breadboard ends question

[Woodmonkey]

What would be the standard sized dowel used to draw bore a breadboard end on a table top? (A very meaty table top 2"+ thick)?
Also if I wanted a long bb end say 200mm on a 2 metre table how long would the tenon need to be?
Cheers
WM

 

[Racers]

Hi

I made a table from oak block worktops I used a 30mm deep mortice and 10mm oak dowels.
I used a birch ply lose tenon as I didn't have enough worktop to form the tenon, its o/k but a slightly deeper one I feel would be better 40-50mm.
I cut the mortice with a router and a 1/2" bit and two fences and planed down the birch ply to a good fit.

Pete

 

[Jacob]

The tenons need to be as long as possible but shorter than the mortices to allow for movement i.e. mortice nearly the whole width of the BB end say 180mm in your case. The dowels - 5/8ths ?. Positioned close to the shoulder to keep the joint closed- all movement then being hidden within the M&T

 

[Woodmonkey]

I think maybe I am confusing length and width, when I say 200mm breadboard I mean width, the length of the breadboard being the width of the table, say 1 metre. What I'm more concerned with is how deep into the bb should the tenons extend, if they are too long would it actually make them weaker? My concern is that with such a weighty table top, if someone tries to move the table by picking it up from the bb ends there will be a helluva force on that joint..
Pete, if you glue a birch ply tenon, what happens when the table expands and the ply doesn't? (Maybe not such an issue with laminated worktop?)

 

[Racers]

The ply tenon is glued into the breadboard which is side grain held only with dowels in the the table end grain no glue, with slotted holes in the ply on all apart from the middle one.
So the top can and does move.

Pete

 

[Jacob]

I think maybe I am confusing length and width, when I say 200mm breadboard I mean width, the length of the breadboard being the width of the table, say 1 metre. What I'm more concerned with is how deep into the bb should the tenons extend, if they are too long would it actually make them weaker? My concern is that with such a weighty table top, if someone tries to move the table by picking it up from the bb ends there will be a helluva force on that joint..
Pete, if you glue a birch ply tenon, what happens when the table expands and the ply doesn't? (Maybe not such an issue with laminated worktop?)

Thats how I understood it!
Yes is wide - hence the tenons need to be nearly full width to take the load if the ends are lifted or leant upon. Why not make them narrower? Their only function is to close the ends of the boards & joints and to keep them in line. If you look around you will find that most tables don't have them at all. They are more for things which must be kept flat (drawing boards) or which are subject to varying humidity and deformation (big kitchen tables)

 

[Woodmonkey]

Agreed, unfortunately this may be a case of form over function, the chap who wants the table made has seen a picture of one with wide ends and he wants the same.

 

[deema]

They need to be c3/4" thick and at least 4" into the breadboard. The biggest problem will be as Jacob states when the breadboards are sat upon, or the table is lifted by the ends. 8" wide breadboard unless quarter sawn in Oak is likely to cup badly when Morticed at these dimensions. You need bone dry timber. I would be tempted to make the breadboards out of three laminated strips to avoid this. I.e three strips 8" x 2 3/4" so that you can only see the lamination on the end. Usual grain orientation to minimise any movement.