in a perfect world we'd make all of our projects out of mahogany and Rosewood so all the Woodworkers can brag about only using the finest materials but we don't live in that world and that's why manufactured products such as MDF exist and today I want to share some of the most important things you need to know about medium density fiberboard First It's Not Just Junk wood don't let the hoity-toity froufruit Woodworkers shame you from using MDF you just have to know when to use it and when you shouldn't use it we can make a whole video about that but put simply MDF is great for large panels that you need to stay flat without warping or for one reason or another when you need the stability of a material that doesn't have a natural grain running through it but that natural grain specifically the long bundles of fibers that run down the length of natural wood is what gives natural wood its strength and those are missing in MDF which makes it pretty brittle this really becomes apparent when you try to join two pieces of MDF together remember MDF has essentially sawdust mixed with resin and compressed into sheets you're only gluing the outer bits of sawdust on one piece to the outer bits of sawdust on another piece there's very little structural Integrity there so you might decide to add some screws to strengthen that joint that's when you'll learn what the D in MDF stands for density the fibers are already compressed as much as they're going to endure so a screw can become a wedge that forces those fibers apart and splits your wood very easily if you're going to use mechanical Fasteners with MDF you must drill a properly sized pilot hole properly size means that your drill bit should be the same size as the solid shaft in the center of the screw not the threads but the shaft in the center then the hole you drill will make room for that shaft while the threads themselves can bite into and grip the MDF fibers inside the hole choosing the right screw is important too coarse threads are going to hold on to those fibers more securely than a fine Threaded Screw will and be careful that you don't over tighten your screw when the screw head seats on the surface of the piece stop driving or the threads will tear the fibers inside the hole and there'll be nothing left to grip for this reason I highly recommend using a cordless drill not an impact driver and slow down as the head gets near the surface so you can feel when it's seated and stop at that point really the best way to join two pieces of MDF is with a mechanical joint such as a dado or a rabbit if you have the tools and the ability to create that type of joinery we have tutorials for that sort of thing on our Channel assembling MDF project Parts is one thing but cutting MDF is something else for one thing it is highly abrasive which means it will dull your cutting tools quickly that may be fine if you're using a cheap circular saw blade but I really wouldn't recommend cutting a lot of MDF with your best table saw blade and if you plan to run a bunch of profiles in MDF panels you might want to buy a cheap router bit just for that project so you can throw it away when you're done because it's likely to be pretty dull MDF is also notoriously Dusty when you cut it and the chemicals contained inside can really be harmful to your lungs you absolutely need a dust mask when you're cutting MDF and I don't mean one of those cheap surgical masks you need at least n95 and it should fit your face without leaks around your nose or cheeks it's also a good idea to wear safety goggles that seal around your eyes especially if you intend to do a lot of cutting or sanding with MDF now keep in mind that the danger doesn't end when you turn your saw or sander off MDF dust lingers in the air for a long time and if that dust has built up on the floor or your tools it'll continue to be agitated back into the air As you move around your shop so when you're done with the tools leave the mask on and get out the vacuum don't forget your clothing you don't want to take that into the house with you speaking of sanding while the surface of MDF feels very smooth the edges are considerably rougher this comes from the manufacturing process and it's why you have to pay special attention to those edges if you intend to paint or put some finish on other than an edge banding I don't want to make a full tutorial about painting here but I will say you have to sand and prime the edges if you want them to be as smooth under paint as the surfaces in fact you might follow a multi-step process first sand the edges to 220 grit then apply drywall joint compound use a putty to press it into the fibers in the edges if you have a lot of identical Parts you might stack a bunch together and do all the edges at once now when that filler is dry lightly sand again with two triny grit then put on some primer the fibers are going to soak up that primer and the edges will be a little rough again just lightly sand them smooth with 220 and you'll have a glassy surface ready to paint MDF can be great for a lot of projects just don't overuse it if it's something that will never be moved like built-in cabinets then MDF might be a good choice but if it's a piece of furniture that's likely to be moved around maybe even after you're gone if you want it to last you better make it out of solid wood especially the joints if you have some more tips about working with MDF please leave them below and I'll talk to you next time my woodcutters.com is the sort of small business I like to support Stefan is a great guy and he can find you knives and Cutters for almost any Joiner plane or shaper or molding machine and his are the best prices if you're planning to upgrade to a helical carbide cutter head please use the link below this video to check with him before you buy somewhere else some small businesses are just worth supporting
