I was trying to make a box this weekend. I couldn't get the 3/4" MDF to stop splitting when I screwed it together. I didn't have this problem before, but this time I bought the wood from Home Depot as opposed to a lumber yard. Do you think that the wood is of lesser quality or something? I pre drilled the holes.

What some of these places call mdf is actually waferboard. You should shop around more and find some mdf that is denser

maybe you didn't drill the pilot holes big enough...

Are you using the same screws? If not maybe the threds are too coarse or vice-versa.

Here is an Idea. . . . . . .Fing a better glue and don't screw it together! Your box will be stronger and you won't have to deal with this problem. If you don't like that idea, you could also use a different wood. It will be easier to work with, lighter, and more forgiving to the elements but it will be expensive and hard to find if don't know where to look.

I used different types of screws on scrap pieces, and every one of them split it. I use liquid nails and screws. I never thought of just using glue. Ya think it will hold under all that pressure?

I'll try to make bigger pilot holes to see if it helps.

Jachin - I'm thinking you may be on to something here. When I take a close look at this wood, it seems to have layers in it like a Kit Kat bar. I think the other MDF I got was pretty solid.

Make sure you drill a countersink as well. Typically it'* not the screw threads that split a board, it'* the head.

I wouldn't use just glue unless you have lots of bar clamps and put dadoes and rabbits to increase the gluing surface.

glue doesnt work maybe for sealing but not anything else

Then I guess everyone of my boxes doesn't work.

I've built 3 boxes for my old 15w3'* - all without screws. If the box can handle 2 -15 with 1000 watts then I think it works. I've built a box for my 10w7 and it is still completly sealed (hasn't blown apart) - no screws. I've built a box for a 18w3 in a *-10 - without screws. That setup has actually cracked his windshield and sucked and blown his roof in and out so bad that it is now dented in for good. If it can handle that kind of pressure then I think that it works.

I know it sounds crazy to do this - I was doubtful the first time too but don't say it will not work when no one has done it. I wouldn't even think to using crappy liquid nail or just normal wood glue to do this. You need a polyurethane glue that is actually going to laminate the two surfaces together. Yes you will need to have bar clamps or lots of weight to do this. Yes putting dadoes and rabbits will increase the gluing surface thus increasing the strength of the joint but this is not needed since it is greatly stronger then a joint with screws. Screws will actually weeken the joint in a MDF appiclation.

Yeah you can glue if you got some real nice stuff, make sure it cures 100% before you blast away with the watts... But drilling pilot holes is key to not splitting anything.

I did drill the holes. So I guess what'* left to ask is - What types of screws, and what size hole do I drill. In relation to the screw do I drill a 80% sized hole?

I'll play around tonight.