Shop Built Air Filter

  • Advertise with us
Project by OldKranky posted 960 days ago 7563 views 94 times favorited 37 comments Add to Favorites Watch

I scored a free 4 speed furnace blower the other day and decided to build a much needed Shop Air Filter system. I found some plans at
All it cost me was $30 for the 3/4 Birch plywood and a few hours of my time.

Note: Thanks to LJ Rance for showing me his disposable Kerfmaker that I used to make the slots for the sliding cover plate. It worked like a charm on the first try.

You may notice the filler boards for the filters. I built it for 16×25 filters but had scored a dozen 14×25s form the local Re-Store for $1 each a few days ago.

Thanks for looking at it …...

-- Better looking at it than for it....

37 comments so far

View SwayzeeJon's profile


14 posts in 986 days

#1 posted 960 days ago

Looks great! Let us know if it works as well as you hope it will.

-- "Have you ever heard the phrase, 'Give a boy a video game and he'll play all day - teach a boy a video game and he'll play for life?' Me neither - take him fishin!" - Bill Dance

View LesB's profile


1063 posts in 2079 days

#2 posted 960 days ago

Old furnace squirrel cage blowers work great. You did a nice job.
I put mine into a larger cabinet with wheels so I can roll it around to different locations when needed.
Mostly I have it blowing across my wood stove so it also circulates heat in the shop. You know how cold and damp the Northwest can get in the winter (-:
I use a double layer of filters, a coarse outer filter and a finer inner filter.
The top of the cabinet is used for my sharpening center where my grinder and slow speed wet sharpener are mounted. Extra space in the cabinet under the blower section is used for storage. The blower has lasted 15 years but I have a spare if it ever goes out.

-- Les B, Oregon

View Gabe C.'s profile

Gabe C.

288 posts in 977 days

#3 posted 960 days ago

I’m adding this to my favorites. I need this for my garage shop!

-- If I could just get this whole "Time/Money" problem figured out...

View Dusty56's profile


11644 posts in 2324 days

#4 posted 960 days ago

Very nice looking project : )
I wish I had thought of doing this before spending so much money on the store bought one.

-- I'm absolutely positive that I couldn't be more uncertain!

View HorizontalMike's profile


6928 posts in 1550 days

#5 posted 960 days ago

Major envy here! The furnace blowers are hard to come by cheap.

-- HorizontalMike -- "Woodpeckers understand..."

View NormG's profile


4114 posts in 1640 days

#6 posted 960 days ago

What, sounds like an excuse to do wood working. Nice job, will put on my list

-- Norman

View a1Jim's profile


112027 posts in 2213 days

#7 posted 960 days ago

A great shop filter job.

-- Custom furniture

View ortega5629's profile


7 posts in 967 days

#8 posted 960 days ago

I’m so bummed i just replaced my furnace with a full functioning blower. I wish i had the foresight to have kept it. Well done!

View tinnman65's profile


1124 posts in 2050 days

#9 posted 960 days ago

I have one of those blowers that I saved from a furnace years ago. Thanks for posting this ,I really should get this made for my shop. I really like the retro fit filters, I just picked up some at Lowes that had been opened for 50 cents and they just happened to fit my furnace but they had several sizes for the same price. Nice work!

-- Paul--- Creativity is allowing yourself to make mistakes. Art is knowing which ones to keep. — Scott Adams

View Greg..the Cajun  Box Sculptor's profile

Greg..the Cajun Box Sculptor

5030 posts in 1945 days

#10 posted 960 days ago

You did a really nice build for your filter. What made you decide to use 3 filters for the intake side? I have several I built for my shop and I use just one filter…but wonder if more intake filters would be better if it wouldn’t restrict aid flow.

-- If retiring is having the time to be able to do what you enjoy then I have always been retired.

View grumpy749's profile


216 posts in 1013 days

#11 posted 960 days ago

I used a single filter on each side of my version but i like your stack idea. I have to blow my filters out with compresed air at least once a week. I used hepa one micron filters and I love the way it cleans.

-- Denis in Grande Prairie. Yesterday is history, tomorrow is a mistery, but today is a gift. That is why it is called the present.....Pink !

View Grandpa's profile


3107 posts in 1312 days

#12 posted 960 days ago

Greg the “store bought” air filters have a pre-filter an then a better filter that is rated for .5 micron. I think the best thing would be to bite the bullet and get the $50 .5 micron filter for the home made systems. It would really clean the air. The pre-filter would remove a lot of the nasty stuff before the inside filter removed the really fine dust.
Kranky, your system is nicely done. good job

View OldKranky's profile


121 posts in 968 days

#13 posted 960 days ago

Thanks everyone for your comments.

I have two filters on the intake and one on the exhaust side. I built it as the plan showed.

-- Better looking at it than for it....

View Bearpaw's profile


208 posts in 2357 days

#14 posted 960 days ago

I built the this about 10 years ago and it has worked great. You will enjoy it. I have mine mounted to the ceiling directly over my table saw. It helps in moving the air to heat up the shop.

-- "When we build, let us think we build forever." John Ruskin

View Eddie's profile


27 posts in 967 days

#15 posted 960 days ago

Thanks OLDKRANKY i just moved into my new shop working on a router table now but the air system will be next thanks for the post and the kerfmaking jig i need it for the table now fan box looks good and Bearpaw had one for 10 years so im going with it. as soon as i get a good camera ill post my new shop

-- Jesus is ok with me

showing 1 through 15 of 37 comments

Have your say...

You must be signed in to post the comments.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

Latest Projects | Latest Blog Entries | Latest Forum Topics :: gardening showcase