Shop Works #2: Box Fan Dust Filter

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Blog entry by woodspar posted 07-25-2007 07:04 PM 45148 reads 11 times favorited 14 comments Add to Favorites Watch
« Part 1: Introduction Part 2 of Shop Works series no next part

Just built this quick project from an article in “Woodsmith” magazine. I made a few changes from the article.
filter fan
There were incorrect measurements in the exploded drawing in the magazine. For example, the top piece was labeled 21.5 inches, when it clearly needed to be 20.5 inches, like the bottom piece.
fan no filters
When I determined that some measurements where reported incorrectly, I gave up on reading the plan in the magazine and I started making some changes to the design. I based the size of the inner components of the wooden frame on the size of the filters.
left frame
I also decided to remove the inner fan grid and screw the fan housing to my wood housing. It makes it solid and keeps the fan from falling out.
right frame
You slide two 20×20x1 furnace filters in the slot in front of the fan.
right corner
I used a fiberglass filter in front of a pleated filter. The pleated filter is not rated as high as I would have liked; there was a filter that claimed micron level filtering. It significantly more expensive than the pleated one I got. I wanted to see how the box fan motor handled the pleated filter to begin with before I spent more on the micron level one.
peek a boo
So far it seems to work pretty well. It is very portable, and the wooden frame makes the fan very strong. The frame also makes the fan extremely stable.

-- John

14 comments so far

View Bill's profile


2579 posts in 5326 days

#1 posted 07-25-2007 07:15 PM

Great work John. Any dust collector is better than none. Have you noticed a difference since you started using this in your shop? Less dust lying around I bet.

-- Bill, Turlock California,

View woodspar's profile


710 posts in 5264 days

#2 posted 07-25-2007 07:26 PM

Thanks Bill. Yes, I guess the main thing that I see is the filter is getting covered up with dust.

Right now I am using it on my porch. I am scraping paint. Once I forgot to turn the fan on and I thought – this is kind of dusty – then I realized that I had not turned the fan on! So, I guess it makes some difference.

-- John

View TheGravedigger's profile


963 posts in 5189 days

#3 posted 07-25-2007 08:24 PM

I was thinking about making a couple of these just this morning—talk about coincidences! I take it that it’s really effective?

-- Robert - Visit my woodworking blog:

View woodspar's profile


710 posts in 5264 days

#4 posted 07-25-2007 08:37 PM

I think it will be most effective in the case of the first picture where it is right next to the work piece on the workbench.

The design in the magazine called for two of the fiberglass filters. The pleated filter taxes the fan a bit. You perceive a reduction in motor speed.

In my environment (garage shop) I wanted a way to move dust away from my work area. At first I was using a small portable desk fan. This design allows me to keep dust out of the fan and trap some of the dust at the same time.

One needs to consider the ability for the chosen filters to capture particulate. These furnace filters are really not designed for the micron stuff. The micron filters require more power to pull the air through. I will buy a “micron” filter and report back on how the fan handles it.

Of course this is no substitute for adequate dust collection and the use of a breathing mask.

-- John

View Douglas Bordner's profile

Douglas Bordner

4074 posts in 5229 days

#5 posted 07-26-2007 04:37 AM


On the second series of shots, it appears the fan is resting on some MDF with a lot of holes. Is a downdraft table or a series of dog holes?

-- "Bordnerizing" perfectly good lumber for over two decades.

View woodspar's profile


710 posts in 5264 days

#6 posted 07-26-2007 04:49 AM

The mdf with the holes is a Festool MFT
indeed the holes are dog holes of a sort…
(ask mr spid-ato man about dat MFT.)

-- John

View oscorner's profile


4563 posts in 5476 days

#7 posted 07-26-2007 04:54 AM

Nice work.

-- Jesus is Lord!

View woodspar's profile


710 posts in 5264 days

#8 posted 07-26-2007 04:57 AM

Thanks Os!

-- John

View Karson's profile


35276 posts in 5565 days

#9 posted 07-26-2007 05:39 AM

Great Idea. What did you use for the fan. I picked up a couple of fans at Walmart and it seems that move very little air. A real reduction from previous versions. That really made the air move.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Appomattox Virginia [email protected]

View woodspar's profile


710 posts in 5264 days

#10 posted 07-27-2007 06:41 AM

Yes, Karson, I think that you may be right, these inexpensive fans are just not that powerful. It does help move the dust away from the work area, though.

-- John

View Chuck Anstrom's profile

Chuck Anstrom

92 posts in 4189 days

#11 posted 06-16-2010 08:22 PM

Did this unit continue to to assist in dust clean-up? Do commercial dust filtration units have any significant advantage?

-- Chuck Anstrom - Virginia

View woodspar's profile


710 posts in 5264 days

#12 posted 02-11-2011 12:42 AM

Helps with dust, not a total dust control solution. Recommended for garage Lumberjocks only.

-- John

View sluggo's profile


14 posts in 3743 days

#13 posted 05-08-2011 06:00 PM

Hi woodspar,
I just recently joined Lumberjocks and saw your Box Fan Dust Filter which I thought was well designed. My question is which issue of Woodsmith did this plan appear and also might you know of a PDF of this design thats out there? I ‘m just getting started in woodworking.
Any help would be appreciated.
Thanks Bob

-- Sluggo,Illinois

View TheUnkownChemist's profile


7 posts in 3269 days

#14 posted 08-21-2012 09:15 PM

I was thinking of running the exhaust thru my dyson to get the small stuff.
Stacking 2 fans would increase the flow rate for about $20.

-- Mark D. Saler. Some of Life's little lessons are lethal. Learn from others.

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