Filling countersunk screw holes in MDF

[JamieB3009]

Hello,

I have installed MDF skirtings and architraves to a room and have fixed these using countersunk screws in places where the walls arent straight and adhesive isnt covering it. I have used ronseal 2 part wood filler to fill the holes and sanded back. When i came back to the holes a couple of days later they felt slightly proud around the edge of the fill compared to the rest of the frame. Is this normal and will this keep happening if i sand again? I dug one of the holes out and the filler definitely seemed to have taken as it was very hard to remove. Is this filler the best to use for MDF?

Thanks,

 

[Wayners]

If you use that 2 packs wood filler to fill holes, do it in two hits letting first set.
Also smooth off well and keep the filler off wood surfaces as much as you can. You need to keep sanding to a minimum so fill it tidy. Take your time.
it's tempting to fill proud with blobs of filler, but don't.
Glue sandpaper to blocks of wood so you keep surface flat when sanding.

120 grade and 180 grade sandpaper

 

[shd1970]

Sorry for hijacking this old thread but I’ve the same job to do myself

@Wayners - do I need to seal or do anything to the screw head to ensure the filler sticks please ?

 

[freddiemercurystwin]

No just dust free, I rarely manage to fill anything in timber with just one round of filler. I've used Toupret wood repair filler for this kind of thing which set quite hard

 

[shd1970]

No just dust free, I rarely manage to fill anything in timber with just one round of filler. I've used Toupret wood repair filler for this kind of thing which set quite hard

Thanks @freddiemercurystwin
What about painting afterwards?
Usual approach of primer, undercoat and topcoat or have you found you need to do something else for the filler?

 

[freddiemercurystwin]

Just prime and paint etc as you would the MDF.

 

[opps]

It might be the case that the MDF has contracted very slightly as it reaches the relative humidity of the room. I used to specialise in hand painting MDF units. The cabinet makers would never have visible screw holes that needed to be filled for that very reason. With skirtings, as you have said, sometimes, using a screw is unavoidable.

In most cases, once the MDF has shrunk back, the filler resanded, and MDF painted, it, the filler tends to behave.

 

[foxhole]

Or foam fix, no screws required.

 

[Wayners]

If you're using 2 pack wood filler over screws it really sticks and is waterproof.

If using powdered filler mixed with water I used to undercoat MDF and screws first.

Problem with 2 pack wood filler it's hard to sand smooth. You have to fill in 2 goes and be tidy. Then you have an easier time sanding

 

[Mottie]

Just prime and paint etc as you would the MDF.

3/10

 

[opps]

3/10

???

There was nothing wrong with @freddiemercurystwin 's reply.

As a decorator, like @freddiemercurystwin and @Wayners , I often do a double fill when trying to minimise sanding. It is incredibly difficult to flush fill a hole with hard fillers, in part because there is air which needs to be expelled when you pull your filling knife over the surface.

 

[Mottie]

???

There was nothing wrong with @freddiemercurystwin 's reply.

As a decorator, like @freddiemercurystwin and @Wayners , I often do a double fill when trying to minimise sanding. It is incredibly difficult to flush fill a hole with hard fillers, in part because there is air which needs to be expelled when you pull your filling knife over the surface.

And there’s fúck all wrong with my breakfast thread but if the tw@t insists on trolling me in that thread, as I said, I’ll troll him back.

 

[GhostIntMachine]

@shd1970 just be aware that 2-pack filler is so hard that it normally needs to be machine sanded - pretty difficult to sand it out adequatelyby hand

 

[opps]

@shd1970 just be aware that 2-pack filler is so hard that it normally needs to be machine sanded - pretty difficult to sand it out adequatelyby hand

I am lucky enough to have loads of nice festool sanders, however I do have to sand two pack by hand occasionally. With a sanding block, it isn't too much of a hardship. 80 0r 100 grit and a cork block.

 

[GhostIntMachine]

@opps it all depends on how much you have got to do. I always find that decorators bitch about the amount of work it take to hand sand 2-pack. They want the joiners to sand it out for them uf possible