Do Simple Downdraft Tables Work?

[LarryG]

There are two basic kinds of downdraft sanding tables: the full-blown kind consisting of a largish cabinet with a blower motor concealed within it, and the quick-and-dirty pegboard-topped kind that hooks up to either a shop vac or, preferably, a dust collector.

My question concerns the latter. Those of you who have built one of these simple boxes with a perforated top ... does it work well? Does it provide a significant improvement over simply hooking the hose to the sander itself?

And whether it works or not, do you power it with a shop vac, or a full-size DC system? (IOW, does it maybe not work because you use a shop vac ... or still not work even though you use a DC?)

Reason for asking is that I'm currently working on an extension wing for my BT, and I'm considering making it do double-duty as a downdraft table that can be connected to my HF 2HP DC. But if these simple designs don't really work very well, I probably won't bother.

Thanks very much!

[Tom Miller]

Their efficacy (word of the day) largely depends on size of parts vs. size of table and airflow. In general, I think you still need to use the DC port of your sander, especially for the larger parts.

The first pane of the diagram below shows how the dust from smaller parts will be influenced by the downdraft airflow before they have a chance to escape. Sanding larger parts means there's more chance for dust to escape upwards before being influenced by the downdraft air flow.




Seems to me that most of the dust that escapes from an ROS is from the ROS going over the edge of the workpiece. Here, the downdraft table will do a great job of collecting.

I made a 2' x 4' downdraft table with a pegboard-top with holes enlarged to 3/8". It's in a 5 - 6" deep frame, and I have a 4" DC port attached to it. One of these days I'll have to try a smoke test to see how well it works, or rather, to gauge its efficacy (that's two -- eight more to go today).

Regards,
Tom

[Ken Massingale]

I agree with Tom on the large pieces. Most of the dust escapes. Mine, connected to the HF DC doesn't work at all most of the time 'Cause I forget to drag it out and use it! Seriously, I do most sanding underneath the input side of the overhead air collector. That, and remembering to attach a vac to the sanders DC port gets 'a lot' of the dust. I'm resigned to a through blowing and vacuuming of the back of the shop after each sanding session.
ken

[rickd]

hi,

larry, thanks for asking that question - i have been wondering about the exact same thing - and thanks, tom, for the detailed answer - that was great info.

i'm not too sure where that leaves me though as far as a downdraft table goes. i think for now i just might keep doing what i do now - open the overhead garage door and do my sanding outside on a mobile table. it's warm enough outside even most winter days as long as it isn't raining.

[bigsteel15]

hi,
it's warm enough outside even most winter days as long as it isn't raining.

That doesn't leave you many days to work outside...LOL

[rickd]

That doesn't leave you many days to work outside...LOL

that's absoultely right - the weather here's the worst in all of canada - so, whatever you do, don't move to vancouver island ! you're welcome to come for a visit though - just remember to get a return ticket before you leave

[drumpriest]

My DC setup for sanding is just the port on my sander to my shop vac with a hepa filter, and my ambient air cleaner running. Honestly this does a pretty darned good job. I still use a mask when sanding, but when I've taken the mask off to see how bad the dust is, it's not been bad at all.

I was actually surprised at how well the dust port on my bosch sander works. There is still dust to tack off, but nowhere near as much.

[lrogers]

I think they work best when combind with the sanders dust port. A side benefit, is that the suction helps hold the pieces in place.
I think mine works best when hooked to the DC instead of the shop vac.

[gtokarski]

I hope you are still using some sort of air filter/respirator when you sand.