# Cross grain joinery



## BalsaWood (Mar 25, 2015)

I noticed in tressel tables that there is cross grain construction in the apron. For example:

https://static1.squarespace.com/static/5446ce86e4b008b6c28db4ad/553bdca2e4b03925cdef1c2e/554d1844e4b0a8ade6d0083f/1431116552426/modern_trestle_dining_table.jpg?format=500w

How much cross grain joinery is acceptable before it blows up?


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## LittleShaver (Sep 14, 2016)

There is no apron on the the table in your picture. Where there are cross grain joints, they are probably M&T and are perfectly acceptable. The cross brace under the top is also likely attached with screws in slotted holes to allow the top to move.
As for how much is acceptable…It depends. Type and condition of the wood, joinery used, placement of glue or fasteners, etc. Less is better, too much is a variable.


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## CaptainKlutz (Apr 23, 2014)

+1 no apron on that table
+1 cross gain support likely has slotted holes holding the top down.

IME - typical amount of wood movement for a 30" wide top is 1/4-1/2" total as moisture changes from 0% to 15% typical for indoor furniture for typical domestic species of wood.

How much 'before it blows up' depends on joint type, and allowable wood warping. 
This topic is always spirited debate as everyone has different experience with furniture living at different RH values, and few have seen same pieces live for a hundred years and taken between tropics and desert.

Tons of references exist on WWW:
https://www.wood-database.com/wood-articles/wood-and-moisture/
https://www.popularwoodworking.com/materials/how-to-calculate-wood-shrinkage-and-expansion/
https://www.finewoodworking.com/2013/08/29/calculating-for-wood-movement

Easy to figure out wood movement. Fire up your calculator!

YMMV


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## SMP (Aug 29, 2018)

I think you are confusing gluing cross grain with cross grain joinery? Plenty of ways to join pieces cross grain to allow for movement, from dirt cheap z-clips, slotted holes as mentioned, or intricate joinery techniques.


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## BalsaWood (Mar 25, 2015)

Oops- that is the wrong picture that I provided. I was wondering what if the face was aligned with the edge instead of what you see now in that picture which is edge to edge.


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## rwe2156 (May 7, 2014)

What are you talking about?

A trestle is made using mortise and tenons.

Just gluing to boards together face to face cross grain can be done, but it is not structurally sound. In some cases a half lap joint is used.

Maybe that's what you're thinking about.


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## wormil (Nov 19, 2011)

What they said above, the cross piece on the underside is a support or batten, which are usually attached with screws through slotted holes and help support the top and keep it flat. The slots allow the screw to move with the top as it expands and contracts. It is performing a similar job as an apron but we don't call it that.


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