Best way to face glue MDF?

[Jay Yoder]

I need to put (3) ¾” x 17-1/2” x 62-1/2” pieces of MDF together face-to-face to make a top. I have thought of a few different methods for this. I could either use yellow glue between each layer or I could use contact cement. The advantage of the contact cement would be that once down, it would not slide around like the yellow glue would. Once the pieces are together, I would use a J-roller to roll them together. Has anyone else done this? I was planning on cutting the first (bottom) layer to finished size and then adding the next layer which is cut slightly oversized. Once the glue dries I would use a flush trimmer in the router to match it to the first. The procedure for the 3rd (top) layer would be same as the 2nd. Any comments on this?

[Dustin Lorenz]

Use the contact Cement. I've used it for quite a few bench tops and it works great, just remember to be well ventilated as the fumes are very strong. If you have never used it search for a how to and it should describe how to apply and check for setup and how to use "sticks" of scrap to keep the pieces seperated while lineing every thing up and also reapplying if you take to long to get back to it. Don't be intimidated just be patient, because once you touch those coated surface together that is it and it will go down that way.

[Mike Henderson]

When I had to do something similar with MDF, I found a section of concrete floor that was flat (checked it with a long straight edge). Then I put PVA glue on the two pieces, spread with a roller. Laid one on the flat surface (glue up) and then put the other on top. Then piled everything heavy I could find on top of it. Glued up fine.

The problem I see is to make sure the stack is flat while being glued. By the time you get to three layers, the bend will be permanent.

Mike

[Chuck Isaacson]

I just did two layers if MDF for my router table top. I used Titebond and had no problems what so ever. There is definitely a bond there. I also used some 1 1/4" screws. This also help for the clamping aspect. I just made sure that what I was gluing it up on was flat. Another things that I would do differently is to make sure that I roll out the glue to make sure that I have a nice even surface. I just kind of drizzled it on there and then laid the other sheet on there. One more thing, what is this top going to be used for? Why are you using three layers? That to me seems a little overkill. Just curious. I am sure that you have a plan..

CHuck

[Larry Fox]

Know anyone with a vacuum veneer press and a big bag? When I did it for my bench I used yellow glue and screwed the layers together where I knew there would be no dog holes or hardware. Been holding up very well for years.

[glenn bradley]

I was planning on cutting the first (bottom) layer to finished size and then adding the next layer which is cut slightly oversized. Once the glue dries I would use a flush trimmer in the router to match it to the first. The procedure for the 3rd (top) layer would be same as the 2nd. Any comments on this?

This is how I did my four 3/4" MDF layer 30" x 88" workbench top. I used a plastic scraper (bondo paddle?) to spread the Titebond II. To avoid the slipping around and aid in 'center of panel' clamping, I pre-drilled and threaded in screws. I removed the screws, applied the glue and then used the screws to re-align the panels. This was an upside down assembly with the eventual top surface facing down throughout the process. Between cauls, weights and the screws I was able to get a good even pressure. I used my TS top (with 4 extension wings) as a known flat work surface.

I trimmed the oversize panel with a flushtrim bit as described and repeated the procedure till I had all four layers complete. I mapped where I would leave the screws in place so I could mount my vises and drill dog holes and all that without encountering any screws. If you used a good quality screws, you could just back them all out. I used drywall screws which would mostly snap off when I tried to back them out of my test pieces.

[Chris Tsutsui]

One easy way is to use yellow glue, pin nails to prevent it from sliding, then clamp.

If I wanted it absolutely perfect I would yellow glue oversize panels together with clamps only. Then trim it to final dimensions with table saw or track saw, etc.

[Prashun Patel]

I used yellow glue.

Cut the middle piece to the proper size. Then cut the two outside pieces oversized by 1/16". Even if the outsides slide, just make sure they're proud of the center piece which'll serve as a template for a flush trimming bit.

To clamp, just drive screws in from the piece that'll be the underside.

