Gluing Steel to MDF
If the steel is somehow stress-relieved or textured, it will help. If the steel has oil-canning and a glossy finish, it will never look good. Oil-canning could possibly show up later after the temperature has normalized.
The smaller the piece of steel, the less problem you'll have. 1/8" thickness seems like overkill, as it (the steel) will be many, many times more durable than the substrate. I'm curious as to why 1/8" was spec'd, and not - say - 24 ga? 1/8" will be very heavy, and will have a lot of minute defects and scratches that will only show up after it's painted - ask any auto-body man.
From the original questioner:
Thanks. The defects are part of the design, and will remain. My main concern is warp, as there is no balance sheet on the other side of the mdf (just finish).
From contributor D:
Better have some good hinges.
From contributor A:
Architects are always good for a chuckle. Get him, contractor, and customer to sign a warranty waiver for this project.
We are in boat builder country and they have being using Plexus Adhesive extensively for the last decade. It has replaced the use of 3M 5200 poly for deck/hull bonding. It is also used, as noted by its description, for bonding almost anything. They use it to glue the mainsail aluminum track to carbon fiber masts with no mechanical fasteners. I'm talking Americas Cup yachts. It's got around a 20k psi shear strength (epoxy is about 6k). Smells like melting plexiglass. It is the high strength distant cousin of solid surface glue.
I would use this instead of typical construction adhesive or a poly glue. I would actually choose 3M 5200 over those as well. Jamestown Distributor's tech department is excellent. I would give them a call for their opinion.
From contributor S:
Well, I can't imagine that any of the steel panels are going to warp very much if you start with flat sheets. What is the largest panel size?
Looks like mild steel weighs 5.1 lbs per sq foot at .125" thickness. And if you are going to be machining any part of this, keep in mind that domestic steel will likely be more easily worked than imported. In my experience, imported steel can have a lot of variation as far as thickness, hardness, etc. One area will be as soft as aluminum, while another area will be as hard as a drill bit - all on the same sheet!
Steel that is put up inconsistently like that can act like a piece of lumber - nice and straight until you rip it, then it goes crazy. I'd suggest you check with a good welding shop and get their input. I love these off-the-wall ideas people come up with and I hope you can someday post pictures of this project.
Good luck, bid it to make money, and have fun.
From contributor K:
I used Simpson SET High Strength Epoxy-Tie to insert some steel strap into some ply for a cantilevered sub deck. Worked great. Depending on how many you have to do, they have self mixing cartridges. You could shoot out a bead, then hit it with a small notched thin set trowel.
From contributor M:
I agree that 1/8 is way too thick for this application. All your hinges will sag and most likely pull out of the soft MDF. You have to get it under 1/16".
Are you using a fastened door pull that will add to holding strength?
If you get it under 1/16, I've used commercial grade contact adhesive to bond sheet metal to MDF before. As for expanding, I don't believe you will have enough temperature change to alter the metal.
I'd go with Chem Metal. Make sure you add on enough for all this extra time and frustration.
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