Down-draft advice

[Byron Trantham]

Sparky just gave me an idea for a down-draft table. Use my out-feed table on my TS. The out-feed table is made from 3/4" MDF with a Formica overlay. Here's the question. Would there be enough air flow by just drilling a series of 1/4" holes in the existing MDF/Formica or do I need to cut a hole and insert a 1/4" thick piece of material? Is 1" on center hole pattern enough? I've never seen a commercial down-draft unit so I'm just shooting from the hip. I will connect a 4" DC hose to it.

[Jim Becker]

For the most effective downdraft table, you'll need to "engineer" the inards to preseve air flow to the entire surface; presuming you're intending to use your DC to power it. There was an article or posting I remember from some time ago that had graduated air channels under the surface. It may be more effective to use an old furnace fan and build a stand-alone solution for your outfeed table...this application is more like the ceiling mounted air cleaners than a typical DC hood. The air flow demands are very different!

[Byron Trantham]

For the most effective downdraft table, you'll need to "engineer" the inards to preseve air flow to the entire surface; presuming you're intending to use your DC to power it. There was an article or posting I remember from some time ago that had graduated air channels under the surface. It may be more effective to use an old furnace fan and build a stand-alone solution for your outfeed table...this application is more like the ceiling mounted air cleaners than a typical DC hood. The air flow demands are very different!

Jim, the first one I made is about 30" square and about 5" deep. I used pegboard for the top. The suction was great. The main problem I have is its size - too small. It did pull dust like a champ. In fact it "worked so well" that you couldn't move the project. anyway, I always have problems visualizing air requirements. Maybe I will good to Woodcraft and see if they have one for sale so I can look at what they did.

On another subject, my SCMS dust collection project. I finally finished it and I have to admit I think I have come up with a respectible solution. The PVC pipe, in conjuction with DeWalts modfied dust chute seems to work very well. Take a look at the end result.

http://www.wooddreams.net/images/Big_Images/Shop/CSMS/pvc_added.JPG

[Jim Becker]

Jim, the first one I made is about 30" square and about 5" deep. I used pegboard for the top. The suction was great. The main problem I have is its size - too small. It did pull dust like a champ. In fact it "worked so well" that you couldn't move the project. anyway, I always have problems visualizing air requirements.

The challenge when you go bigger will be getting the air flow "spread out" to give you as much efficiency near the edges as you have in the middle. From what I remember of the article I mentioned, this is where the DC hookup starts to fall down and a local fan/filter combination starts to work better. Even then, the air flow needs to be planned carefully. If I can rediscover the article, I'll pass on the information.

'Glad the DC worked out well on the miter saw...perhaps the hardest tool in the shop to collect from. (Unless you have one of Terry's "jet-engines" powering your DC system!)