Working with MDF-Methods?

[Jaze Derr]

I've read conflicting things about working with MDF, and I would like to get some opinions from people who have worked with it more than I have.

Making a simple cabinet case out of 3/4" mdf. Planning on a 1/4" deep rabbet on the top and bottom for the sides to sit into. The back will be full width, not rabbeted into the case.

I have drywall screws, regular wood screws, and nails available. plus glue, of course. Buying special MDF screws is not an option, although I know it's the best way to go. Other than that, how would you join 3/4 MDF? I'm worried about splitting the edges.

[Tony Bilello]

....Making a simple cabinet case out of 3/4" mdf. Planning on a 1/4" deep rabbet on the top and bottom for the sides to sit into. The back will be full width, not rabbeted into the case.
You might want to rethink the rear panel. I would use 1/4" MDF or Luan and rabit it. An MDF cabinet can get very heavy very fast. Also the 'end grain' would be noticable. I might be wrong and misunderstanding your intentions

I have drywall screws, regular wood screws, and nails available. plus glue, of course. Buying special MDF screws is not an option, although I know it's the best way to go. Other than that, how would you join 3/4 MDF? I'm worried about splitting the edges.
I always use drywall screws and never have a problem. Make sure you use the coarse thread and countersing the heads with a countersink bit. I usually glue and screw using Titebond. Usually I dont have a splitting problem with 'end grain' 3/4" MDF as long as I dont get too close to the ends.

Be aware that even smaller cabinets of MDF can be quite heavily and unweildy for one person to handle.

[Michael Flores]

You shouldn't have a problem using MDF. I have built hundreds of speaker boxes out of MDF and never had a box fall apart. Just use regular wood glue and Pre-drill all holes. I use to use 2 inch coarse drywall screws every three inches apart. I know people are saying "Drywall Screws" but in reality the screws aren't holding the box together, the glue is so be generous. You will be surprised on how strong it is with out using rabbet joints. I use to put massive sub woofers in these boxes and even with all that pounding, they held up. Try looking for a melamine supplier cause they usually stock ultra lite MDF. There is a day and night difference between regular and ultra lite.

[Craig Michael]

Glued MDF holds very well. Use a countersink bit for predrilling so you can keep your screw heads flush or slightly countersunk, the mdf is so hard, the screws will not sink themselves as they would in regular wood or plywood. And as others mentioned, the weight of mdf mounts quickly.

[frank shic]

get some help lifting those sheets!

[Jaze Derr]

thanks for the help! It's a small cabinet, only 24 x 18 x 18. Yes, the MDF is HEAVY!! I guess it's a good thing that I can only fit 2 x 4 sheets into my car, because that's all I could carry at once anyhow. I'll try the drywall screws, then.

[glenn bradley]

I have several units made from MDF. The corner joints are very much as you have planned. One of the units rolls all over the shop and gets rack-stressed all the time, been 6 years and no failures. Construction is as follows:

1/4" rabbets.
Glue and screws (more on that later).
Fully rabbeted, recessed 3/4" backs.
1/8" chamfer on exposed edges to avoid chipping.
Full extension drawer glides with BB ply boxed drawers with MDF false fronts for a matched appearance.

Put on your respirator before milling this stuff. The dust is like toxic talc. I read an article long ago about how to avoid splits in MDF when using screws and haven't had a split since:

- The pilot hole should be the diameter of the screw shank so that only the teeth cut into the MDF (now screw shank wedge stress.
- The hole should be a bit deeper than the screw is long to allow a pocket for debris and to avoid the screw forcing its tip into the material.
- The hole should be mildly counter sunk as MDF has that tendency to "volcano" and exert split causing stress as the screw is driven home.
- Make the last turn or so by hand for safety or test your clutch settings if your driver is consistent.

I used drywall screws in the past and now use better screws. The drywall screws work. I just ran out of them once I started buying quality fasteners. I have had no failures with the drywall screws. As mentioned, these buggers are heavy but, they were cheap to build and add ballast to my bench so, win-win.

2nd drawer unit 002.jpg2nd drawer unit 013.jpg2nd drawer unit done.jpg2nd drawer unit-acc 010.jpg

[Rich Engelhardt]

I use pocket screws & glue.
I never had much luck keeping the bugle heads of drywall screws from causing problems.

[Ben Franz]

One added note - the dust is not to be believed: very fine and slippery underfoot. I've done a couple of jobs for an employer that involved breaking down whole units of MDF in a shop without dust collection. Dust masks were some help but the shop cleanup was a nightmare. The above advice re glue and coarse thread drywall screws is correct IMO - no need for special screws.

[Rob Sack]

A sharp plywood blade, plenty of dust protection and collection, and a back brace

[frank shic]

oh that's right... the dust could be used in chemical warfare it's that bad! you can also look into confirmat screws:

http://www.mcfeelys.com/tech/confirmat.htm

[Jaze Derr]

You guys have been great! I've got the case together with no splitting, using 1 5/8 drywall screws.

I knew MDF was bad with dust, but this is the largest project I've made with it, and NEVER AGAIN! Not unless I can do it outside, which is not likely to happen. I don't care how much cheaper it is than plywood, this stuff is EN AY ES TEE Y!

I've got MDF dust in places that have never seen the sunlight....

[frank shic]

Good luck that dust sticks to everything!