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mdf/particle to wood edge glue bond strength?4/24
I am building a solid "soundproof" door consisting of multiple layers of 3/4 mdf and 1/2 plywood sandwiching greenglue between. To be able to mount it, and to protect the edges, I plan on framing the outside edges in 1/2" poplar. My concern is with the weight and the glue bond strength. The door will end up about 2 1/2" to 3"thick and will be hung on 3 ball bearing hinges with 4 long screws each.
Which glue should I use and what issues should I expect? Any suggested tips?
If your saying your going to be mounting the door to the 1/2" poplar and possibly mdf behind it....I wouldn't do it. MDF is about the worst material out there for screw holding.
Instead one method I might try would be to route a nice deep slot into the edge of the core of the door once it's built. Then you can insert your solid wood edge into this. I'm thinking the solid wood being a T shape extending into the door several inches. This will give you a much greater joint to support the weight of that door.
I'm sure others will follow with more suggestions as well. There have got to be plenty of ways to do this, but I would not trust what I think your describing.
Just to clarify. My intention is to laminate mdf and plywood to about 2.5 - 3 inches thick using screws and Green Glue sound proofing material. This will then have the outside edges glued to poplar boards, probably 1/2" thick. I've made worktables this way before (laminated mdf with wood edges), but I've never hung a door made this way.
The poplar is to give some protection to the edges and to give some real material to mount the hinges on. However, I am concerned about the joint between the poplar and the mdf.
Right, so when you mount the hinges what are the screws grabbing to hold up that heavy door? It sounds like your thinking the poplar is going to do it? The glue joint is just one problem, 1/2" poplar isn't anywhere near enough material for that kind of holding power. Even if the glue joint did hold up, (which for the other edges it should), carrying the weight of a 2-1/2"+ thick door....no way!
So behind that 1/2" poplar the screws are going into maybe plywood, maybe mdf, maybe the seam between two layers? You don't give us the size but lets say it's 30" x 84" x 2-1/2" thick made out of mdf and plywood. That door is likely well over 100 lbs at that size. Now your fastening your hinges to where there's the least amount of screw holding power!
This issue IMHO is much more important than the glue joint,....which should be fine for the other edges as long as you have a good clean edge to glue to. That's why I suggested inserting the solid wood into your sandwich, this will provide the "meat" to hold the screws.
I think where JeffD is going about the MDF/Ply holding the long screws is that there isn't a worse material choice for screw hold ability. The glue line for the 1/2" edge, if done well won't fail. But there isn't enough wood to hold the wt. I like Jeff's idea of a T member imbedded. By going to the T shape you get face of panel to long grain of wood bond, far better than edge of ply or MDF.
JeffD is spot on in his remarks.
The simpler solution is to use 1" poplar as your framing. This will provide sufficient material for the hinge screws. Poplar is cheap and it may help to keep the door straight/flat.
Titebond 1 or any PVA will work fine as an adhesive.
You haven't mentioned your layup schedule. It is best to have odd layers in laminates. It balances the panel and helps to prevent massive warping. Basically mdf/ply/mdf or mdf/ply/mdf/ply/mdf. 3 or 5 layers.