I think contact cement'll be too much trouble. It works well for larger, thinner veneers that will bend. In that case, you line up the two mating faces separated only by thin ripped strips of wood. When you remove the strips one by one, the faces bend together and make even contact. With your smaller, thicker pieces, you won't get enough flex to let it lay down nice.

[Josiah Bartlett]

The old style glazier's points (the diamond shaped ones) work pretty well to keep the panels from creeping while gluing if you can't use screws.

[Myk Rian]

I use two 3/4" pieces to make my router tables. Often you will find that MDF is slightly concave. Put the convex sides together to make the whole panel flat. Like this: )(

[Mike Heidrick]

Stack the first and second layers, clamp, pre drill with counter sink for 1 1/4" screws, un clamp, open up, spread glue evenly, re stack, clamp, drive screws, remove clamps, clean up any squeeze out, stack third sheet, clamp, pre drill with counter sink, un clamp, open up, spread glue evenly, re stack, clamp, drive screws, un clamp, clean up any additional squeeze out - done.

Now you are ready to laminate.

[Jay Yoder]

This top if for the top of my midi lathe stand, that is why it is 3 layers. I have a Jet 1220 w/extenssion. I thought about using the 1-1/4 screws, but decided against it b/c i did not want to leave them in. I thought abt doing the oversize method and cutting it on tablesaw, but thought that might be kinda bulky to maneuver, but that would be the easiest. Not to mention woudl leave less of a mess! Maybe another option would be the combination of contact cement and table saw trimming. How long does contact cement need to cure? Now that I think of it, would my freud fusion blade be good for cutting this assembly?

[Chuck Isaacson]

I think that the easiest, cleanest, best way to do this is with the table saw. Cut the pieces 1" over sized and then trim it down when it is all glued up. That is an awful lot of MDF dust if you do it with a router. It will be heavy to move around but still I think the best way.

Chuck

[Tom Veatch]

I ... Any comments on this?

Personally, I like contact cement for that type of application. Recently the guys at my local lumber store gave me a can of solvent based gel type to evaluate - they were trying to decide whether to stock it or not. I found it spread to an even coat easier, actually seemed to be a little forgiving on placement, and the solvent seemed to be a little less overpowering.

Be aware that the cement soaks into the mdf, so you'd likely need a couple of coats to get a reliable bond.

One sheet slightly oversized and flush trimmed with a router is my standard way of getting laminated pieces trimed to size. With mdf, however, the central part of the edge where the flush trim bearing rides is not the hardest, sturdiest material in the world, so you'd need to be a little gentle running the router around the edge during the trim operation.

All in all, I've had good success with router trimming laminated mdf bonded with solvent based contact cement. You do need good ventilation as the solvent vapors are explosively flammable (never had a problem with that) and can give you a really cheap drunk (have felt a little woozy when there wasn't adequate cross ventilation).

[Jerome Hanby]

I think Jay is working on the same project I am . I used Titebond, just squirted it on out of the bottle and used my biggest acid brush to spread it around. If I were doing it again, I'd build some type of jig or drill holes for dowels to make sure all the edges stayed perfectly even. Mine were a bit uneven, and I had problems getting everything square and even. Longest trim router bit I had wasn't quite long enough. To add to the fun, it wasn't always the outside layer that was the "shortest" piece. I ended up using my largest pattern bit with a straight edge to guide it to square the "top" on one side, then flipping the piece over and using the long trim bit to even the rest to that first "square" pass. One router, so I had to change bits for each operation, and I was feeling my way along, so I only did one side at a time, so about eight bit changes and piece flips to get a nice square, smooth piece. Eight three inch long dowels and a flush cut saw could have saved a lot of work and a ton of MDF dust. Could probably counter sink some holes and use screws to pull everything together layer 1 to layer 2, then again with layer 2 to layer 3, but would have to keep track of them when the top gets drilled for mounting holes. If you did two glue ups, I guess you could remove the screws after the first two layers dry and repeat to add the third layer.