Thread: Coffee Table Top Expansion

Probably yes; when the panel expands it can destroy your mitres.

If you want to keep the design an alternative would be to lay oak veneer on a panel made from plywood or MDF as they are stable substrates.

Originally Posted by Chief Tiff

Probably yes; when the panel expands it can destroy your mitres.

If you want to keep the design an alternative would be to lay oak veneer on a panel made from plywood or MDF as they are stable substrates.

Thanks for the reply, I was just checking because its only 560mm wide...

What if it was butt joints?

Butt joints will also shear. If you try to contain the expansion with mortise & tenon joints the resulting internal stresses can warp the panel or burst the mortises.

You can use breadboard ends but that removes the long edges and you’d need to increase the width of the panel to compensate. Probably the best alternative though if you don’t want to use a veneered panel.

There is no easy way to achieve inserting a solid wood panel into a frame without leaving gaps for expansion. Using quarter sawn timber for the frame and backsawn timber for the panel can only reduce the amount of expansion but backsawn timbers are usually boring to look at; if you’re using real oak (not one of the Aussie eucalypts like “Tassie Oak”) not using quarter sawn timber means you don’t see the medullary rays oak is famous for.

You can try and build it as per your original design but all it takes is a couple of really humid days and you’re burgered.

Thanks Chief, I'll use oak veneered ply just to be on the safe side.

An option would be to design a small expressed joint in between the insert and the perimeter frame
It can still look nice and will accommodate any movement

As CT says. Even if you have zero movement in the panel, you will still have movement in the frame and this will create tension.

A common solution is to locate the panel in a groove in the frame. Just a small drop of glue in the middle of each groove and the panel is free to expand and contract in its slot. Something like this.

Panel.jpg Expanded View

Originally Posted by GraemeCook

As CT says. Even if you have zero movement in the panel, you will still have movement in the frame and this will create tension.

A common solution is to locate the panel in a groove in the frame. Just a small drop of glue in the middle of each groove and the panel is free to expand and contract in its slot. Something like this.

Thanks for the reply Graeme. That's how I normally do it however the coffee table top is part of something much larger whereby one side has to be completely flat, see build thread:

A Coffee Table With A Twist

Construction has already started but haven't had time to upload my progress to the thread yet.

In a previous life I built an entertainment unit for my son. This was before people here attended to my education and taught me about wood movement issues.

The top of the 1,500 mm X 450 mm cabinet is solid timber with a 50 mm frame. Exactly what we should not do.

That was about 7 or 8 years ago. The cabinet survives ... but don't ask me for how long.

One thing in my favour is that the timber, NG Rosewood, is a low movement timber.

If you really want a frame around it I'd recommend 2mm shop cut veneers over MDF or particleboard.

Originally Posted by John Samuel

In a previous life I built an entertainment unit for my son. This was before people here attended to my education and taught me about wood movement issues.

The top of the 1,500 mm X 450 mm cabinet is solid timber with a 50 mm frame. Exactly what we should not do.

That was about 7 or 8 years ago. The cabinet survives ... but don't ask me for how long.

One thing in my favour is that the timber, NG Rosewood, is a low movement timber.

If you really want a frame around it I'd recommend 2mm shop cut veneers over MDF or particleboard.

Hi John, I've ordered some Veneered birch plywood, I've not had any trouble with the stuff, so I'm happy to go with that. From my limited understanding (from reading / watching projects being built), wood movement only becomes an issue over a certain width?. Frame and panel doors on kitchen doors etc is so minimal its on a quantum scale, this is why I wanted peoples opinions on if 560mm wide would be an issue.

Originally Posted by EagerBeaver71

Hi John, I've ordered some Veneered birch plywood, I've not had any trouble with the stuff, so I'm happy to go with that. From my limited understanding (from reading / watching projects being built), wood movement only becomes an issue over a certain width?. Frame and panel doors on kitchen doors etc is so minimal its on a quantum scale, this is why I wanted peoples opinions on if 560mm wide would be an issue.

Frame and panel doors, use a floating panel. That’s why movement is not an issue with them.
All boards expand and contract, for example, a 200mm wide board might only move 1mm, but a 600mm wide board of the same species would likely move 3mm. You would need to research the rate of movement for your particular wood type

Originally Posted by EagerBeaver71

Will I have any issue with expansion gluing a 560mm wide oak board into a rabbet frame like this:

grain.jpg

If you use solid wood and just glue the frame around it like that, yes movement will show up pretty quick .
It can be done from solid and last well but the joinery has to be more involved than that above . And it only lasts as well as the piece is kept in a good environment. I do wide table tops the same as above . Ive done them for roughly 20 years that way and only one came back for repair . It was locked away in storage by the clients and the room flooded and wasn't discovered for a while. The strong joinery holding the mitre together on that one was smashed open . And they paid for the repair job. You either have to lock the mitres with the dovetailed W Patch on the under side or you loose tenon then glue and peg it . Then seal both sides of the top when finishing .

Or like has been said you do it by veneering the center panel on manufactured board . Good plywood is the best. And it wont give you any trouble unless like the solid job its left in a bad environment. Its unlikely to show at the joints but veneer can lift off. I do them like that as well but use sawn veneers . 5 or 6 mm thick and pressed on with poly glue . I used to use two pack glue but now like poly glue for that sort of thing .

Originally Posted by auscab

You either have to lock the mitres with the dovetailed W Patch on the under side or you loose tenon then glue and peg it . Then seal both sides of the top when finishing .

Hi Rob, Whats a dovetailed W patch?. Because both sides will be visible, I think the loose tenon option would probably be more ideal. I've only ever done Mitre joints on planter boxes in the past with an old crappy Ryobi table saw so hopefully these will turn out better.

Originally Posted by auscab

Or like has been said you do it by veneering the center panel on manufactured board . Good plywood is the best. And it wont give you any trouble unless like the solid job its left in a bad environment. Its unlikely to show at the joints but veneer can lift off. I do them like that as well but use sawn veneers . 5 or 6 mm thick and pressed on with poly glue . I used to use two pack glue but now like poly glue for that sort of thing .

I've ordered a full sheet of 19mm 2GS American Oak on Birch Plywood from a place called Timberwood. Not sure how thick the veneers are on those however I know they're not going to be 5-6mm, would it make much difference on what I'm doing?.

Originally Posted by EagerBeaver71

Hi Rob, Whats a dovetailed W patch?. Because both sides will be visible, I think the loose tenon option would probably be more ideal. I've only ever done Mitre joints on planter boxes in the past with an old crappy Ryobi table saw so hopefully these will turn out better.

That's the dovetailed patch . Forget the W for now . Its a Long story . We put them in 2/3 the thickness on the under side then usually through pegged them as well . This one doesnt have the pegs .
IMG_1400.JPG

The loose tenon . These ones went in 40mm each side . Glued and to be pegged on those red dots each corner.
IMG_2810.JPG IMG_2812.JPG
That's an extension table leaf. One of two.
IMG_2819a.jpg

For this table top . Getting its Mitred top fitted.
IMG_2782a.jpg

Originally Posted by EagerBeaver71

I've ordered a full sheet of 19mm 2GS American Oak on Birch Plywood from a place called Timberwood. Not sure how thick the veneers are on those however I know they're not going to be 5-6mm, would it make much difference on what I'm doing?.

No it wont make much of a difference. And also its very different than sawn It'll be .6mm pressed then sanded. Polished and you wont be able to tell the difference. With sawn you can lay it then hand plane and scrape . Which is a start towards good patina . And you can strip sand and re polish a sawn veneered top many times if you need to . That's a quality thing .