Got any pictures? Its hard to follow you verbal description.
How did you determine how much CFM you were getting? I don't know of any way to measure it.
How big is the motor on your collector? There's hardly any difference in capacity among collectors if the blower is properly designed and sized to the motor capacity.
Bob
I didn't follow you exactly, but roughly speaking, you added two bags to the system to give better air flow. Is that about it?
Being married to a "real" Yankee, who is Scottish to boot, has had a marked influence on me. I am now offically "frugal," though most would call it cheap.
With that intro.
Several months ago I bought a 1600CFM dust collector from Harbor Freight. I knew the 1600CFM was "optimistic." When it arrived what I had was a dust collector with two very porous (30+ micron) bags, one to collect and one for the "filter." So in effect there were two very porous filter bags. I replaced the collection bag with a black plastic bag and the filter with a "shaker felt" bag from Highland Hardware. Filtration increaded dramatically, CFM dropped even more dramatically. I now had about a 600CFM dust collector - at $149.95, still not a bad deal.
However, I decided to upgrade the system a bit. Lo and behold! CFM is now up to about 1200.
Here is the upgrade, (total cost about $60.00)
I ordered to collector rings (Part #33) for my dust collector (model #
45378) at $14.35 a piece for a total of about $32.00 when s/h is added. I ordered another "shaker felt" filter bag from Highland Hardware for $29.95, about $34.00 with s/h.I then built a box 21w X 42L X 5H box, divided it on the top into two squares with a 5" cross piece, then put 2 1/2 wide peices around the inside of each opening and triangular corner blocks to give me two octagonal openings about 16"w. On the botton of the box i located a similar opening in the center of the bottom. Then put two pieces of 1/4 luan between the bottom frame and the upper ends to give me a slope for the dust to slide down into the collection bag.
Then I mounted the box to the collector on the dust collector with angle braces and caulked the joint. I took the two new collectors, cut most of the inlet off of one and cut slots in the other inlet, then slid one inside the other and screwed them together with sheet metal screws. I then mounted the two collectors over the top holes, secured with angle braces and caulked. Then attached the bags in their respective places and turned it on. Worked like a champ. Total cost for a moveable 1200CFM dust collector, about $220.00 (dust collector, collectors, bag)
Deb
On Thu 01 Jan 2004 09:48:30p, "Dr. Deb" wrote in news: snipped-for-privacy@corp.supernews.com:
I bought that same DC just before Christmas.
Curious: How are you measuring your CFM?
Two of those metal rings that separate the two cloth bags. Okay...
A plywood box, 21 inches by 42 inches, by 5 inches high? Or is that five feet?
Lemme see here...
Boy, I wish I had pictures of this. You mounted the box on the original collector ring. To the top or the bottom of the ring?
Damn this communications barrier!
I can't understand. I can't get a picture in my mind of what's happening. I see two collector rings, one inside the other, stuck on top of the original collector ring, a box underneath that, and two bags, um, someplace. Or maybe one of the two collector rings isn't completely inside the other one. Isn't the dust just roaring out all those extra holes?
Deb, can you draw a picture and send it to me or something? Can anybody explain what it is I'm not grasping? My mind's locked up. Why is this thing so much better now?
Dan
Hey Dan, it was perfectly clear - in the mind of the writer. For the rest of us, we're groping. I get very frustrated when someone tries to explain something more complicated than a breadbox in words. It just doesn't work.
Bob
On Thu 01 Jan 2004 10:53:23p, "Bob Davis" wrote in news:7P6Jb.15736$ snipped-for-privacy@newsread2.news.pas.earthlink.net:
Yeah, and I can't blame Deb for it. This is where words just plain fail. I've been on the other end of this problem more times than I want to remember. But I'm gonna get this one, dadblast it! :-)
Dan
Like the others, I need a picture. Could you take one and post it at ABPW (alt.binaries.pictures.woodworking)?
I think what you did was turned your single bag collector into a dual bag collector by making a plywood manifold. Two new shaker bags on top to filter and either one or two black plastic bags hanging below to collect the goodies. Am I close?
Total cost for a moveable 1200CFM dust
your still not doing 1200 cfm. unless you have huge bags and I mean big. but even then without bags I doubt you can do 1200. will with no pipe maybe (G)
First thing that popped into my mind was that for about $30-40 more one could just buy the Grizzly collector (G1029Z - pg 120 of the new catalog) which is now being shipped with a .3 micron bag and does 1550 cfm already. Nothing to build or swap out just hook it up and it sucks!!
Jim
Well, actually it's a bit more with the $55 shipping, but I'm stuck with
120 volts and 60 amps max for a while. I have to take the next model down and make the best of it. If there's a chance I can get better efficiency by adding another bag, whether it's really pulling 1200 CFM or not, I'm happy to listen. :-)And I believe Bill at
What I've also been considering is leaving the DC just the way it is, putting it in a corner and enclosing it in a bunch of good furnace filters on a 2x2 frame. The shop's pretty small, wouldn't need a lot of duct and hose to get it to every machine. Think that's worth an experiment?
Dan
I will make an attempt at a drawing and parts list on post to the al.tbinaries.pictures.woodworking site sometime later today.
Deb
Dr. Deb wrote:
You're right about the shipping, I never considered that I guess because Im close enough to just go pick it up. Im as curious as you and the rest are however about how Dr. Deb is measuring CFM's. If Bill is right about the 50% rating then Dr. Debs actually started out as an 800, went through the mods and then ended up as a 600 right? ....................................Easy, I'm just jokin with ya!!
Jim
experiment?
Be careful when claiming "X" number of CFM in your dust-collection system.
The CFM figures provided by most vendors who do not deal in industrial systems sold to large commercial companies (those companies have engineers who can spot phony specifications a mile away) use CFM like Detroit uses "horsepower" in automobile engines. There is no industry-standard set of conditions under which CFM is measured for consumer goods, which means the company can invent any scheme they want to get the highest CFM reading they can. As long as they can prove that the machine moves that many CFM under conditions they created, they aren't open for fraudulent representation.
Caveat emptor: "Let the buyer beware".
The only way to measure CFM and static pressure accurately is by using a pitot tube inside the duct with a manometer or Magnahelic (R) gauge setup. The numbers published by sellers of consumer-oriented dust collectors have little connection to how the system will perform in a real shop environment.
If you want to really understand dust collection, and how CFM relates to having a safe shop, visit Bill Pentz's dust-collection web site at
I manufacture kits for the cyclone and blower housing, based on his design. That info is on the same site at
Clarke
On Fri 02 Jan 2004 11:07:09p, "James D Kountz" wrote in news:16sJb.33003$ snipped-for-privacy@news01.roc.ny:
I envy that. :-)
I figure it started at about 800, dropped when it got the new bag, and increased when it got the second one. I like the 45 CFM/sqr ft constant, it seems plausible for getting a ball park figure. Maybe a little more when new, a little less when caked, but at least it's a place to start. I also believe Steve Knight when he says it's probably not even close to 1200, but even if you got it back up around 800 with felt bags... oh, you were joking. Never mind. :-)
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