Best material to make a box behind a picture frame

[Lamentable]

I have a picture frame and I want to put a box behind it to house some electronics stuff.

The box dimensions would be slightly less than the frame in length and height. The depth I estimate will be around 150 - 200mm.

The final finish with be painted white, probably a water based paint as used on skirting boards.

The picture frame and stuff housed inside the box will be around 5 - 10kgs I'm guessing so the structure needs to support both the frame on the front and the electronics inside.

What would be the best material to make this from? Maybe a plywood? I feel ply is probably stronger than MDF but can it be painted as nicely?

How best to join the sides? Glue and a pocket hole jig?

I'm planning to attach the frame on the front in a similar way with glue and pocket hole screws.

Thanks in advance.

 

[RandomGrinch]

You're not Banksy, are you!!!???

 

[Deleted member 174758]

MDF will paint out far better than plywood, use 18mm thick. The corners will look better if you can manage a mitred corner as well. If you do use pocket holes you should be aware that they aren't ideal for either MDF or chipboard because those sheet materials are rather soft and can crack if the screws are over tightened. Personally I don't use them much, but the weight you want to support points to needing a box with a bit of bracing, thus:

where the internal bracing (to prevent sagging and give extra strength) coulde be made from MDF or 2 x 1 PAR softwood screwed and glued in place through the outside wall. The "lip" created at the front of the frame work could be used to fix to the back of the picture frame with screws. Ideally if a really smooth surface is required the outside of this box could be "wrapped" with four pieces of 3mm MDF glued in place

 

[Lamentable]

You're not Banksy, are you!!!???

Ha ha no I'm not. This project is for a "smart mirror". I intend to try and mount a 2nd hand PC monitor with the plastic bezel removed inside the box. This will be glued onto some hardboard which has been painted black. The whole assembly will then be pushed forward onto some 2 way mirror glass surrounded by a frame.

I got my inspiration from this project:

MDF will paint out far better than plywood, use 18mm thick. The corners will look better if you can manage a mitred corner as well. If you do use pocket holes you should be aware that they aren't ideal for either MDF or chipboard because those sheet materials are rather soft and can crack if the screws are over tightened. Personally I don't use them much, but the weight you want to support points to needing a box with a bit of bracing, thus:

I could try and do a mitred join. Ideally I wouldn't have any bracing as I would leave the entire front of the box without obstruction for the mirror glass to sit on. That's why I was thinking to use some harder wood and then join with screws and glue. Hopefully this would give some strength to the box. I was then planning to put some pieces across the back of the box behind the monitor to fix the monitor in place + give extra rigidity to the box.

Good idea to wrap the outside of the box with thin MDF. This is something potentially I could achieve. Could I mitre the edges on that as well given the width? I've got a mitre / chop saw.

 

[Deleted member 174758]

Good idea to wrap the outside of the box with thin MDF. This is something potentially I could achieve. Could I mitre the edges on that as well given the width? I've got a mitre / chop saw.

The thin MDF wrapping is a technique used in shop fitting. It means that you can build the main box from whatever you want for strength, e.g. plywood or softwood with butt joints and screws, dowels or biscuits to fix it together. Yes, it is possible to mitre thin stuff, although you may need to set-up a backet board of 18mm stuff on your mitre saw to support the thin material while you cut it. At only 3mm, though, it should be possible to butt joint and paint it in