Two joining questions

[Pvt_Ryan]

1) When joining boards for say a table top do you just glue the edges or do you mortise and tenon the boards first before gluing?

2) I saw a dining room table in tesco the other day and the top "seemed" to be made from offcuts. All the pieces were roughly 25x25x100mm, is it even possible to glue that many pieces together and have any kind of strength?

Ryan

 

[Dibs-h]

the top "seemed" to be made from offcuts. All the pieces were roughly 25x25x100mm,

You mean a bit like those wooden kitchen tops that aren't made from full length staves?

If it is - then with the "combed" type of joints - I don't see why not.

HIH

Dibs

 

[Pvt_Ryan]

Yes, I think I did see a combed joint on the side now you mention it.

Are they "almost" as strong as full staves or are they considerably weaker (my son has decided that tables are clearly there to be climbed on).

Ryan

 

[danielddr]

Hi,

If you are connecting single narrow boards together to make a wider board then it isn't absolutely necessary to have anything more than glue holding them together as modern wood glues are amazingly strong. Of course you'll want to make sure that the edges of the boards to be joined are smooth, straight and form a tight join all the way along their lengths. Then just smear the glue and clamp the **** out of them until the glue sets up. The only issue with this approach is ensuring that the boards remain perfectly aligned during the glue up and stay that way as the glue hardens. For this you might consider making some form of joint to aid with the aligning. Personally I've found biscuits ideal for this as they are very fast to make and really accurate, but there are alternative approaches available.

Alternatively, if you're attempting to join shorter boards together to make a longer board, then you'll almost certainly want some additional form of joint connecting the pieces as the end-grain to end-grain join would be weak. On my cheapy Argos table, which also appears to be made from 'offcuts', the short bits have their end-grain terminated in a very tightly cut zig-zag pattern, which dramatically increases the surface area of the joint and enables the glue to provide sufficient strength. These zig-zags are cut with amazing precision and I really doubt that it's possible to match that without specialised equipment. Additionally I suspect that the final boards are glued up under enormous pressure, which simply isn't achievable with standard clamps. So whilst it's definately possible to make a rigid board in this manner, I don't think it's a practical proposition for most of us. Besides which, can you think of anything less fun than cutting and gluing _that many_ bits of wood together?

Cheers,

Daniel

 

[Pvt_Ryan]

Thanks for the explanation, It was just a sort of "hmm I am bound to have loads of offcuts left when i start doing more woodwork, I wonder if I can do 'something' with them".

But you are right in the "It's probably more effort then it is worth"

 

[Chems]

The main reason for adding some sort of extra joint when doing a table top is not stregnth but alignment.

If your adding biscuits, dominos or a floating tongue into a groove on both boards the boards are going to be less likely to slip upwards which means loads less flattening when you come to finishing.

I know a local cabinet maker who uses a finger jointer in his spindle moulder for this reason. Saves him loads of time jointing the edges on the planer and means that when he glues them up they will be in perfect alignment.

 

[WhyDi]

Good Evening,

...It was just a sort of "hmm I am bound to have loads of offcuts left when i start doing more woodwork, I wonder if I can do 'something' with them"....

Amongst many others, here is a way of doing 'something' from offcuts 25x25x100mm. This is the kitchen I have been lunching and dinning every day since nearly ten years. I'm a hobbyist woodworker of course and a professional could probably not spend as much time as I did assembling such small bits.

Enjoy your dinner :wink:
Best Regards

 

[Paul Chapman]

When joining boards for say a table top do you just glue the edges or do you mortise and tenon the boards first before gluing?

When jointing boards, I always use biscuits, Dominos or loose tongues. As well as helping with alignment I feel that they also add to the strength of the joint. In this one (which was part of a table top) I used two rows of biscuits as the top was thick

If you don't have a biscuit jointer or Domino, you could rout a slot (continuous or several short slots) and use loose tongues. The tongues could be made of plywood, solid wood or even MDF.

Cheers :wink:

Paul

 

[Benchwayze]

Have you got shares in Lamello Paul!
:lol: :lol:


All the best

John :wink:

 

[RogerS]

Have you got shares in Lamello Paul!
:lol: :lol:


All the best

John :wink:

No - but a Drive-By Clifton gloat of epic proportions! :lol:

 

[ondablade]

Was asked to look at a table bought from a furniture shop about nine months ago by a friend over the weekend which demonstrated rather nicely what can go wrong.

The top was glued up from roughly 50mm wide strips of 25mm thick approx of what looked like lacquered oak, and it had split right down the centre from bread board to breadboard to open up a gap of about 2mm - mostly along a joint, although in places the wood itself had failed.

He wanted me to glue and clamp it up again - I said I thought it was unlikely to work even if we could get the gap closed - that to sort the breadboards and maybe slit out the split and glue in a filler strip in something with a bit of give was probably a safer bet.

It looked very like the boob was that bread board ends had been fitted, but had mistakenly been glued along their full length. (there was no movement at all visible at the outer ends relative to the main part of the table top). I imagine that the oak strips making up the main part of the top must have started out a bit wet too.

It was a bit of an eye opener to see just how much force was generated, and how strong the glue was. It looks like what happened was that the main part of the top started to shrink, but as a result of being held at the ends of the breadboards pulled itself apart rather than reducing in width.

Whatever the glue was it was strong enough to both secure the breadboards (with only about a 15mm tongue), and to cause the wood to fail along the grain in the centre.

BTW I noticed a short piece in one of the good US mags recently that suggested that narrow boards don't really help to keep a table top flat - and that breadboard ends are generally not enough to prevent warping either. Better to go for good wood in whatever width looks right - with the right grain and properly dried. I can't say because I've never made a table, but it sounds promising as I'm personally not attracted to the idea of breadboard ends that will only ever line up once in their life....

 

[Sgian Dubh]

BTW I noticed a short piece in one of the good US mags recently that suggested that narrow boards don't really help to keep a table top flat - and that breadboard ends are generally not enough to prevent warping either.

Generally true, they usually, but not always, need to be thicker than the panel to have any real ability to prevent cupping and maintain flatness.

I'm personally not attracted to the idea of breadboard ends that will only ever line up once in their life....

The panel and the clamped end (aka a breadboard in Americanese) usually line up twice a year as the panel expands and contracts over the seasons. Slainte.

 

[Pvt_Ryan]

Wow, I thought I was getting 2 replies tops...

Thanks for all the replies and advice..

 

[Benchwayze]

PR,

If you use breadboard ends, bear in mind that some workers make a design feature out of the breadboards being about 1/2" (12mm) wider than the table top. This is so that if, as often happens, the top shrinks back leaving the ends proud, it doesn't show so much.

Just a thought, because breadboard ends do help keep a top flat. But whatever you do, wood moves, as we know.

Best of luck

John

 

[ondablade]

That seems almost to be the point John - you could argue that they are as much a styling feature as a functional construction element....