MDF (Medium Density Fiberboard) - Masonite

Starting a thread on what you need to do when working with this building material. Cutting, Drilling, Joining, Layering, Gluing, Painting etc...

I was thinking seeing as this is the material of choice that a thread with everything you need to know would be a good thing. I'm going to pass along what I've gathered so far from what I've been reading here and perhaps we as a group can fill in the missing pieces..

First a word on safety. Both Masonite and MDF are glue based materials as such anytime you are going to cut or drill into it protection is required for both eyes and mouth. Also as Norm says be sure to read and follow the safety instructions that came with your power tools.

MDF and it's thinner cousin masonite are pretty indispensable when it comes to cockpit construction. Both materials offer a smooth unblemished surface to work with. Both are plentiful easy to find and inexpensive. The look like wood but they are made by pressing out a glue/sawdust mix and baking till solid. As such they aren't wood.

Cutting:

Pretty straight forward. Can be done by hand or your power cutting tool of choice. A fine tooth blade will yield a cleaner cut be it circular saw or jig saw.

Drilling:

Also straight forward. Is it is sawdust essentially cleaning your drill bit although not required will make the work go faster as the bits to clog up from time to time.

Joining:

This is where MDF and Masonite diverge from wood. As they are a pressed board they don't take well to self tapping screws. Best approach is to try a few of these different approaches.

- Joining MDF/Masonite to actual wood: Drill out the MDF product so no tapping is required for the incoming screw. You can even counter sink for neatness sake if you like. Using a drywall or plasterboard screw helps too as threads aren't as tight and allow more material to pass by them (remember the drilling above). If you want to put a pilot hole in the adjoining wood that is fine but remember your pilot hole in the MDF is threadless so the hole you drill in the wood will need to be smaller. Thus... drill a small pilot hole through both then come back and drill a larger hole and counter sink for the MDF. This will save time when putting the pieces together and make for a neater more solid bond.

- Joining MDF/Masonite to itself. Here a pilot hole is a must. As MDF is glued and dense it doesn't take well to self tapping screws preferring to expand or crack rather then adjusting it's shape.

http://www.spax.com/usa/
A search online found this company that makes MDF screws as well as many other types that are sure to be of interest to those builders here. A review if anyone has used them would be cool?

That's all the info I have so far. Anyone with more info please feel free to ad on. I'm hoping for a bit of a database of building materials and contruction techniques for the Shell and Components in a Simpit...

If you need to tap MDF, drill the pilot hole then put epoxy or similar glue into the hole. Let it dry, then re-drill the pilot hole and then tap it. Almost never splits. Works for screws as well. More work, but it works.

What my thought was you could avoid that all together by not allowing the wood screw to drill through the MDF but pass though the MDF. Unless your attaching two MDF pieces together?

BTW the SPAX MDF screws can be found at Lee Valley in Canada.

Painting

I haven't painted MDF yet but I'm thinking a sealant would be a good idea. As it's going to absorb paint pretty readily. Doing a a quick look online I found that CIL Latex Primer is great for both priming and sealing properties. Prime twice with a 220 grit sanding between coats then top coat with CIL Para Latex paint.

http://www.cil.ca/
Website is currently under updates to be re-opening in October.

Gluing Masonite to layer masonite

- Carpenters wood glue works best for that. Allow each layer to cure first before applying the next layer.