Working with MDF

[Stewart Crick]

Have an MDF project coming up and I've never really worked with MDF before, so I have a question. The project calls for some varying thicknesses of MDF (i.e.: 3/16", 1/2"). Can I just run this stuff through my planer? Does it machine like regular wood?

Stu

[John Miliunas]

Can I just run this stuff through my planer? Does it machine like regular wood?

Stu

:eek: :eek: :eek: Eeeeeeek! NO! Please don't! :eek: Well, I guess you could, but you'd have one heckuva' mess on your hands! :D MDF has a "protective" layer on both sides to keep all that compressed fiber together. You remove it and you can kiss that sheet goodbye! Get the seperate thickness sheets and just save whatever you don't use for the next project. In the grand scope of things, mdf is pretty cheap to begin with. :cool:

[Jamie Buxton]

John's right -- MDF typically has higher density near the faces. If you plane it off, you're looking at a surface which is somewhat softer and furrier. If you're going to paint this surface, you'll probably want to prime, sand, and prime again. Buying sheets in the thickness you need is better. However, if you need odd sizes -- for instance the 3/16" you mention -- you may have to resaw it or plane it. Standard tools do work with MDF, and you can run it through the planer.

Two other tips:
* MDF dust is amazing. It is very fine, goes everywhere, and hangs in the air forever. The dust is also very slippery, and can make a shop floor feel like ice. Good dust collection and a respirator are very helpful.
* Water-borne finishes can raise the "grain" a lot. An oil-based primer is good, or for faster drying shellac (like Zinsser).

[Stewart Crick]

Thanks John and Jamie! Quess I'll do a little experimenting when th e time comes.

Stu

[John Miliunas]

One other tip, if I may: MDF is really not that far off from being a sponge! Seriously! Be sure to protect all the ends with some type of sealer. Like Jamie mentions, shellac does nice or I've even used oil-based poly. Anything that is exposed, even routed edges, should really get hit with some type of protectant, as moisture will otherwise absorb into it, swell the material and often disintegrate not too long after. :cool:

[Tim Morton]

From my days of building speaker boxes, I have also found MDF to be very rough on saw blades. You will dull them faster with MDF. And wear a dust mask..unless you find you don't have enough Formaldehyde in your system...if you can try and find a proiduct called medite...its a higher density formulation of MDF and Formaldehyde free. Its also heavier than lead.

[Mark Singer]

There is a "light" MDF which is a lot nicer to work with...Easier on the back! Just as refreshing!

[Jamie Buxton]

At least in my area, light-weight MDF costs significantly more than standard MDF. In fact, for only a couple more dollars a sheet, I can buy shop-grade maple ply. Given that choice, I'll buy plywood every time. Plywood is stiffer, doesn't cold-flow, and is much much much nicer to work with. And you might be able to use scraps in a varnished piece -- something you'd never do with MDF.

IMHO, MDF makes sense only if you're a big production line. There, materials are the dominant part of the budget. Saving a few bucks per sheet is a big deal. However, in a small shop, materials costs are a much smaller portion of the budget. It makes lots less sense to force yourself to work with that nasty stuff.