MDF projects question

[master53yoda]

I'm working on some projects with my grand kids and I'm using MDF (for cost control) I'm finding an issue that I have never run ac cross using real wood. After making a shelf with them and making molding I find that the MDF has many pits etc because it pulls out the particles rather then cutting them as it does in wood and leaves a very rough surface that needs to be filled before sanding. Wood filler is to $$$$$ to use that much of it. is there something else that others have used. Below is a picture of the project we are working on right know my grand kids are from 7 to 11 and I have started working the 11 year old on the router table and table saw under very close supervision. the other 2 do sanding and cutting on the scroll saw and bandsaw (supervised of course)

[LarryG]

I can't tell the size of the piece in your first photo, but that doesn't look like MDF to me. That looks like particleboard.

Given reasonably sharp cutters, MDF machines quite nicely. At most a milled edge will feel slightly fuzzy as you run a finger over it. I don't thick I've ever experienced anything I'd call "tear-out" with MDF.

[Alex Franke]

yeah -- looks like particle board to me, too.

If it's edges you're trying to clean up, have you considered iron-on edge banding? It looks pretty good after it's trimmed to size, and it's very simple to "install".

[dbhost]

Another notice that that looks like particleboard and not MDF.

Particleboard is "Chunkier" than MDF and FAR more prone to tear out.

[docrowan]

MDF is pretty easy to seal the edges. I smooth it with a little with sandpaper, then run a bead of white glue down the edge. I run my finger down the edge to coat the glue all over, trying to work it into the MDF. I let the glue dry for several hours, then hit it again with 220 grit sandpaper. Seals the porous MDF and leaves a nice smooth edge, almost as smooth as the top.

If you are working with particle board, I have to agree with the others that you're going to have a hard time. Since you're painting it, how about drywall joint compound? Cheap and easy, sands pretty smooth. I haven't tried it myself but I've read about the technique several times.

[pelligrini]

I was thinking a plaster type filler too.

That doesn't look like MDF either. It appears to be a type of strand board, the wood chips are larger than most particleboard I've seen.

[Bill in Buena Park]

Perhaps this is OSB? Agree that the particles appear too large for MDF or particle board.

[master53yoda]

Maybe I'm calling wrong when I call it MDF it is the same stuff they make prefab counter top out of. the edges that I'm having trouble with have been formed with the molding bits I have for the router. the saw edges aren't bad because I use and 80 tooth blade in the BT3000 and a 60 tooth on my breakdown table. the router bits work fine on normal wood. I'm going to try using drywall compound as I can get it in a gallan bucket from Lowes cheap. I don't know why I never thought of sheet rock mud, I've used enough of it.

That piece in the first pic is a close up of 1 1/2" molding

[RodKirby]

THIS is MDF...

1/2" sides, 1/4" "shelf" - routs and cuts beautifully

[master53yoda]

from your picture what I'm using isn't MDF Lowes best particle board is what it is. I'd like to thank every one here for all the comments and info.

[Uncle Cracker]

What you appear to have is chipboard... I have sealed the edges before with fiberglass resin, and then sanded (ventilate the shop, wear a mask).

[Mr__Bill]

Assuming it's going to be painted, I second the joint compound idea. I have used it in the past and it works well. You do need to seal it, I used an exterior oil primer that I thinned down some. Primarily because that is what I had. Wallboard primer/sealer would work well too.

Have fun with the kids and don't forget the finished photo!

Bill

[cabinetman]

Particle board and chipboard are generic terms for a type of composite board. Their density can be varied by the size of the particle. OTOH, underlayment is a type of composite, the particles are much larger. The pictures posted could be a type of OSB, as it appears the size of the particles are much larger than ordinary particle board.

Edges can be sealed with glues, like white or yellow, or with several applications of waterbased polyurethane. In a jam, shellac could even be used. There are a few remedies for surface fixes, such as Durhams Rock Hard, spackle, drywall compound, wood putty, and Bondo.
.

[jking]

Particle board and chipboard are generic terms for a type of composite board. Their density can be varied by the size of the particle. OTOH, underlayment is a type of composite, the particles are much larger. The pictures posted could be a type of OSB, as it appears the size of the particles are much larger than ordinary particle board.

Edges can be sealed with glues, like white or yellow, or with several applications of waterbased polyurethane. In a jam, shellac could even be used. There are a few remedies for surface fixes, such as Durhams Rock Hard, spackle, drywall compound, wood putty, and Bondo.
.

I recall an article in one of the magazines a few years ago (Wood Mag, IIRC) that used particleboard for a project & sealed it with thinned down wood glue. I think they just used yellow wood glue thinned with water at a 1-to-1 ratio. I think it was a painted project, but, I don't remember for sure.