Downdraft Sanding Tables
Cabinetmakers sing the praises of downdraft sanding tables, and discuss whether it's worth building your own. November 20, 2005
Anyone here use downdraft tables in their shops? I'm looking at some made by Sand Pro and wonder if they're worth the investment. I'm tired of all the sanding dust.
From contributor I:
I've never used a downdraft table, but they seem like a waste of money to me unless you're doing a lot of hand sanding. If you're using a regular old orbital sander or belt sander or whatever power tool it may be, just use a vacuum. Fein are the best, but shop vacs are really cheap given their performance and are sold at most hardware stores.
From contributor G:
You can also build a sanding table at whatever height you like and fill the top with holes. Then make a header and tie it into your shop dust collector system.
From contributor J:
We have 5 downdraft tables from SandPro and they work great. Dramatically cuts down on dust floating in the air (whitewood sanding), finish room is cleaner (sealer sanding) and our insurance agent loved seeing them!
From contributor A:
To add to contributor G's post, it is important that, if you make your own, you also include a baffle on the inside bottom to direct air flow, otherwise, you won't get even airflow from the front (i.e. the side where the dust collection is attached) to the back.
From contributor L:
We've got a 4x8' table with a big fan and 24 filter bags. It has holes around the sides, too, and it works great. We built a muffler for it to cut the noise. We made holding blocks that fit in the table holes to trap the work piece.
From contributor R:
I have wanted to build a table like that for my shop for some time now. I have an Oneida dust collector with a cartridge filter that I plan on using for the vacuum, but I'm unsure how to design the baffle to get even airflow, and I would like to put some kind of coating on the grid to prevent scratching and slippage of the work piece. Any advice would be a great help.
From contributor S:
They are worth every penny. It creates a healthier breathing environment, better finish conditions, and less cleanup in shop. Spend the extra money on a self cleaning system. I wish that we did.
Denray had a new filtering system out that was on display at AWFS. It actually costs less than the 4x8 table we bought a few years ago and it is much more efficient. I was very impressed. They also have sanding booths if you really want a great system. In my opinion, it is not worth the time to build your own.
From contributor D:
We have 14 Sand Pro downdraft tables. They are very good. You don't realize how good they are until you sand on a regular table again. Very quiet.
From contributor O:
I bought two Sandpro tables at the Vegas show. Had them for two days and just ordered a third today. Anybody who says they are a waste obviously has not used one. I had a shop-built table that I thought worked very well until I got my Sandpros. If you build one, you have to be honest to yourself and ask if you can really reinvent the wheel and build one cheaper. Buy one and spend the extra time you would spend building a lesser table on a money making shop job.
From contributor A:
Contributor R, the baffle is basically a false bottom that sits at an angle. It starts at the top of the far end (i.e. the side directly opposite the dust collector opening) and slopes down underneath the opening for the dust collector. That is really it. It forces the air farthest away from the dust collector opening, the top of the baffle, to flow faster because of the decreased air space. It is trying to change out the same cubic footage of air per minute, but there is less air to change out. Therefore, it compensates by making the air flow faster. Another thing that a baffle does, if you think of efficiency in terms of CFMs, is effectively cut the air space in half. More importantly, it closes off the dead air space (the air space that is not conducive to change) to increase down draft efficiency. So, instead of trying to change out, say, 9 cubic feet of air in a 9 cubic foot down draft table, it is now changing out 4.5 cubic feet of air twice as fast in the same 9 cubic foot table. I have never tried it, but you could also baffle the two sides adjacent to the dust collector opening as well. You will be left with what is basically an inverted, three sided pyramid.
From contributor V:
Since dust is a carcinogen and most airborne dust is smaller than the eye can see, do you really know how much you are breathing?
Dust tables using the pleated type furnace filters will capture only about 70% of dust at 3 microns and larger. Some companies will advertise capture down to 1 micron. They will, but only about 20% - the rest that is that small or smaller will go through the filters. I saw Denray tables at AWFS at Las Vegas. Their new table is awesome - that filtration system captures 99% of 1 micron and larger and the dust falls down into a drawer, leaving only the dust drawer to dump. No filters to pull out and clean, easy and no mess.
Of course, their cartridge filters clean to 99.97% efficiency at 1/2 micron. High blood pressure and dust have one thing in common. They are both silent killers. It is what you don't see that kills you. The smallest black dot on a white piece of paper that can be seen with perfect eye vision is 10 microns in size - that is with contrasting colors. To see dust in the air floating is like seeing fog. Millions of micron and submicron droplets of water floating.
Back to the first question - yes, downdraft tables are beneficial, and before you build or buy, call the professionals and find out the differences in the fans and filters. Watch out when companies advertise CFM. Some companies advertise free air and some advertise 1 or 2 inch static pressure rating. Don't get fooled. There can be a large range in actual CFM ratings, so know what you are buying. Check out Denray.