Make Dust Collection Ducting from MDF?

[Kevin Honkomp]

Newbie here. I have a Penn Central 1 HP dust collector that I bought on Craigslist. Moving it from machine to machine got old in a hurry. As I started researching a replacement I've become more and more freaked out about the fine dust issue. I'm going to upgrade to either a Clear Vue CV1800 or an Oneida V5000. I can afford that. What I can't afford is an additional $2,000 or so for duct work. No local supplier for either metal or PVC that gets me in for much less than that.

What I got for nothing (long story) is 100s of feet of MDF 3/4 x 16" shelving. It would be pretty simple to make rectangular ducting out of that. As far as I can find, it's going to have more turbulence and more friction loss, but it looks to me like I should have excess airflow and speed to run one machine at a time. Bill Pentz, on his site, mentions that Melamine can be used and cautions against using any flammable produce in an attic or crawl space.

Has anyone tried this? I'd be interested in ideas and opinions from anyone who has thought a bit about the ducting issue. Thanks.

[Jamie Buxton]

MDF ducting should work. It'll be a pain to install -- MDF weighs a whole lot more than sheet metal. And you'll have to invent bends and Y's too. But if you have more time than money, why not?

[Chris Padilla]

Where there is a will, there is a way. With some thought, it should work out fine but I gotta say that it sounds painful to do but you'll have your ducting for only your time invested as Jamie said. I'd love to see your progress pics as you venture through this. :)

[Jim Andrew]

Building Y's would be relatively easy. 45's as well. Would you just make the ducting 6x6? Seems it would be a good idea to finish the inside, sand and give a 2nd coat, so the inside would be slick as possible. Going from round to the square duct would not be bad, if you use pipe to get to the duct. Think I would caulk the joints as you assemble the duct. Screws would hold it together tightly.

[Alan Schaffter]

Some big issues:


Square or rectangular duct has more surface area than circular duct with the same cross-sectional area- hence much more surface drag!
3/4" MDF is HEAVY!
Square or rectangular duct has corners which means more turbulence, but can also mean dead areas where dust and chips can settle and accumulate.
It will be a lot of work to build ductwork from MDF and a lot of work to reconfigure when the time comes- and trust me that day will come!
Why not look for some ASTM 2729 thin-walled S&D PVC pipe- it is cheaper, especially fittings, than metal, and cheaper and a lot lighter than plumbing Sched 40!

[Chris Parks]

Here you go....http://spikyfish.com/DustExtraction/

[Keith Outten]

MDF is a porus material, you can pull a vacumn right through it. If you decide to go this way you will have to paint the surface to seal it, otherwise you will be leaking along its entire length.

[Chris Parks]

Keith, I doubt the depression in the ducting would be enough to cause that to happen, certainly not to any measurable level. I would paint the inside anyway to encourage the debris to flow better as the airflow on the sides is slower due to wall to air friction. I think it is a very practical answer if the cost savings are there.

[John Donofrio]

Here you go....http://spikyfish.com/DustExtraction/

It never ceases to amaze me what one will go through to reach a desired goal. That appears to be very well done.

To the OP, after reading the above I would say absolutely go for it if you're willing to put in the effort. BUT... as Alan mentioned above, 3/4" MDF ducting is going to be EXTREMELY heavy.

[Chris Parks]

The ducting in that link is made from 1/8" MDF.

[Mike Wilkins]

Consider PVC plumbing pipe; I did a 30 foot run using the stuff and so far so good. With the pipe and fittings I likely spent less than $50.00 in PVC. The rest of the costs was in blast gates, flexible pipe and home-made hangers.
I am in agreement with others on the use of MDF. Please re-consider.

[Jim Andrew]

Sure would be nice if you could find a local source for the S&D 6" 2729 piping. The price is right, but locally I was not able to find it so went with spiral pipe and fittings. The pipe and fittings cost more than the cyclone.

[Jason Roehl]

Keith, I doubt the depression in the ducting would be enough to cause that to happen, certainly not to any measurable level. I would paint the inside anyway to encourage the debris to flow better as the airflow on the sides is slower due to wall to air friction. I think it is a very practical answer if the cost savings are there.

I doubt you'll find a paint that will last very long in that environment. You'll be basically sand-blasting it every time you use it... A high-quality floor finish with aluminum oxide might fit the bill.

