# Down draft blower for dust control



## John Thomson (Aug 21, 2015)

Hi all. I'm new to these forums. I have a question on setting up a dust control system. I have been using a shop vac for dust control "after the fact." I have an old Jennair down draft cooktop that has been sitting in my garage since I replaced it. I have a hard time throwing things away!

Have any of you tried using a blower like this to power a dust control system? It's a squirrel cage type of fan with a variable speed motor. I have no idea what HP but can probably find it somewhere on the housing or look it up on a parts website. I would envision having to install a cyclone and bag house between the blower and the dust intake. 

Do you think it's worth it or just a waste of time?


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## Mike (Nov 22, 2004)

I suspect there would not be enough air flow for dust collection John. Might be ok for a paint booth if vented outside. Use a pleated filter if you try this.  Or perhaps a down draft sanding station?


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## Nickp (Dec 4, 2012)

Welcome, John...

Can't tell by your profile what tools you have but, in general, you will need a hefty amount of CFM to collect dust and chips "before the fact"... You might achieve this better with the shop vac and a separater. Something like the Dust Deputy between your tool and the shop vac...assuming your shop vac is strong enough.

The Jennair might be useful as an air filtration but likely requires a box, filter, etc...

Describe a bit more what you have available...you will get plenty of ideas from the forum...

Do a forum search for "dust collection" and you will see lots of posts already...ask away for help in setting your system up...the members enjoy helping...


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## hawkeye10 (Jul 28, 2015)

I have not used a down draft cook top but I think you could use it. What about a down draft sanding table. You can look on Youtube for one that you like. They are easy to make.

Don


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## John Thomson (Aug 21, 2015)

Thanks for the suggestions and advice. I especially like the thought of a sanding table or paint booth. I'll look for a video.


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## PhilBa (Sep 25, 2014)

Yeah, my first thought was a DD table for sanding. Those blowers are usually 1000 cfm or more so it might well be a good choice. They can be noisy so you will want to insulate. I've seen a number of designs that could be adapted. Google downdraft sanding table designs for lots of ideas.

You should give thought to incorporating a HEPA filter. Sanding produces the worst kind of dust. Your lungs will thank you! You may want to consider a pre-separator or pre-filter to make the HEPA filter last longer.

I've thought about building a DD sanding table and even drew up a design that integrated it into a torsion box assembly table but in the end decided not build due to space needs in my shop. Plus, I've got pretty good sanding dust collection at the tool via a shop vac/pre-separator/HEPA filter.


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## Mike (Nov 22, 2004)

John, Rockler sells a product that works as a grip surface when painted onto pegboard. I am building several of these downdraft sanding tables this weekend if everything goes according to plan and will post photos. I will get you the Rockler part number.


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## DaninVan (Jan 1, 2012)

What Phil said! I don't remember the Jennair downdraft units as being especially noisy(?). Mostly wind noise. In an enclosed box assembly you won't even hear it, especially with a sander running.
_Make sure you thoroughly degrease it_...the sawdust will stick to it like snot if you don't.


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## DesertRatTom (Jul 3, 2012)

Thanks for the ideas. I'm working on a way to collect as much sawdust as possible from behind and around my sliding miter. Since it sits in one spot, I'm thinking of using a shower curtain I can pull up around the saw, then fastening it at the bottom to a collection box. A big blower with a coarse filter on the input side, and a fine filter on the output side, then exhaust into the back yard after that. There is plenty of room for most of it behind the saw for this application. Maybe a 6 inch pipe to the outside. That tool is the worst offender in my shop, and my dust collection system just won't suck it up from behind the saw.


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## PhilBa (Sep 25, 2014)

Yeah, the miter saw is a tough one to collect from. There are lots of schemes out there and none of them are that effective.

One thing I've found, if you "chop" (i.e. drop the saw down onto the work) the dust goes everywhere. However, if you slide into the cut, a lot more of the dust is channeled into the collector port on the top of the saw. A shopvac can pick that up. I think it's because a) the blade is less exposed during sliding, b) the cut is more vertical (aimed at the guard) and c) the guard is closer to the actual cut. So, I try to slide rather than chop where ever possible. Try it.


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## 163481 (Jul 8, 2015)

One thing I've noticed about squirrel cage impellers: The vanes are often spaced about 1/4" apart that that may not be suitable for a larger chip maker like a lathe, planer, jointer, etc. There are articles on the 'net about DIY larger impellers for dust collection systems, often in connection with some kind of separator like a cyclone or Thien baffle.


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## Mike (Nov 22, 2004)

Right Chuck, but my suggestion for a down draft sanding table would be only fines that are easily handled.


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## DesertRatTom (Jul 3, 2012)

PhilBa said:


> Yeah, the miter saw is a tough one to collect from. There are lots of schemes out there and none of them are that effective.
> 
> One thing I've found, if you "chop" (i.e. drop the saw down onto the work) the dust goes everywhere. However, if you slide into the cut, a lot more of the dust is channeled into the collector port on the top of the saw. A shopvac can pick that up. I think it's because a) the blade is less exposed during sliding, b) the cut is more vertical (aimed at the guard) and c) the guard is closer to the actual cut. So, I try to slide rather than chop where ever possible. Try it.


I was watching several guys on youtube doing that, and have begun sliding forward, then back through the piece and there does seem to be less scatter. I've been working on the shop to control the dust better and make it easier to clean up. Everything you can do to control sawdust is worth doing so far as I'm concerned.


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## DesertRatTom (Jul 3, 2012)

Some time ago I saw a cabinet that was set up for dust collection that used a very large squirrel cage impeller. There were two stages to it. On the bottom was a drawer style bin that collected the larger dust and bits and pieces. A filter, then the second chamber were the fine dust was trapped, then another fine filter, then the blower itself. It all ported out from there into the open air through a very large (8 inch) PVC to the outside. But the blower was very large and moved a lot of air. My swamp cooler pumps 4500 cfpm into the house at top speed. Saw blowers of this type on Amazon. That is a lot of air.


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## DaninVan (Jan 1, 2012)

Yeh, especially when you just paid to heat it! :0


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## DesertRatTom (Jul 3, 2012)

DaninVan said:


> Yeh, especially when you just paid to heat it! :0


I only run the DC when I'm cutting, but we have very hot summers and very cold winters, so I know what you're saying. For airborne dust, I run a 20 inch fan and a filter to gradually suck it up. Finally changed the filter on it the other day (it is in an enclosed box) and was surprised at how much very fine dust it had captured. I leave it running for 3-4 hours at a time.

Used to have a 5 micron filter bag inside the shop, but now by porting the final output outside, the air is far less dusty.


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