Breadboard Ends

[Blackswanwood]

I am making a small table and want to use breadboard ends on the table top which I haven’t done before and would welcome some advice.

As I understand it the mortises need to be wider than the tenons to allow the top to expand and contract ... is it a case of just allowing a few mm each side of the tenon or is there a way of working out a specific gap to be left?

The top is 400 mm in depth - do I need to use several tenons or can I just use one long one?

Thanks.

 

[thetyreman]

my understanding is that they're through mortise and tenons, you don't make the mortise bigger deliberatley, they're held in with draw bore pins usually oak pins and not glued so that the top can freely expand and contract, if you have a 400mm top then you'd need quite a few tenons.

 

[MikeG.]

One tenon per board, and the centre one can be a snug fit. The outer ones I allow for about 3% movement out from the middle, so with something only 400 wide the centre will stay still, and the outer edges move up to 3% of 200mm or 6mm. So the mortises will be about 6mm wider than the tenons.......and keep them well inboard from the outer edge where the short grain can crack. Unless your wood is awful, or really damp, they won't move the 3%, but it's a useful rule of thumb which means you'll always be safe. Elongate your peg holes in the tenon to suit.

Don't make one long continuous mortise, because that doesn't leave enough guts to the breadboard end. However, do have a continuous tongue sitting in a groove almost the entire width of the breadboard end (the entire width if you don't mind it showing on the sides).