Shop-Built Sanding Table

A furnace blower makes a good fan. Filter bags keep dust out of the motor. May 28, 2006

I am trying to build a sanding table to use in a high school woodshop. I have been searching for the right fan/blower for quite a while. I have talked to a cabinet shop who uses a rear draft design and a 5-7hp motor (this was about all the info I could get out of them). I cannot seem to find a fan for less than $5000, mainly because I think it needs to be hazard-proof. I have spoken to many fan/blower vendors and am out of ideas. Any thoughts on fans, vendors or tables anyone is already using would be appreciated. I have considered a commercial downdraft, but want a bigger area to sand in.

Forum Responses
(WOODnetWORK Forum)
From contributor B:
Many people use furnace blowers for this purpose. There are even some commercially available units with furnace blowers.

From the original questioner:
Do you know how they deal with the combination of the dust and the electric motor? And do you have any idea about the cfm range?

From contributor B:
These are large blower motors that are running on 110v. So they can't be larger then 2 hp typically. I suspect it's more in the 1/2 hp to 1 hp range.

Dust is taken care of by filters below the sanding surface. This gets out enough of the dust so as to basically protect the motor area from explosion. I'm not sure if the motors are totally enclosed or not.

From contributor T:
Mine uses 1 micron dust collector bags as filters. 8 small ones hang down through 8 matching holes under the table's top. Table is 4' x8'. The motor is under them with a large furnace blower. It is basically a sealed box in which air is drawn through the filters and out the blower. No dust gets past the filter bags. The more filter area you use, the better the filtration and air flow.

Your next problem will be what to do with all the air blasting out of it. Mine is about 2400 cfm and it is only 1 hp! 5+ hp would have to be ducted away somewhere. Do it so that a cross-shop airflow is created, thereby cleaning the air constantly. Mine is ducted into the shop's basement, creating an airflow up the open stairwell and back into the shop. This also helps to cool the shop. You need to talk to an HVAC supplier and get the cfm ratings for different motor/blower combinations. I think 2 or 3 hp is plenty. Make sure your filter medium is 1 micron, otherwise you will create a huge fine dust blower. Very unhealthy. Hope this helps. Mine has been working daily, on all day, for 3 years. Old motor (circa 1960) died this spring. New motor will last another 5+ years I'm sure.

From contributor J:
You should just buy a unit. Look up Denray on the web. They have a lot of options for complete units.

From contributor J:
You need a tube axial fan. You can buy them from Grainger. You can buy a 24" with 1 1/2hp explosion proof motor for about 1200.00. Or you might be able to get a used one.

From contributor S:
There was a short bit in one of the special issues of Wood magazine recently (the entire issue was dedicated to shop projects like benches, cabinets, mobile storage, etc). It had a pretty nice design for a home-built sanding downdraft table that used a furnace blower fan and a 2 stage filter. The guy had it on casters and it doubled as his table saw outfeed table and it had some storage in it also for his hand sanders and paper. Looked pretty nice. I'm going to talk to my HVAC friend to see if he can get me a used furnace blower fan so I can build one of similar design.