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Forum topic by De1taE1even posted 06-24-2019 03:35 PM 655 views 0 times favorited 21 replies Add to Favorites Watch
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De1taE1even

44 posts in 416 days


06-24-2019 03:35 PM

Hey everyone, I’ve been reading posts and watching videos about downdraft tables for a couple days now, and I think I’m more confused now than I was before researching.

I’m building an assembly table with a torsion top, which is really easy to convert a section of the top into a downdraft table. Right now my plan is to use one end of the table, using the entire width. The interior dimensions of the downdraft area will be 33” (table width) by 24”. The torsion box is 6” tall. I also planned to install ramps on the inside of the box to reduce the volume, and to help direct airflow. I’d be using my Harbor Freight 2HP dust collector with this table.

Questions:
1) Am I dumb for doing this?
2) Is my dust collector powerful enough for this table?
3) I’ll have to drill the downdraft holes through 2 layers of 3/4” ply (that’s the thickness of the torsion box top). Is this thickness going to cause issues?
4) What would you recommend for the hole sizes/layout?

I do realize question 4 has been asked on other posts/forums, but there’s definitely no consensus answer, so I want to ask again. Maybe since I’ve detailed my design in this post, I might get some better answers.

As always, thanks in advance.


21 replies so far

View Tmanpdx's profile

Tmanpdx

26 posts in 130 days


#1 posted 06-25-2019 05:09 AM

the last thing I’d want near my sanding station is a mobile dust collector taking up valuable real estate.

Put a squirrel cage blower in with (4) 20×20 furnace filters, which can easily removed and cleaned/replaced instead.

Great idea on the torsion box, but I’d make the sanding area the entire size. You need surface area.

here is my design. It’s all MDF except for the top which is 3/4 ply with 3/4 holes drilled all over. it works great.

https://3dwarehouse.sketchup.com/model/aee39fd45632fbc3763940017476942b/Down-Draft-Sanding-Table

You can put tons of drawers in the side and route the air down to the squirrel cage blower – which you can pick up used from any heating & AC contractor for $100.

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pottz

5552 posts in 1403 days


#2 posted 06-25-2019 02:08 PM

i built a down daft sanding table a few years ago using rocklers panels hooked up to my dc with a 4” hose and found it very inefficient for dust collection.i now use my ros with abranet sanding disc’s hooked up to a fein vac and have virtually no dust.more efficient and less clutter in the shop.it works for me.

-- sawdust the bigger the pile the bigger my smile-larry,so cal.

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De1taE1even

44 posts in 416 days


#3 posted 06-25-2019 02:11 PM



the last thing I d want near my sanding station is a mobile dust collector taking up valuable real estate.

My dust collector will be out of the way. I have a 20ft hose that I use. Depending on where I build the outlet on the table, the hose could maybe get in the way a bit, but I don’t think that’s a big deal. Everything in my “shop” will be mobile on casters because it’s just a 3 car garage, that has 2 vehicles in it normally. When I want to spread out, I can back the cars out, and use the whole space, but everything needs to be mobile.

Put a squirrel cage blower in with (4) 20×20 furnace filters, which can easily removed and cleaned/replaced instead.

I’ve definitely thought about it. My uncle is in HVAC, so I’m guessing he has a blower laying around, or could find one, at little-to-no-cost to me. But I already have a pretty powerful dust collector, so I figured I might as well use what I have, and maybe upgrade later if I want. I do have room under the mobile outfeed table to put the blower if I wanted to go that route later.

Great idea on the torsion box, but I d make the sanding area the entire size. You need surface area.

here is my design. It s all MDF except for the top which is 3/4 ply with 3/4 holes drilled all over. it works great.


Thanks for this, I’ll definitely check it out! How big is the blower you use, to have enough suction for a table that big? From everything I’ve read, you need a TON of suction for a table that big. The main reason I planned to restrict the size of my downdraft area was to make sure I had enough suction from my dust collector (or a furnace blower if I went that route in the future).

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De1taE1even

44 posts in 416 days


#4 posted 06-25-2019 02:15 PM



i built a down daft sanding table a few years ago using rocklers panels hooked up to my dc with a 4” hose and found it very inefficient for dust collection.i now use my ros with abranet sanding disc s hooked up to a fein vac and have virtually no dust.more efficient and less clutter in the shop.it works for me.

- pottz


That’s good to know, thanks for the info, and thanks for being honest about your downdraft table results. Sometimes I get the feeling those with DC connected downdraft tables are just saying their setup is awesome, but maybe isn’t as great as they think.

My sanders will be connected to a shop vac when they’re in use as well. The idea is, the connected shop vac will get the majority of heavier dust, and the downdraft would catch some (obviously not all) of the smaller particles.

