World's largest 'Whack-a-Mole' !
Again, Herb, beautifully crafted...have you put it to the test yet?
Just out of curiosity, why does it have to be so deep, top to bottom?

 

that's controlled by the thickness of the bed and the dia of the pickup..

 

Herb...
you gonna put hardware cloth on the bottom side of the deck for small part loss control???

 

Herb, that is a very nice build. You might have too many holes or the holes might be too big. My box is I think too big and the holes are too big. I have it hooked up to my big dust collector and it doesn't seem to be pulling enough air.

 

Haven't got it hooked up yet, so don't know how well it works. Might have to seal off some holes. I will pick up some fittings and flex to do a hook up this week.

The last one I made with 1\2" holes didn't do the job.
@stick 486
no hardware cloth

Thanks for all the comments, I will have some things to think about.

Herb

 

Nice, Herb. I went with my own design a year ago, still works great and with the DC hooked up it really pulls hard and will hold a piece in place if I block off the rest of the holes (easy to do).

David

 

Hmmmmmm!!!

That sure looks like HF gray one handed clamps being used!!

Herb I thought that they went by the wayside a while ago.

 

I think you are right. The mini ones seem to hold fine, it is the large ones like the Irwins that don't hold good, and pinch your hands, good eye.
Herb

 

Herb's project is a beauty. I wonder if you could make the box, then use one of the plastic or metal grids that go on flourescent light fixtures. Then have a couple of thin, rectangular masks with rectangular openings to lay over it, leaving openings just a little larger than the item being sanded? You could add a small chamber below the unit to slide in and store the masks out of harm's way. Just thinking.

I really like Stick's idea of, say a 1/4 or 1/3rd inch wire screen below the grid to strengthen it and catch dropped small parts. I'd also use very light weight materials wherever possible so I didn't get a hernia every time I hauled it out for use.

I think I'd put some very smooth material on the slanted boards to keep sawdust from hanging up on tiny rough spots.

 

Yep, ole Herb gets it!!

rather than seal off some holes....

https://www.rockler.com/non-slip-router-mat

 

After reading this: Dust Collection Research - Downdraft Table

I am not sure it will even work.


I used the Rockler pdf.

25077-Down-Draft-Ezplan2.pdf



It is approximately 27X17X6".

No Hardware Clothe. What small parts are supposed to be able to fall into the box? this is for ROS sanding things larger than the holes. And since it is not made for cleaning the shop air en mass just for creating a negative pressure around a small area where I am sanding, and according to the article above will not work anyway, I may be able to cover part of the top,depending on the size of my piece to adjust the air flow. Thanks for all the comments,and suggestions, I should have done more research before I built this. It was a good exercise in drilling holes,though.:grin::grin:

Herb

 

Nice build Herb. I built one similar to the one David shows a number of years ago. Since it's hooked up to my shop vac, I don't get a lot of downdraft when I sand smaller items. To remedy that, I just put a piece of plastic or some plywood, whatever is handy, to cover most of the exposed holes that are not around the piece that i'm sanding. That increases the airflow through the holes that are left uncovered. Works well enough to get most of the sawdust.

 

I like that idea, I was thinking of a rubber mat like @TwoSkies57 ,Bill suggested too, to keep the material from sliding around also. I could make 2 top panels W/O holes too and just keep the middle one with holes,the others for spares.

I am hooking it up to my 3hp DC with 4" flex which has a lower velocity of air flow, but higher volume. I will figure out some way to get this thing to work.

Herb

 

I well today I completed the downdraft box and all my fear were for naught, I works great. I do have a rubber pad for it coming, but might not even need it. I am happy camper ,it works way better than I had imagined. I did put side boards on it and they makes a big difference.

Herb

 

Tom, a Dust Collector is low velocity and high volume, a shop vac is just the opposite low volume high velocity A dust collector does not increase velocity when it is choked down, it has the same velocity and less volume. So if you say choke a 4" DC down to 2 1/2" you get the same as a 2 1/2" @ the same velocity as before but nearly 1/2 the volume as before.
You can tell by the sound of the DC. Leave the 4" wide open , it is loud making lots of noise, cover the end completely it is half as loud, because the motor and fan are not working hard moving air. Open your fingers and it is half again as loud,the motor and fan are working, but not full rate yet.
You can do the same with an amp meter on the DC line. Start up the DC with all the blast gates closed,(mine reads ) 9.6 a. everything closed, and 11.8 a. everything wide 0pen, which indicates it is working harder moving more air open and decreases when closed.
Herb

 

Thanks Herb. Seems counterintuitive, but it is what it is. So my suggestion is not good so I removed it.

 

I think that is because everyone thinks of a vacuum cleaner that is running at very high speeds compared to a 3750 rpm Dust collector, they are in the router motor range 10,000 rpm or more. And the number of fan blades on a dust collector are at least half what a vacuum cleaner fan has. So you have two different principles of moving a lot of air slowly and a small amount fast.

Herb

 

Forgot to add a picture of my downdraft table. Not even close to Herb's but it's adequate for my small projects.

 

Try it without the mat, or a smaller mat and see if the increases the air flow. Also side boards will help like you never would have guessed.
Herb

 

Sometimes you just have to re-purpose the early designs...
https://3.bp.blogspot.com/-ACoiP8I1...zYIyIM-I/AAAAAAAA1Ao/-D4YpnH6OLIOI4qg5r9yrSKo0CXS3dB1gCLcBGAs/s1600/OACGBox.gif

 

LMAO, Fat cat.
Herb

 

I discovered Bessy had 4 packs of small and medium clamps a few years ago and have gradually replaced all my plastic clamps with them. Still have quite a few HF clamps, but I find my projects are less likely to be torqed out of square using the Bessy's, which have far heavier bars than the HF models of similar size. I've found the packs ranging from $20-$30, often on sale near Christmas. I have a crazy number of clamps, but the super stars are 4 sets of two Jet parallel clamps ranging from 24 to 60 inches--these make case work easier. Again, I was making far more money in those days. I have to tip toe past the clamp section now, keeping a death grip on my wallet.

 

An update on my downdraft box.
I have been using it a lot for small p[projects and it works great. I have noticed a real change for the better in the amount of fine sawdust on things in the shop. I use it with a small rubber pad under the work,some of that non slip drawerliner. That decreases the noise and also keeps the wood from walking around the table top. I have found that the large holes work very well, and the removable side boards do help with concentrating the airflow on the top of the box.

Herb

 

and the removable side boards do help with concentrating the airflow on the top of the box.

????