow with one blower running, and then again with both blowers. Not a request, just an observation.


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## clagwell (Dec 20, 2018)

> ...cascade the two blowers instead of using them in parallel. That would double your static pressure.
> 
> - clagwell





> The 28 guage duct is awful thin for your setup…
> 
> - ibewjon


Hah! I missed that. Maybe he doesn't want more pressure.


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## Sark (May 31, 2017)

Yes, you get more pressure with a series connection of blowers than with parallel…but of course, less cfm. I suspect that the static pressure of my system is adequate, but that hood design is lacking or non-existent (as in the case of an overarm dust shroud for the table saw). So improving the hood design would come before increasing static pressure.

A 5 HP motor with a bigger rotor would probably provide both an increase in cfm and static pressure, and can be had for $1,000 roughly. Some of the guru's of dust collector systems can weigh in on this subject. Fact is that two motors hooked together does not double the performance, either in static pressure or in airflow. Intrinsic loss of efficiency. One bigger blower is better than 2 smaller ones…but for $300 that I spent, it's hard to beat the performance.

The 28 gauge metal ducting seems quite up to the task…I'd be surprised if the overall static pressure couldn't be doubled before noticing anything resembling collapse. Would that happen with 2 blowers in series? I doubt it. The ducting is all 6" diameter, and the 2 HP motors are a bit under 5" diameter. So a series connection would slow down the air speed, which is bad, but not sure if it would make a difference.

Here's how I hooked up to the table saw. No internal baffles. But it works pretty good (my standard) at removing the dust which is pulled down into the cabinet. Before I fuss with internal baffles, I would get an overarm saw blade dust shroud.


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