# Breadboard ends: how much space for wood movement in mortises?



## HTX_woodworker (May 9, 2018)

I have a 28" wide white oak tabletop I'll be attaching breadboard ends to for a desk I'm making. The tenons will be 3" wide. I'm trying to determine how much wider the mortises should be.

In this article, the author mentions to leave the mortises in a breadboard end slightly oversized to allow for wood movement:
https://www.woodcraft.com/media/W1siZiIsIjIwMTcvMDgvMjMvMTEvNTkvNTQvMzYzLzUxX0JyZWFkYm9hcmRFbmRzMy5wZGYiXV0/51-BreadboardEnds3.pdf?sha=0262ef8caf95e0b8

However, he didn't mention roughly how much larger the mortise should be. I'm guessing this is largely dependent on the species used, the moisture content of the wood, and the ambient humidity?

I don't have a moisture meter, but may have to get one in order to come up with more precise data to help figure this out.

I also plan to be moving to the Saint Louis, Missouri area from the Houston, Texas area. From what I can tell, Houston has 75% average humidity, and Saint Louis has 70% average humidity, but Saint Louis has much dryer winters.

However, this desk would be in a climate-controlled environment at all times. From what I've read, the moisture content would still fluctuate, even with air-conditioning.

Any thoughts on how much I should allow for movement within the mortises? I am planning on drawboring each of the tenons, and widening the holes in all but the middle tenon. Cheers!


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## Unknowncraftsman (Jun 23, 2013)

About a 1/8 inch on each side. Trust me I'm a expert.


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## HTX_woodworker (May 9, 2018)

Thank you Aj.


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## HTX_woodworker (May 9, 2018)

I'm wondering if an 1/8 inch on each side is necessary, given the current conditions? The desktop is currently in the most humid environment it is likely to be in, as the ambient humidity is around 93% (short of moving to a rainforest, that is!). I was thinking that the tabletop will only shrink at this point. I can definitely understand putting an 1/8 inch on either side of the mortise if I was making this same project in the winter. What are your thoughts?


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## newwoodbutcher (Aug 6, 2010)

In my opinion, It doesn't hurt to allow for all the room it potentially needs. I think an 1/8th inch is ok, a 1/4" might be even better


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## rwe2156 (May 7, 2014)

Sounds about right. Assuming you know you need to elongate the dowel holes too….


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## HTX_woodworker (May 9, 2018)

Yes, I was planning to elongate the dowel holes, as well. Speaking of those, I've been debating as to the appropriate diameter: I was considering 3/8". Any thoughts on this? Should I allow about the same amount of movement (1/8-1/4" on either side) in the dowel slots?



> Sounds about right. Assuming you know you need to elongate the dowel holes too….
> 
> - rwe2156


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## HTX_woodworker (May 9, 2018)

That makes sense. When you say a 1/4", are you referring to 1/4" on either side of the mortise, or combined (i.e., 1/8" on either side)? Thanks!



> In my opinion, It doesn t hurt to allow for all the room it potentially needs. I think an 1/8th inch is ok, a 1/4" might be even better
> 
> - newwoodbutcher


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