Purpose of tongue and groove board joints

[Tetsuaiga]

I'm sure this is a very basic question but i'm finding it a little puzzling.

If you were making a table why would you use tongue and groove joints when you could just glue them side to side then use something like table buttons or oversized screw holes to deal with shrinkage.

The only advantage i could imagine is the joint encourages the planks to meet at a level plane.

Maybe t&gb jointd arent any more time consuming than gluing as i imagine.

 

[dzj]

If the table-top is exposed to rain and such, then a glued up surface won't work so well and t&g is one way to deal with the matter.
If the panel is to be glued, a t&g gives you a level plane and larger gluing surfaces also.

Not really necessary, though. Gluing the edges is more than enough.

 

[DTR]

I wonder if it's an asthetic thing? In a time when everyone is used to seeing wide manufactured boards, T&G screams "I'm real wood!" (even though it may not be...)

 

[Mr T]

I think tongue and groove is used especially for large surface areas where the expansion would be to big to cope with at the edges if the whole area was glued up. The movement occurs at each join, as in floor boards.

Hoadley in "Understanding Wood" questions whether increasing gluing area with a tongue and groove actually improves the joint.

Chris

 

[AndyT]

I agree it won't be necessary for strength. If you have seen it on modern tables, I think it will be there as part of de-skilling the manufacturing process. Anyone can put T&G together and get a level surface, whereas gluing up plain butt joints needs a bit of skill in handling the clamps so they pull the joint straight together, not at an angle.

Also, T&G would give you a little bit less finished width than plain joints, which might matter if you are using specially nice boards.

 

[Tetsuaiga]

Interesting replies.

I think I can see with floors it might make more sense. I was taking apart a table yesterday, it had hide glue joints (not in the table top itself) so presume is fairly old. The top was screwed onto the two trestles then the holes capped over.

As far as glue strength goes, for a table top just plain butt jointed seemed perfectly adequate alone.

The manufacturing ease seems like the most reasonable explanation to me, though I could also imagine some people like the aesthetic of it.

 

[Fat ferret]

I think it's because t and g is widely available and it means you don't need to thickness glued up boards. However t and g table tops can cup quite badly so I use loose plywood tongues to join 45 x 70 mm stock. Like this.

https://www.facebook.com/26145630737749 ... =1&theater

 

[andersonec]

Personally would not use T&G in a table for the simple reason of food and dirt particles being embedded down there.

Andy

 

[RogerP]

A friend has a table I made many years ago (30?). The top is oak planks planed and rub jointed, no dowels, biscuits or whatever. No gaps or warps have appeared over the years.

 

[blackrodd]

I'm sure this is a very basic question but i'm finding it a little puzzling.

If you were making a table why would you use tongue and groove joints when you could just glue them side to side then use something like table buttons or oversized screw holes to deal with shrinkage.

The only advantage i could imagine is the joint encourages the planks to meet at a level plane.

Maybe t&gb jointd arent any more time consuming than gluing as i imagine.

The reason for T&G is to stabilise the edges of two or more boards where they meet, each supporting the other and stops gaps and draughts, as in flooring.
In days gone by loose tongues were used, mainly decent ply or hardwood strips that fitted the grooved planks.
In many instances these loose tongues were loose and not glued allowing some movement.
When given a small gap at the "meeting" edges to allow for expansion and contraction T&G boarding can be very stable.
Pine table tops were scrubbed with bleach and salt to clean them, they sometimes took on interesting shapes.
As now this is out dated practice the table tops can be gappy as they remain relatively dry.
Regards Rodders