MDF and it's little secrets

[cooky1257]

If you were working MDF day in day out it's wise to be very cautious(ply too btw) but one off projects in an open garage say, I wouldn't be too worried except when routing, mask is mandatory

really. Edges are an issue in finishing-so I veneer or only have exposed edges on the rear.

[NickH]

Did some research on this out gassing problem. And the problem is not limited to mdf. These glues are used to make interior and exterior grade plywoods too. The rates of out gassing do increase with temperature. But as I thought these rates are very small. Max rates for mdf are around 2 milligrams per square meter. But the rates for plywood aren't much lower. The rate of outgassing decreases with time. I don't know if its linear rate of change or not though, but I'd bet its logarithmic.

I'd bet most of this stinkyness happens while its sitting at the store or during transportation to the store. That being said a dust mask won't do anything to protect you from the formaldehyde while your working with the material. You needs a respirator that filters organic compounds.

Nick

[cosmos]

It's sad really.. MDF is nice material in most respects to work with, but virtually any time I spend a good part of the day cutting it, I get sick for a few days after.. and I mean stay home from work sick with massive headache and flu like symptoms, even with a dust mask and collection going. I have now banned it from my workshop.

I will have to check out Novaply and hospital grade MDF. Never heard of either material before. Thanks!

4313B, do you know where to get Novaply locally?

[just4kinks]

I forgot how awesome your 4345's turned out. What thickness BB did you use?

I used 1" (actually 24mm) throughout with more bracing than the stock design.

My plan for today was to sandwich two 0.75" sheets together to hopefully achieve a similar deadness of MDF. Bracing would be the same as the stock M2.

Have you considered doing something fancy like sandwiching a layer of damping material in there as well?

[Mr. Widget]

It's sad really.. MDF is nice material in most respects to work with, but virtually any time I spend a good part of the day cutting it, I get sick for a few days after.. and I mean stay home from work sick with massive headache and flu like symptoms, even with a dust mask and collection going. I have now banned it from my workshop.

I will have to check out Novaply and hospital grade MDF. Never heard of either material before. Thanks!

4313B, do you know where to get Novaply locally?

Look for Medite II. It is a brand of US made formaldehyde free MDF. Also, you may want to get a powered respirator. I use one and while a bit bulky you can wear it all day without getting a hot sweaty face.


Widget

[rdgrimes]

A number of flooring materials also have Formaldehyde in them.

[srm51555]

I used 1" (actually 24mm) throughout with more bracing than the stock design.
Have you considered doing something fancy like sandwiching a layer of damping material in there as well?

I have not, any suggestions for me or others reading?

If you were working MDF day in day out it's wise to be very cautious(ply too btw) but one off projects in an open garage say, I wouldn't be too worried except when routing, mask is mandatory

really. Edges are an issue in finishing-so I veneer or only have exposed edges on the rear.

I found a friend that will CNC the baffle, so that will reduce the working time with it even more. Now it's just controlling the gassing. Painting seems to be the easiest, with sealing the edges with drywall compound before painting. I keep on coming back to MDF when thinking about Mr. Widget's experiment with equivalent plywood cab's vs MDF cab's and clearer midrange from the MDF. Also I haven't found anything to support the fact that if I went thicker it would deaden the cabinet, but the BB does look pretty. All I know I better make my decision soon, it's getting colder by the day here. This might be a can of worms but does everyone glue/screw or just glue?

[srm51555]

Look for Medite II. It is a brand of US made formaldehyde free MDF. Also, you may want to get a powered respirator. I use one and while a bit bulky you can wear it all day without getting a hot sweaty face.


Widget

Did some research on this out gassing problem. And the problem is not limited to mdf. These glues are used to make interior and exterior grade plywoods too. The rates of out gassing do increase with temperature. But as I thought these rates are very small. Max rates for mdf are around 2 milligrams per square meter. But the rates for plywood aren't much lower. The rate of outgassing decreases with time. I don't know if its linear rate of change or not though, but I'd bet its logarithmic.

I'd bet most of this stinkyness happens while its sitting at the store or during transportation to the store. That being said a dust mask won't do anything to protect you from the formaldehyde while your working with the material. You needs a respirator that filters organic compounds.

Nick

If anyone else has any safety tips or tricks please let us know this is all good stuff

[hsosdrum]

I have not, any suggestions for me or others reading?

Auralex makes a limp-mass vinyl sound deadening material for room isolation. It's designed to serve as meat in a drywall sandwich—perhaps it could also be used as the meat in an MDF sandwich?

http://www.auralex.com/product/sheetblok-sound-barrier/

[4343]

... This might be a can of worms but does everyone glue/screw or just glue?

I've done both, the screws are used when I want to make something permanent, I leave them off for experiments. One (unfinished) experiment even has a few panels that were edge glued because they were not big enough. Still holding after 5 years.