View Charlie H.'s profile

Charlie H.

377 posts in 1069 days


#5 posted 06-25-2019 02:48 PM

I think a downdraft table is worth having, like most woodworking dust collection systems the more powerful it is the better it will work.
At 33”x24” I think you will be at the very upper limit for the HF dust collector to move enough air but I think it’s definitely worth adding to the dust collection arsenal.
With anything less than an industrial downdraft solution power sanders will always need to be connected to a shop vac.
Since there is a HVAC professional in the family that truly has no use for 99 percent of the old blowers I would certainly ask about obtaining the most powerful one he has that operates without the control board.
I would plan to run it as a full time ambient air cleaner as well as a shop fan.

-- Regards, Charlie in Rowlett, TX --------I talk to myself, because sometimes I need expert advice.---------

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De1taE1even

44 posts in 416 days


#6 posted 06-25-2019 02:52 PM



I think a downdraft table is worth having, like most woodworking dust collection systems the more powerful it is the better it will work.
At 33”x24” I think you will be at the very upper limit for the HF dust collector to move enough air but I think it s definitely worth adding to the dust collection arsenal.
With anything less than an industrial downdraft solution power sanders will always need to be connected to a shop vac.
Since there is a HVAC professional in the family that truly has no use for 99 percent of the old blowers I would certainly ask about obtaining the most powerful one he has that operates without the control board.
I would plan to run it as a full time ambient air cleaner as well as a shop fan.

- Charlie H.


Awesome, thanks for the reply! I was thinking the exact same thing, based on the research I’ve done. The HF DC should be at its upper limit, but it should work ok. My main concern is what holes to drill, and spacing, being that the holes will be drilled through 1.5” of plywood, which isn’t a situation I’ve seen much of. My gut is to go with 1/2” holes spaced around 3” apart, but I don’t have a lot of evidence to back that feeling.

Regarding the blower, that’s a great idea, and I’ll reach out to him.

View Tmanpdx's profile

Tmanpdx

26 posts in 130 days


#7 posted 06-25-2019 04:49 PM


How big is the blower you use, to have enough suction for a table that big? From everything I ve read, you need a TON of suction for a table that big. The main reason I planned to restrict the size of my downdraft area was to make sure I had enough suction from my dust collector (or a furnace blower if I went that route in the future).

- De1taE1even

Squirrel cage blowers move a tremendous amount of air. Think about it – they are used to do entire house circulation. The challenge with squirrel cage blowers is you need to give them enough surface area to pull air through.

View Kelly's profile

Kelly

2335 posts in 3363 days


#8 posted 06-25-2019 05:51 PM

My downdraft table is a critical part of my shop. I allows me to sand and carve (e.g., RAM, Foredom) things without a mask. The commercial versions sold to hobbyist or the type most build will not begin to compete with mine.

Like adding trusses to a house, I didn’t feel the need for a torsion box and time has proven that true for my table. If I made it wider, a single support down the middle would be enough support for the wider unit.

Leaving LOTS of foot room under the unit is critical for comfort, when using the station. Keep that in mind, if mounting a blower under the table,

When I sand something, even if it’s at the front edge of my table, you can watch all the dust falling off and running, at a slop, into the table. I even router small items in it and it catches most the dust and chips.

The reason my table works better is just simple physics – I added a top, back and sides, controlling where all the air comes from. Before, having the table was kind of worth while (on the end of a 3hp collector), but it was only marginally impressive. With the back, top and sides closed off, all the air pull is concentrated in the front, rather than from areas that only served to reduce efficiency.

I enlarged all the holes in Masonite, or maybe just drilled them (don’t remember). Anyway, the larger holes helped, but weren’t not made so large they weaken the top.

By adding adjustable height sides and back, then throwing a piece of nylon I had over it, it became every bit as important to me as any other tool in my shop. I use it nearly every time I go to the shop.

The one in the picture works so well I am thinking of selling this one and building a wider one.

It would have flaps on the side that lay down to block off some of the draw, to increase draw.

ALSO, the top would lift to grab that occasional item that falls through, so I don’t have to go around to the back, reach through the 4” port (could be increased to 5” or 6”) and grope for it.

This one has shelf, where my RAM high speed carver sits. A strip of aluminum (yard stick), with spacers behind it mount to the right side, where I hang various pliers and things.

I also have abut six outlets on the side (replaced the strip), so I can leave three of my hand sanders plugged in, as well as the RAM carver and the Foredom (on an IV rack next to the station.

Because the top, back and sides are just air proof/resistant cloth or plastic, it can be lifted to allow sanding of longer things.

