Working with MDF?

paperclap

Hi all,

So long story short, I’m planning on building a set of built-in cupboards in our bedroom. Floor to ceiling, wall to wall. Rough plans attached!

I’m going to create a plinth made up of 25mm by 150mm redwood.

But for the carcasses, I’m planning on using 18mm MDF. For the doors, 12mm MDF.

I don’t have a great deal of experience working with MDF… but have heard it has a horrible tendency to split. Much more so than wood.

I think drilling pilot holes is a given. But, is there a better screw to use? Are MDF screws far superior than regular wood screws? I’ve heard good things about the Spax MDF screws?

Had planned on using 4 by 50mm screws (maybe 60mm a better choice?).

Once all screwed and I’m happy with the positioning and fit… dismantle, then wood glue and re-screw.

Any thoughts or advice? Thanks!

ThisIsWeird

Yes, it splits easily - if screwed into it's end/edge. For screwing into MDF's surface, the main issue you'll have is how hard it is!

So, yes, pilot holes for both.

No experience of these screws, but they appear to have the most important factor which is a parallel thread - ie not tapered.

Which parts are you actually planning to screw together? You appear to have a front frame - top rail, sides, bottom rail and two central 'mullions' (no idea what they are called)? For these, I reckon biscuit joints would work best - what were you planning?

That's exactly how I made my MDF doors - 12mm panels, with 12mm stiles glued on top. Since 'Shaker' tyle, I planed a bevel on the top edges of the stiles, and this left a V-groove at the 'joints' to emphasise the bespoke look. You could also consider - your call entirely - using a router to vertically V-groove the central panels to add even more 'Shaker' to it. 

ThisIsWeird

Oh, and dust mask...

SpudGunPaul

Have you considered a pocket hole jig for building the carcasses?

FreeBear

Some 25mm battens in the corners and screws through the MDF and in to the timber. Depending on the depth & width, MDF may not be the best material for shelves - I made a set of cupboards for a bedroom here and put a shelf in between the two (MDF). After a few years of storing a few books on it, there is a very noticeable sag in the middle.

If you are planning on using concealed hinges (as used on kitchen units), you have to be very precise when boring the 35mm holes in 12mm doors - The holes need to be 10-11mm deep, so not a lot of room for errors.

paperclap

Thanks guys.

Sorry, let me clear up a few things.

For the carcasses, I’d planned to screw from the face of the left and right panels, into the end grain of the top and bottom panels. Funnily enough, I had thought of using pocket hole jig. I don’t have one, but was looking the other day, and do love trying new things! But thought “am I just making it more complicated than it needs to be?”. Would it be more beneficial? I’ve heard they’re super strong joins.

For the doors, I’d planned to screw the 12mm rails and 12mm stiles onto the 12mm panel… with wood glue. Detailing to be decided… but a v-groove is certainly a nice, understated feature. Biscuit joins could work nicely actually. Would certainly mean a lot less filling and sanding! But other than less filling, is there any other benefits?

On the MDF sagging issue… have heard that too. But, the largest span would be 1 metre… or maybe even just 50cm. Would a metre run the risk of sagging?

I had planned on using concealed hinges. Also called “Euro hinges” I think? But, the shaker style door will effectively be 24mm in places… and will be 24mm in the hinge area in particular. So hopefully not a problem 

trix-a-belle

SpudGunPaul said:

Have you considered a pocket hole jig for building the carcasses?

As someone who has tried to make up a simple cabinet carcass (nowhere near the size the OP is planning) in MDF with pocket holes I'd say do not go there as it will split. I went for ply in the end

Doozergirl

If you've essentially got 3 x 1000mm wardrobes then it would be cheaper and easier to buy 3 Ikea carcasses and hinges, build them up, box around them in with mdf and build your own doors from mdf.

Greensalad did something similar recently. 

paperclap

Doozergirl said:

If you've essentially got 3 x 1000mm wardrobes then it would be cheaper and easier to buy 3 Ikea carcasses and hinges, build them up, box around them in with mdf and build your own doors from mdf.

Greensalad did something similar recently. 

You could… but then you’ve got horrid shelf holes everywhere, and you either go for their short door height or tall door height. I’ll give it another look, but don’t think IKEA will completely work in our situation.

ThisIsWeird

paperclap said:

Thanks guys.

Sorry, let me clear up a few things.

For the carcasses, I’d planned to screw from the face of the left and right panels, into the end grain of the top and bottom panels. Funnily enough, I had thought of using pocket hole jig. I don’t have one, but was looking the other day, and do love trying new things! But thought “am I just making it more complicated than it needs to be?”. Would it be more beneficial? I’ve heard they’re super strong joins.

For the doors, I’d planned to screw the 12mm rails and 12mm stiles onto the 12mm panel… with wood glue. Detailing to be decided… but a v-groove is certainly a nice, understated feature. Biscuit joins could work nicely actually. Would certainly mean a lot less filling and sanding! But other than less filling, is there any other benefits?

On the MDF sagging issue… have heard that too. But, the largest span would be 1 metre… or maybe even just 50cm. Would a metre run the risk of sagging?

I had planned on using concealed hinges. Also called “Euro hinges” I think? But, the shaker style door will effectively be 24mm in places… and will be 24mm in the hinge area in particular. So hopefully not a problem 

To clarify, I was suggesting the biscuit joints for the main frame and not the doors. Dowels would probably do too.

For the doors I just used PVA for adding the Stiles, tho' you need to watch out for them moving (sliding) as you clamp them. Press down firmly and wiggle them about to ensure PVA is full coating, but excess squished out. Clamp (I just used spring-jawed plastic clamps). If you use screws, you'll not only have heads to fill (so send them in from the back) but also they raise the surface of the mating surfaces as they go through, which could lift and leave a tiny gap. Weights/clamps should do.

For the wardrobe carcase, consider whether the end panels, top panel and back are actually needed - could the existing walls and ceiling do? But understandable if you'd rather have it fully lined. 

ThisIsWeird

Yes, 1m is too large a span for an MDF shelf - 500mm should be fine.

And, yes, you'll have 24mm door thickness to play with.

Not sure what the best hinges to use are. They certainly need to be strong, have some adjustment, and 3-of for each door. That's the fun part...