Art Posted December 25, 2017 Report Share Posted December 25, 2017 I'm thinking about building an air filter for the shop using a 20" box fan and some furnace filters. In looking at the filters online, it seems they come in a variety of ratings, but essentially the higher rated ones are more expensive (naturally). Does it make sense to stack the filters to try to improve their lifespan, ie: put a lower rated one and a higher rated one inline, to try to capture the bigger particles first in the cheaper filter? Or am I overthinking this, and should I just buy one of those ones that hang from the ceiling? How much of an ongoing cost is it to replace filters in those? Quote Link to comment Share on other sites More sharing options...
Just Bob Posted December 25, 2017 Report Share Posted December 25, 2017 It would be easier to just buy a unit than build one. The on going costs arent very much. I replaced the outer filter in mine with a washable one I bought at Woodcraft. The inner filter has to be replaced every couple of years, but they don't cost alot. Quote Link to comment Share on other sites More sharing options...
Mark J Posted December 25, 2017 Report Share Posted December 25, 2017 What Just Bob said. Yes it makes sense to pass the air through a coarse filter before the fine filter which is what the msnufactured units do. These filters represent a significant "load" on the fan and an ordinary dime store box fan does not have enough "power" to move a significant volume of air through the filters. By comparison, the Jet air filtration unit's fan draws 5 or 6 amps. I have actually tried the box fan idea with one filter. Placed inches away from where I was hand sanding some of the dust would be drawn to the filter. Quote Link to comment Share on other sites More sharing options...
gee-dub Posted December 25, 2017 Report Share Posted December 25, 2017 I have a nice shop made unit. Despite that, I would buy if I were to do it again. The superiority of even a medium quality unit that is engineered as a unit should not be discounted. Noise levels, efficiency, re-usable filter media, etc. Plenty of folks who built their own speakers will swear they sound better than commercial units. This is rarely true . . . and I imagine the same applies to shop made ambient filters . . . yes, even mine . Dad has the JDS 750 which at the time he bought was always the winner in the bake-offs at that tier. Several makers now have similarly performing units but, price is not always the indicator of performance. This FWW article is July/August 2010 but, if you search a bit I imagine you could find a more current version. Dad got the washable filter for a few bucks extra and it has performed well for over a decade with semi annual cleanings. Remember to scale the unit to your shop's volume to assure satisfaction. Quote Link to comment Share on other sites More sharing options...
Tom King Posted December 25, 2017 Report Share Posted December 25, 2017 A 20" box fan doesn't have the power to pull much air through a filter. Having said that, I have had a use for such a setup. I had a job that required a lot of fitting small tenons with the finest grade of Iwasaki wood file. Just doing a few wouldn't put much dust in the air, but the dust was so fine that it did hang in the air enough to accumulate doing a bunch of them. I put a cheap filter on a box fan, and ran it close to where I was sitting, doing the filing, with fan pointing downward at about a 45 degree angle as close to the filing as possible, but still leaving plenty of room to work. It made a tremendous difference, and there was no noticeable fine dust anywhere but on the filter. I bought the cheapest 20 x 20 filter, and used copper wire to tie it to the fan grill in the corners, just poked through the filter, and around the cardboard edges. Quote Link to comment Share on other sites More sharing options...
Art Posted December 25, 2017 Author Report Share Posted December 25, 2017 Thanks for all the replies. Now that you've all said it, I realize it makes much more sense to buy one. Why re-invent the wheel? Quote Link to comment Share on other sites More sharing options...
AceHoleInOne Posted December 27, 2017 Report Share Posted December 27, 2017 I used an attic fan, made a plywood box and cut an opening for the fan and on either end to pull air in, then attached 2 20x20 3m furnace filters, one to each side. Go ahead, make one. -Ace- Quote Link to comment Share on other sites More sharing options...
wdwerker Posted December 27, 2017 Report Share Posted December 27, 2017 That gives me an idea ! (4) - 24 x 24 filters would cover one face of my warehouse fan ..... Quote Link to comment Share on other sites More sharing options...
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