Question - bonding MDF to painted surface

[Dave Jenkens]

Hello group,

New to the group (mostly lurking and learning), relatively new to woodworking.

I was given a set of drawers made of MDF and finished with latex paint (semi-gloss). I built a cabinet for them and am using them for shop storage.

The bottoms of the drawers are made of 1/8 inch hardboard, but unfortunately, are simply nailed to the botom of the drawers, rather than being set into dadoes. I find the drawers won't take very much weight before the botoms sag, which causes the drawer below to "hang up" on the one above as I try to open them.

To remedy this and improve the weight carrying ability, I thought of removing the botoms and gluing rectangular strips (1/2 x 3/4), to the inside perimeter of the drawers and then droping in a 1/4" or 3/8" plywood bottom onto the strips.

I wanted to know if anyone can suggest a glue that will bond MDF (or other wood material), to latex paint, as I don't want to have to sand down all the drawer boxes.

Perhaps some also has an alternative way to "fix" these drawers ?

If it were just a few drawers, I would simply scrap these and build new ones with a better design, but there are 14 of them and I have several other more pressing projects I'd like to be working on.

Thank you in advance to anyone who can offer some suggestions.

Dave J.

[Robatoy]

I have one of those cheapo rabbeting bits with a multitude of bearing sizes, right down to 1/16". If you were to run that along the inside perimeter of the drawer box (bottom), it would remove the paint and give your cleats a nice toothy surface to adhere to. So what if you can't get quite into the corner..just make the cleat a bit shorter.

[Andy]

Welcome to the group. I think your idea of supports inside the drawers is a good one - at least a lot better than the current drawer design. As far as gluing to MDF or latex paint, I've had good luck with Gorilla Glue (or similar polyurethane glue). You will probably want to rough up both surfaces with coarse sandpaper or a rasp first, dust them off, and make sure they're at least a little bit moist, then use gorilla glue and clamps. Far easier than sanding to bare wood, though. Be aware that this glue foams, so you'll probably get some foamy squeeze-out that hardens, but it's fairly easy to scrape off. Good luck, Andy

[Saudade]

How about using a slot cutting bit in a router to make some dadoes in the side and front of the drawer. You could trim off the bottom of the drawer back to slide the plywood into the slot. Since the dadoes won't meet properly at the front corners, you could simply trim the front corners of the plywood bottom to fit. You could clamp a 2x4 (or something) along the side to give you a broader base for the router to ride on.

[Bob S]

Welcome Dave,

I think if you just do a bit of sanding where the strips will be mounted and use regular yellow glue they will be fine for light loads. The latex has most likely soaked in real well to the MDF and the glue should have no problem adhering to the sanded sections.

To make the strips stronger add 3 screws thru the MDF and into the strips. Drill thru the MDF (use same size bit as the major diameter of screw) and countersink the heads. Use plain old pine for the strips unless you have some scrap hardwood lying around that you can cut into strips. Glue the strips to the drawers, add the screws and then secure the drop-in bottoms with small brads or glue.

Bob S.

[dadiOH]

Use caulk. Cheapo "painter's" latex type would be fine. If you don't completely trust it (I would) add a couple of small screws or brads.

The strips below the bottoms won't keep them from sagging though...to do that, add strips *above* the bottoms too. Strips 3/8 x 3/8 or 1/4 x

1/4 above and below would fix them fine.

Alternatively, glue the drawer bottoms to all drawer vertical parts. The strips are better.

-- dadiOH ____________________________

dadiOH's dandies v3.06... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at

[Dave Jenkens]

Thank you for your reply to my inquiry. The latex caulking sounds like an interesting idea. I didn't mention in my original post - I aboslutel intended to use brads or screws to hold the strips, in addition to whatever glue.

SNIP

As to the sagging, I may not have clearly explained my intent. I know the sagging cannot be prevented because the existing bottoms are just too thin. My intent was to REMOVE the existing material and go to 1/4 or 3/8 plywood, which would not sag.

Thanks again for your ideas

Dave J.

[Dave Jenkens]

Hello Bob,

Thank you.

OK - I'll perhaps try that on one drawer to see how it works.

Didn't put it in my original post, but was going to use brads or screws.

Thanks for that tip. I have done that previously when joining materials.

Have a related tip I would like to share. After driiling and countersinking the piece the screw will pass right through, flip it over and slightly countersink the hole where the screw will come out of. This area allows a space for wood particles that lift up out of the blind hole that the screw goes into in the other board and allows a super tight fit between the two boards. Especially good when screwing into particle board or MDF. Not my original idea - I saw it in a book of tips and am just passing it on.

Dave J.

[Dave Jenkens]

Great idea, Saudade. I don't have a slot cutted bit, but I can possible borrow one.

thank you for the idea,

Dave J.

>

[Dave Jenkens]

Hello Andy,

thank you.

SNIP

I have ELMER's band Pro Bond polyurethane, which is probably similar.

SNIP

Thank you for that tip. I have worked with polyurethane previously doing some boat repairs and discovere the foaming.

Dave J.

[Dave Jenkens]

Very good suggestion - thank you !

Dave J.

[dadiOH]

Depends on what you put in the drawers. :)

For a bottom to sag it has to *bend*. A tight fit twixt top and bottom strips plus glue helps keep it from bending.

-- dadiOH ____________________________

dadiOH's dandies v3.06... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at

[Bob S]

Good tip - thanks,

Bob S.