# Accounting for movement of table top.



## lateralus819 (Jul 22, 2012)

Hell all, I’m embarking on a table build and I’ve chosen maple/sapele.

I’m using 3/4” sapele for the main top and 8/4 for the breadboard ends. I’m going to glue another 3/4” piece of sapele the length of the other sides to make it 1 1/2” thick.

I want to add another 3/4” on the ends with the breadboards to give a more substantial tongue for the M/T.

I was thinking of running a 4” piece the length of it and glueing in the middle and doweling on the ends to account for movement, or would be be simpler to just just multiple tongues and add the material where needed for the tongues?


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## Steve Neul (Sep 2, 2011)

I think it would be unnecessary to build up the thickness of the table top to tennon for the breadboard end. Instead of running a actual tennon you might just run a 1/4" rabbet the top edge of the table and run a 1/2" mortice in the breadboard end. If you do double the table top I would glue it up extra long and cut the pieces from the top itself so it would be a end grain cut with the same wood.


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## lateralus819 (Jul 22, 2012)

Steve Neul said:


> I think it would be unnecessary to build up the thickness of the table top to tennon for the breadboard end. Instead of running a actual tennon you might just run a 1/4" rabbet the top edge of the table and run a 1/2" mortice in the breadboard end. If you do double the table top I would glue it up extra long and cut the pieces from the top itself so it would be a end grain cut with the same wood.


1/4" tenon and 1/2" mortise...shouldn't the tenon be the same thickness?


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## Midlandbob (Sep 5, 2011)

I think Steve was suggesting a 1/4 inch rebate on the top of the table leaving a 1/2. Inch tenon. Then a 3/4 board on the bottom with a 1/2 inch stop dado would make a type of breadboard. . This almost works but leaves exposed end grain at the ends of the top. 
If you do two breadboards each 3/4 with 1/4 stopped dados, you sandwich them on the 1/2 inch tenon to have clean ends. It works a bit better if the table rebate is 3/8 leaving a 3/8 tenon and 3/8 fore the top and bottom breadboards. You want the strength in the breadboards.
. The stopped dados need to be 1/2 inch longer than the table tenon for the table expansion.
I am just finishing a 36 inch wide cherry table top and calculate 0.36 inch expansion by peak of summer humidity. I made the breadboards an 1/8 inch long on each side to allow for the movement. It seems better looking to have a slight long breadboard than a too wide table top.
It make an easy mortise especially if you can hide the glue line in the edge shaping.
Bob


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## lateralus819 (Jul 22, 2012)

Midlandbob said:


> I think Steve was suggesting a 1/4 inch rebate on the top of the table leaving a 1/2. Inch tenon. Then a 3/4 board on the bottom with a 1/2 inch stop dado would make a type of breadboard. . This almost works but leaves exposed end grain at the ends of the top.
> If you do two breadboards each 3/4 with 1/4 stopped dados, you sandwich them on the 1/2 inch tenon to have clean ends. It works a bit better if the table rebate is 3/8 leaving a 3/8 tenon and 3/8 fore the top and bottom breadboards. You want the strength in the breadboards.
> . The stopped dados need to be 1/2 inch longer than the table tenon for the table expansion.
> I am just finishing a 36 inch wide cherry table top and calculate 0.36 inch expansion by peak of summer humidity. I made the breadboards an 1/8 inch long on each side to allow for the movement. It seems better looking to have a slight long breadboard than a too wide table top.
> ...


I was thinking of having my tenon 3/4" with a 3/8" rebate on the top/bottom with a 3/4" mortise on the breadboard ends.


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## Midlandbob (Sep 5, 2011)

If your main top is 3/4 , and you want the tenon to be buried in the breadboard, I would have thought a 1/8 off the top and bottom of the main top would leave a 1/2 inch tenon and keep the strength in the breadboard to restrain any cupping. Or maybe a 1/4 off the top and your added piece making the bottom of the mortice.
I'm sure whatever you work out will work well.


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## lateralus819 (Jul 22, 2012)

Midlandbob said:


> If your main top is 3/4 , and you want the tenon to be buried in the breadboard, I would have thought a 1/8 off the top and bottom of the main top would leave a 1/2 inch tenon and keep the strength in the breadboard to restrain any cupping. Or maybe a 1/4 off the top and your added piece making the bottom of the mortice.
> I'm sure whatever you work out will work well.


Guess i didnt think 1/2 tenon would suffice but i assume it should be fine?

My breadboards are 8/4 stock.


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## cabinetman (Jul 5, 2007)

lateralus819 said:


> Hell all, I’m embarking on a table build and I’ve chosen maple/sapele.
> 
> I’m using 3/4” sapele for the main top and 8/4 for the breadboard ends. I’m going to glue another 3/4” piece of sapele the length of the other sides to make it 1 1/2” thick.


You will have 8/4 on the BB's, and 6/4 on the sides. Is that a single plank, or a glue up? In any case there will be ½" differential between the BB and the sides.



lateralus819 said:


> I want to add another 3/4” on the ends with the breadboards to give a more substantial tongue for the M/T.
> 
> I was thinking of running a 4” piece the length of it and glueing in the middle and doweling on the ends to account for movement, or would be be simpler to just just multiple tongues and add the material where needed for the tongues?


What that sounds like is a pre-BB end. I would rather work with the stock thickness of the top in configuring the T & G.








 







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