The edge of the sides have pipe insulation, so items resting on the edges or back do not get marred.

View Kelly's profile

Kelly

2335 posts in 3363 days


#9 posted 06-25-2019 06:04 PM

You can have pieces of Masonite or paneling to block off the majority of the draw area, until you need it.

I think a downdraft table is worth having, like most woodworking dust collection systems the more powerful it is the better it will work.
At 33”x24” I think you will be at the very upper limit for the HF dust collector to move enough air but I think it s definitely worth adding to the dust collection arsenal.
With anything less than an industrial downdraft solution power sanders will always need to be connected to a shop vac.
Since there is a HVAC professional in the family that truly has no use for 99 percent of the old blowers I would certainly ask about obtaining the most powerful one he has that operates without the control board.
I would plan to run it as a full time ambient air cleaner as well as a shop fan.

- Charlie H.

Awesome, thanks for the reply! I was thinking the exact same thing, based on the research I ve done. The HF DC should be at its upper limit, but it should work ok. My main concern is what holes to drill, and spacing, being that the holes will be drilled through 1.5” of plywood, which isn t a situation I ve seen much of. My gut is to go with 1/2” holes spaced around 3” apart, but I don t have a lot of evidence to back that feeling.

Regarding the blower, that s a great idea, and I ll reach out to him.

- De1taE1even


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De1taE1even

44 posts in 416 days


#10 posted 06-25-2019 06:34 PM

Thanks for all the info Kelly!

I actually already have some ideas for a folding hood that could be secured down by the t-track that I’m installing on the bench. You are one of several people that have advocated the hood, and how much more efficient it makes the sanding station. I’m curious, what dust collector do you have? I spy a cyclone in the background as well, which I’ll probably be installing onto my DC soon as well.

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Kelly

2335 posts in 3363 days


#11 posted 06-25-2019 07:29 PM

I have two three horse, four bag collectors, one with bags up and down and one with canisters up. They are both used Jets I scored off the list. I also have a HF dedicated to the miter and pine cone vacuuming duty.

There is a notable difference in draw between the cans and bags, being even obvious at the tool.

The two four bag beasts are on opposite sides of the shop, to minimize runs, and because I have the room.

I ran the station off a 120 volt Jet with a can and it worked, but not nearly as well as the big boys, of course.

The cyclone is s Super Dust Deputy. That cyclone-collector combo replaced my big cyclone, since they larger units are not fond of being turned off and on, repeatedly, throughout the day, and I didn’t need a stationary monster, after retirement.

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xeddog

242 posts in 3426 days


#12 posted 06-26-2019 03:58 PM

Just a side question. Many I have read about use the downdraft table as an assembly table as well. When assembling, how do you keep small screws, nails, glue caps, etc., from going down the holes in the top, and how do you retrieve them? As droppy as I seem to be getting, half my shop would be down those holes.

Wayne

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De1taE1even

44 posts in 416 days


#13 posted 06-26-2019 04:08 PM



Just a side question. Many I have read about use the downdraft table as an assembly table as well. When assembling, how do you keep small screws, nails, glue caps, etc., from going down the holes in the top, and how do you retrieve them? As droppy as I seem to be getting, half my shop would be down those holes.

Wayne

- xeddog

Great question. From what I’ve seen, people attack it in a couple different ways. For a smaller downdraft area, like I plan to have, you can just reach your arm in through the 4-5” dust port and grab whatever fell through.

If that isn’t a desirable option, I’ve seen two other popular options. 1, to make the top removable. 2, to have a solid cover that sits on top of the downdraft area, only to be removed when downdraft is needed.

Also, many downdraft tables are made from pegboard, or are at least drilled like pegboard, with many small holes, so things falling through those small holes are less likely (though still possible of course).

For me, my DC port will exit the side, and I will have ramps within the box, so any screws, nails, etc that may drop through, will be very easy for me to reach in and grab.

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xeddog

242 posts in 3426 days


#14 posted 06-27-2019 03:08 PM


Great question. From what I ve seen, people attack it in a couple different ways. For a smaller downdraft area, like I plan to have, you can just reach your arm in through the 4-5” dust port and grab whatever fell through.

- De1taE1even

What about lining the underside with a wire mesh or screen? Too much reduction of airflow??

Wayne

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De1taE1even

44 posts in 416 days


#15 posted 06-27-2019 03:45 PM


What about lining the underside with a wire mesh or screen? Too much reduction of airflow??

Wayne

Yep I bet that would work fine! Since my top is 1.5” thick though, it might actually be harder to get the screw out of the hole that it would be to reach into the box through the dust port. :)

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