Attaching a top to a unit?!?!?!

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Iestynd

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Hi all,

I'm after some advice from you very experienced people. I have been making some bedside tables out of MDF. They are going to be fixed to the wall (floating) as thats what my wife has asked me to make.

WhatsApp Image 2023-06-20 at 17.11.21.jpeg


Its all going to get 2 coats of MDF primer/sealer and then a top coat, with the drawer done in a contrasting colour. The pin holes have since been filled with "car bodge" as it doesn't shrink and sands incredibly well. Thats all fine. So the top, at the moment i placed a bit of scrap MDF to show how the top might look but i'm waiting to source some oak furniture boards... at this rate i may end up buying the oak boards and joining them myself but i'd rather not. The lead times/prices on pre assembled boards of 20 - 30 mm thickness is crazy.

The question i have though is, when i come to attach the oak tops (after painting) will glueing them on be sufficient? The dimensions of the oak will be cira 450mm x 350mm (give or take). I had though i could domino them, but thats going to take some expert measuring as the tops are going to overhang so the alignment won't be the same reference point... not impossible but it did get me wondering what benefit would that give me? A beech domino 20mm into the MDF and 10MM into the OAK?
Tightbond 2 on its own, properly clamped and allowed to dry should be ok or not?

What would you do?

Thank you
 
You cannot glue or joint a solid oak top to the unit. It will want to expand and contract, pulling itself apart or cupping.
Ideally you want slotted holes in the mdf for fixing the oak top to allow for movement. You can get away with this if you drill a couple of 6mm diameter holes along the front edge and a couple more along the back edge of the mdf top, about 25/30mm in from the edge. Fix through these with a large headed washer and a raised/domed/round head screw of 3.5mm gauge. Do not use steel, but stainless steel. Brass is also good but the heads are easy to snap off. Whichever you choose make sure you pilot drill the oak first and run a steel scre in and out to cut a thread. Do not over tighten the final fixing screws.

Colin
 
Thanks for the replies so far. I think what your saying is to fit an MDF top and then screw threw this into the oak? I wasn't planning on having an MDF top at all. I thought the oak would just clue to the end grain of the MDF (3 sides as its open on the front).
Maybe a veneered oak top would be better as its more stable?

Thank You
 
Just had another thought... I could, if i was good enough route a 18mm channel in the underside of the oak top and that way the MDF would sitinto it a bit, i could then get a LOT of glue covered to hopefully stop the oak top cupping and moving?

Thank You
 
bingo a veneered oak top is the best 4 l brackets from inside your done. you will need some solid for the edges( glue and domis or brads depending on your bosses fussiness!) mitre or butt at the corners.
 
Can I ask why you are considering solid oak if it's going to be painted ?. MDF will actually look better if painted. There are a few options for attaching the top with an overhang and probably the easiest is to use 8mm dowels. Drill the holes for the dowels and use some cheap dowel locator/finders to mark the bottom edge ,insert dowels and tap home. Easy as .
 
I'm not sure i've explained the design properly. The oak is going to stay oak, to match a desk within that room and some shelves.

WhatsApp Image 2023-06-21 at 15.36.25.jpeg


Sort of like that....


This kind of style:
1687358449047.png




Thanks again.
 
Just had another thought... I could, if i was good enough route a 18mm channel in the underside of the oak top and that way the MDF would sitinto it a bit, i could then get a LOT of glue covered to hopefully stop the oak top cupping and moving?

Thank You
Still a definite no to glue. I'm assuming you plan to have the grain running side to side of the unit. If it were me I would complete the mdf carcass with a top so you have a more solid construction and screw the oak top using slotted holes in the MDF.
But going with your plan, you say the units will attached to the wall so the top just needs locating i.e. it doesn't have to have a strong enough connection to enable you to lift the unit by the top. You could use table top expansion brackets such as these which would hold the oak top in place nicely and allow for movement e.g. https://www.amazon.com/Expansion-Fastener-Connector-Woodwork-Woodworking/dp/B08BH43XWX.

Just make sure that you orient the brackets so that the slot is going across the grain of the oak
 
Fair enough. If the top is solid wood I would suggest using four metal tabletop fasteners from underneath
Some are designed with a slotted hole to allow movement and others are cranked to fit in a small slot in the sidewall of the unit.
 
Some small angle brackets 25 x25 mm as used by kitchen fitters should do the job.
 
I would either add an MDF top inside your sides then screw the oak to to it with slotted holes, or use slotted brackets / buttons as suggested above and add an apron across the top of the opening to support/hide the fixings.
 
Thanks all.

Understood. The cranked table top brackets look ideal. If i'd have thought about the buttons before assembly I would have been about to route some slots into the MDF sides. Although typing this, i guess i still could of i had a decent enough base for the router to sit on.

Thank You
 
You could also fix the table top at the back edges (fixed with glue and a single domino) which would then allow it to expand or contract forwards only. If you do allow movement in all directions it might end with an unsightly gap at the back edge, whereas the overhang at the front changing is rather irrelevant and hard to read.

You wouldn’t need to re set the domino, you can figure out a packer (without thinking it through something that’s exactly the overhang ?)
 
This method is also good because you can then use some kind of bracket or whatever at the top back to fix it to the wall.

Incidentally the image you chose shows “breadboard ends” which are a good option, although I probably wouldn’t bother on a top so small unless I required that look, but well worth reading up on them. Quite easy to do with a domino with one fixed at the back, then some sloppy holes for the rest.
You can then fix the breadboards down very firmly to the mdf carcasse (so long as you avoid your breadboard dominos)
 

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