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Cross grain joinery

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Forum topic by BalsaWood posted 07-08-2019 08:24 PM 441 views 0 times favorited 6 replies Add to Favorites Watch
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BalsaWood

157 posts in 1664 days


07-08-2019 08:24 PM

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?


6 replies so far

View LittleShaver's profile (online now)

LittleShaver

582 posts in 1125 days


#1 posted 07-08-2019 09:53 PM

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.

-- Sawdust Maker

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CaptainKlutz

1880 posts in 1999 days


#2 posted 07-08-2019 11:49 PM

+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

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View SMP's profile (online now)

SMP

1387 posts in 411 days


#3 posted 07-08-2019 11:59 PM

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.

View BalsaWood's profile

BalsaWood

157 posts in 1664 days


#4 posted 07-11-2019 12:03 AM

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.

View Robert's profile

Robert

3534 posts in 1986 days


#5 posted 07-11-2019 01:35 PM

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.

-- Everything is a prototype thats why its one of a kind!!

View Woodknack's profile

Woodknack

12903 posts in 2885 days


#6 posted 07-11-2019 07:14 PM

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.

-- Rick M, http://thewoodknack.blogspot.com/

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