Fixing MDF

Discussion in 'Carpenters' Talk' started by PlinkertyPlonk, Oct 9, 2018.

  1. PlinkertyPlonk

    PlinkertyPlonk New Member

    Hi, I'm thinking of making some adventure/play furniture for my kids out of mdf. i.e. a bed that looks like a castle.

    Just wondering if it's possible to screw mdf panels to a timber frame and then fill the screw holes so that they're completely invisible?

    Will wood filler shrink over time and be visible?
  2. chippie244

    chippie244 Well-Known Member

    Use 2 part filler, your kids will either wreck the stuff or grow out of it before it shrinks.
    kitfit1 likes this.
  3. kitfit1

    kitfit1 Well-Known Member

    Why not screw the frame to the MDF, then you won't have to fill the MDF at all.
  4. HarDeBloodyHarHar

    HarDeBloodyHarHar Active Member

    Be aware of the consequences of using MDF, the fibrous particles floating around your kids' bedroom.
  5. PlinkertyPlonk

    PlinkertyPlonk New Member

    Cheers. Does mdf absorb moisture like timber? I.e. even if the filler doesn’t shrink, will the mdf?
  6. PlinkertyPlonk

    PlinkertyPlonk New Member

    No problem, it’ll all be fully sealed with paint etc.
  7. PlinkertyPlonk

    PlinkertyPlonk New Member

    I did think of this, but if i screw into it from behind and use 18mm, or even 22mm mdf, will that be enough of a fixing? It doesn’t seem much to me?
  8. DIYDave.

    DIYDave. Well-Known Member

    MDF will absorb moisture way faster than real timber ...... think of a sponge :eek:

    Worse again than real timber, it will then swell and fall apart

    Guess your going to be painting the finished work ? so choose ur paint carefully and the moisture issue won’t be a problem

    Ever painted MDF before ?

    Read up on sealing the cut edges first, takes a little more work to get a good finish on cut edges

    The smooth faces are a joy to paint however - sounds like an interesting project :)
  9. kitfit1

    kitfit1 Well-Known Member

    For kids, i think it would be more than strong enough before they naturally destroy it anyway, just put more fixings in :D
  10. Richard_

    Richard_ Active Member

    Regarding dust, I presume you'll cut this outside then paint in a garage, then only a final assembly in the bedroom? Please please get a decent dust mask and change your clothes when you've finished or you'll be coughing for a week - the fibres can cause permenant damage to your lungs.

    This is my preferred type

    As for strength, a bead of glue with a screw from behind will be stronger than the MDF an no filling required.

    You could use a PU glue for extra strength, but be aware that any over spill that squeezes out the joint needs to be wiped off straight away.


    This stuff is the Rolls Royce...
  11. goldenboy

    goldenboy Well-Known Member

    Just a point on this.

    I use PU all the time.

    I always let and that squeezes out dry and whizz it off with a chisel. Not sure I would fancy trying to wipe it away.
  12. Richard_

    Richard_ Active Member

    Admittedly I've use it for structural stuff (box beams and glued decks) where aesthetics aren't important and we're dealing with hundreds of metres of glue lines. So a quick scrape with an offcut gets rid of any big blobs and runs, sometimes a second swipe in case it bubbles up after the first pass.

    We found it took longer to scrape off when dry, although that was on rough cut timber and OSB. Maybe it's easier to pop it off the surface of smoother timber? Or maybe it was the limitations of the chisel operator. :eek:
  13. sospan

    sospan Well-Known Member

    And of course keep it off your hands or wear gloves. PU glue turns your hands black and can't be washed off
  14. Jord86

    Jord86 Well-Known Member

    Three days is the average for it to wear off, learned through bitter experience. After doing a set of joists and flooring on a Friday, the amount of weekends on the lash/pull over the years where I've sheepishly handed a note over the bar between pinched finger and thumb and tried to receive the change as quick as I can without the attractive barmaid noticing my black and white minstrel hands I have honestly lost count. Nice clothes and a smile count for nothing it turns out when it appears you have gangrene at the end of your wrists.
  15. goldenboy

    goldenboy Well-Known Member

    I think its definitely the material rather than the user!

    PU glue is great stuff.

    Been doing lots of balustrade renovations recently. Stuff is a lifesaver!

    When doing the oak slips between spindles on a handrail/baserail I put a dob of pu in the middle of the slip to be fixed then a bead of mitrebond around the edge. Spray the baserail/handrail section with activator and then pop the slip in.

    The mitre bond goes off instant and clamps the slip and the pu gradually goes off giving the bond strength.

    Saves loads of time.
  16. goldenboy

    goldenboy Well-Known Member

    It does look horrid!
  17. sospan

    sospan Well-Known Member

    I have been using PU glue, Dulux primer which is blue/green, white undercoat and exterior mastic - I have had some odd looks at the tills. Some days I think there is more on me than goes on the material
  18. goldenboy

    goldenboy Well-Known Member

    Is that the Dulux Weathershield stuff?
  19. goldenboy

    goldenboy Well-Known Member

    I once was machining up a load of really soft softwood so big fluffy shavings.

    I had a sort of softshell top on with a fleece back to it.

    The shavings slipped off the front of it but stuck to the back like a magnet.

    I ended up looking like the Gruffalo.
  20. Richard_

    Richard_ Active Member

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