Sewer and drain PVC (usually green) is fairly inexpensive, probably less overall cost than MDF (and all the finish, fasteners and glue you'll need to assemble it).

[Jamie Buxton]

MDF is a porus material, you can pull a vacumn right through it. If you decide to go this way you will have to paint the surface to seal it, otherwise you will be leaking along its entire length.

The porosity of MDF may be an issue if you're trying to make a vacuum press, and your vacuum pump pulls 3 cubic feet per minute. But a typical chip collector pulls a thousand cubic feet per minute. A few little leaks in the duct won't have any effect.

[Alan Schaffter]

I doubt you'll find a paint that will last very long in that environment. You'll be basically sand-blasting it every time you use it... A high-quality floor finish with aluminum oxide might fit the bill.

Sewer and drain PVC (usually green) is fairly inexpensive, probably less overall cost than MDF (and all the finish, fasteners and glue you'll need to assemble it).

Be aware, there are two types of S&D, the green stuff which is SRD35 (ASTM 3034) and the lighter, thinner-walled ASTM 2729. Ideally, the best stuff to use is ASTM 2729 which is variously called "thin-wall S&D", "Solid Perf", etc. Both have the same O.D. so can use the same fittings (NOT not standard Schedule 40 fittings!), but ASTM 2729 has a thinner wall so is somewhat lighter and has a slightly larger I.D. than SDR35.

The blue SDR35 pvc pipe is often found at big box stores, but usually only in 4" (they sell 6" fittings, however?? Go figure :confused:). The fittings for ASTM 2729 are usually found in a separate section by the irrigation and drainage stuff, NOT with the plumbing fittings. You will often see perforated ASTM 2729 drain pipe in big box stores but rarely solid pipe and if they do have it, it will only be in 4". You can usually only find 6" at specialty pipe and irrigation, and landscape suppliers such as John Deere Landscapes.

[Ole Anderson]

Kevin, welcome to the creek!

Wow, two grand worth of duct? Must be a huge shop with lots of drops. If I could attach an Excel spreadsheet, I would share pricing options (Ok I only was looking at snaplock). But I had a main run of 28' of 7", 10' of 6" drops, 30' of 5" drops, and 10' of 4" drops. 5 wyes, 9 large radii adjustable elbows and a couple of reducers and 3 blast gates (I already had several). Done in 2011. Oneida pricing, not including shipping, was nearly $694. I was able to get it locally from an HVAC supply house for just over $222. All 26 gauge or better. It helped considerably that my son got me his employee discount as he managed the HVAC place. But even double it and it still was not 25% of the cost 2 HP SDG.

As far as using the MDF, cutting all of that will make you wish you had your system up and running first. But of you are willing to fab a lot of 22.5 degree bends, wyes and then put a filler in the sharp corners to minimize cust catching areas, it could be done. Yes you will need more hp to overcome the extra losses you will get, but a 5 hp cyclone should get you there.

[Keith Outten]

You can't pull a vacuum on a sponge. Some people use MDF spoil boards on CNC Routers so they can pull a vacuum on sheets to hold them down to the table. I realize that a Vacuum system is a different animal than a vacuum hold down system but if you consider an entire collection pipe made from MDF you can expect the loss to be significant.

Another consideration is moisture. MDF absorbs moisture and swells. Running a lot of air through a system when the humidity is high will cause problems. I have to machine my spoil board again and again when the humidity is high in certain seasons...it will not stay flat.
.

[Kevin Honkomp]

Wow, amazing response, thank you all. I get that it would be a pain to do the MDF and I’m still looking for alternatives. Like I said, I got a ton of it (literally more than a ton when I think about it) free so I’m always looking to use it. I’ve also moved it twice so I know how heavy it is. I’m about to retire and would have time to play with it. I’d use it just for the large runs and convert to PVC DWV (ASTM 2729) for 4” and under. That’s readily available here. My preference would be all PVC, but I need some 6” and the only distributor in my area that has it hates selling “consumers” and just avoids it by charging 4 to 6 times retail.
He’s also the only HVAC supplier in town.
The spikyfish link shows sort of what I was thinking, though his sweeps are much more elegant than what I had in mind. Nice job. Would be interesting to know how that worked out for him over time.
Also, I found KenCraft Company when searching this form and everyone had nice things to say about them. They have most of what I need in metal at reasonable prices, might be able to get the stuff they don’t have, and are working up a shipping quote. Thanks again for your thoughts.

Kevin