You could do a ply shell with MDF lining if you really want the look of the ply, or just need durability for transport. That's what I did for some PA boxes, not a complete liner, but the baffle and slot ports are all MDF, while the outside is all Baltic Birch. I used a case of Liquid Nails coating the inside and all the braces. Easily passes the knuckle test, it's very dead. And it turns out 4 2226's + 2446 can simulate real drums set pretty well using trigger pads...

[Mr. Widget]

You could do a ply shell with MDF lining if you really want the look of the ply, or just need durability for transport. That's what I did for some PA boxes, not a complete liner, but the baffle and slot ports are all MDF, while the outside is all Baltic Birch. I used a case of Liquid Nails coating the inside and all the braces. Easily passes the knuckle test, it's very dead. And it turns out 4 2226's + 2446 can simulate real drums set pretty well using trigger pads...

This reminds me of some subs I built a few years ago for our late friend Scott Fitlin. There are a couple of interesting features to the project.

http://www.audioheritage.org/vbulletin/showthread.php?9812-2242H-Subs-for-Big-Bass


Widget

[DavidF]

I have not, any suggestions for me or others reading?



I found a friend that will CNC the baffle, so that will reduce the working time with it even more. Now it's just controlling the gassing. Painting seems to be the easiest, with sealing the edges with drywall compound before painting. I keep on coming back to MDF when thinking about Mr. Widget's experiment with equivalent plywood cab's vs MDF cab's and clearer midrange from the MDF. Also I haven't found anything to support the fact that if I went thicker it would deaden the cabinet, but the BB does look pretty. All I know I better make my decision soon, it's getting colder by the day here. This might be a can of worms but does everyone glue/screw or just glue?

I generally use MDF for projects. It is cheaper (especially if you make mistakes like I do), generally easier to find and does not splinter like ply. The big thing to learn in working with MDF is that its working surfaces are soft. As mentioned above it creates a fine dust and it sure does dull cutting tools (esp. router bits). But it is the relative softness that is the issue. It cannot be used effectively to provide a finish surface. It will show tooling marks, bumps and dings. Never go near it with a power belt sander. I always use wood veneer as the finish to MDF that provides a good flat surface and covers up surface issues.

As to screws v. glue, I always go with glue and clamps whenever possible. Screws are OK for assembly to set the glue if you don't want or need to invest in a host of clamps. Just don't count on them to hold permanently (for that reason I pull out all screws in the final assembly) and take care with drilling in MDF panel edges.

MDF is a dense material giving it some mass potential in mitigating resonance but it is not very stiff. Quality plywood has better stiffness but is not as dense. I tend to brace an MDF cabinet more so than I would using a good plywood. If you are considering a large enclosure (in terms of width and height) I would recommend using a heavy ply for the baffle and MDF for the remaining panels. Depending upon the design, the driver baffle holes can eat up a good part of the surface area so the stiffness can be important.

Again, it you are intending a painted finish MDF, be prepared for a lot of work to prep the surfaces. I am not sure about drywall compound as a filler. I worry about shrinkage. If you have used it before with good results, then fine.

Finally, I always spray paint the interior. More to capture the dust than to prevent gas seepage.

Good luck and make always make it fun...

[Ducatista47]

When it comes to cutting panels, you might seek a real, non Big Box locally owned lumber yard. There is one near me (a few miles down the street) here in Peoria, Illinois.

It has a cabinet shop and they charge $35/hour to cut. I purchased two sheets of 3/4 inch very high quality MDF and an hour from them for close to $100. I had sketched out the cuts on a piece of paper, old school. Every piece was perfect. They fit on the back seat of my subcompact sedan. I bought a router and a ton of clamps and using Macaroonie's method built what might be the most solid cabinets in the state. Per Ian's advice the baffles were two panels screwed and glued for a 1 1/2 inch thickness.

I don't know how rare a lumber yard like this one is these days, but worth looking for and definitely worth finding. I know this one will disappear when the elderly owner passes away. Lacking any such luck, look for a stand alone cabinet shop, probably much easier to find. Why buy all the dust collection equipment and professionally sized table saw & specialty blade for an occasional project?

Clark

PS Not trying to discourage having a full shop if you do a lot of this. I have visited SAEMAN's (Rick's) shop and it is a wonder what he has done with a tiny garage space. My jaw dropped at the baffle templates (Delrin?) he has made for 4345s, 4350s, etc. Only one is needed for each as you turn it around to get the other channel.

[srm51555]

I've decided to go with the 1" MDF and use the Widget BB "sandwich" later when finishing them. This was a hard decision so thanks for all of your help. The Baltic Birch projects are beautiful, but acoustically I felt I needed to mirror the M2 as close as possible. Having the MDF cut and baffle CNC'd by the people with the proper tools eliminates much of the "dirty work". Maybe Speaker exchange should offer a knock down kit . Paining the wood inside and out should eliminate much of the emissions created. In the end if I decide to build another cabinet it's not like I can't find another JBL woofer that like's ~5cf of space.