Is all MDF created equal?

[Matt Martyn]

With plywoods, the quality and grade varies so much, I was wondering about MDF. I have always just bought it from the BORG's or local hardware stores, but have yet to use MDF for anything other than templates and shop stuff. I have a couple of pieces that I'd like to use it on now because if its stability. So are there different grades of the stuff, or is it all the same?

Thanks.
Matt

[Dan Lee]

My supplier offers ultra-lite and regualr density. I prefer ultra-lite. I have only used MDF for templates, bending forms etc...

[Neal Clayton]

you can get stuff that's more rigid than the home depot stuff at a lumber yard, made from larger particles.

[Prashun Patel]

There exists MDO, Medium density Overlay, which is MDF overlaid on a plywood core. It's more stable than MDF, and has a nice surface for shop-level cabinetry and jigs.

My favorite, though, is phenolic-faced plywood. It's got all the stability of plywood and the slickness of melamine with the surface protection of a laminate. Great stuff. Costs a lot though.

[Tom Walz]

Saying MDf is a lot like saying plywood. covers an awful lot of ground.

In the scientific end of the cutting tool world we buy enough MDF up front to run all the tests we need since there is too much variation from batch to batch, even on the same product from the same plant.

[Jim Becker]

There exists MDO, Medium density Overlay, which is MDF overlaid on a plywood core.

This product is resin-impregnated paper over a plywood core.

[Frank Drew]

Also called signboard (MDO, that is).

[Justin Leiwig]

There is most definitely a difference. When I got started in "woodworking" if you will I used to build speakerboxes for a stereo shop where I installed car stereos. We got our MDF From a hardwood supplier. When I had to do things on my own the MDF From the BORGS was much lighter in color, lighter in weight and tended to flake apart like particle board, whereas the MDF from the hardwood supplier would end up looking like a piece of ripped leather if you broke it apart.

I believe a large part of that has to do with the quality and quantity of resin used in the making of the MDF.

[Bruce Benjamin]

I've used MDF for a few projects with decent results. I've found that the MDF from the Borg stores to be a little different than what my local hardwood/sheetgoods supplier sells. The Borg MDF seems to have more stuff that causes the occasional spark when cutting it than the stuff from my hardwood supplier. In other words, whoever manufactured the Borg stuff wasn't as careful when adding their ingredients.

There are also a couple of other types with the brand names of, "Medex" and, "Medite". They are both made with formaldehyde free resins and they are also water resistant. The cost is a little higher and you may have to special order it but to me it's worth it. I've used the Medex and I think I spent about 30% more for a sheet. But the water resistant qualities combined with the lack of formaldehyde makes it worth it for me. It also seems to hold a screw better. I don't think I'll ever buy the regular stuff again. One of the two brands is supposedly more water resistant than the other but I'm not sure which. A little research or a phone call or two will probably give you the answer.

Bruce

[Thomas S Stockton]

There are a bunch of different versions that all tend to go by trade names, I'll list what I can think of but I'm sure there are others.
Ultra-lite - lighter than normal
Highly refined - the core has a real consistent grain size, they use this for moldings
formaldehyde free- Has no added formaldehyde
water resistant- I'm not sure how water proof it is never used it
Plus you have just your regular old MDF.
I use mostly the highly refined because that is what my supplier carries
Tom

[Peter Quinn]

They make a water proof version now too , maybe that's medex? I bought it as MDX. Soaked some in a bucket for a week, it was unaffected. Nasty stuff to work with dust wise thought. Its made for exterior exposure applications.

Seems like the stuff from the borg is more flaky and chippy than the stuff I used to use at work. Very unscientific I know, just my impression.

I've never heard of a grade used within the category MDF such as exists for plywood.

[jerry feagley]

That water resistant MDF is for exterior application,I have use it for trimming siding,windows,doors... it really does work,but also expensive.

[John Stevens]

I've bought MDF from HD and from my local supplier. I've never seen a brand name on the MDF sold at any HD, but the stuff sold at my local supplier carries the brand name "Trupan." Consistently (for the last 4+ years since I started WW, at least), the Trupan product has a smoother face (especially after applying a clear finish like poly or shellac) and better-looking edge when routed or sawn. Not sure how much that matters to you, but I spring for the "Trupan Light" if I'm making a shop aid that I want to be accurate, decent-looking and long-lasting. Last time I checked, it was about 50% more costly than the HD product.

[Bruce Benjamin]

They make a water proof version now too , maybe that's medex? I bought it as MDX. Soaked some in a bucket for a week, it was unaffected. Nasty stuff to work with dust wise thought. Its made for exterior exposure applications.

Medex??? Hmmm...Never heard of it before this. As I stated earlier in this thread, the Medex is water resistant. It's not water proof. It lists the percent of absorption on their website. I think it's more comparable to exterior grade plywood, which is also not water proof. But for anyone who is opposed to MDF because of it's lack of water resistance the Medex or Medite solves that problem.

Bruce