Cross-grain Stiffeners

[Steve1]

I am making a hard-maple desktop glue-up.  1.12" thick.  28" front to back.
The plan was to put a few stiffeners on the underside.  Besides being stiffeners, they are locators for mounting onto the adjacent pieces of the desk, and a nice place to bury some threaded inserts.
I was wondering if there was a problem with my plan --- with the grain on the stiffeners running perpendicular to the table top glue-up, will I have issues with different expansion ?

See sketch below of the underside.

 

[flair woodworks]

Hi Steve,

As long as you allow the wood to move, you can do this. If you simply glue the cross pieces onto the bottom of the table top, you will have issues. Instead, use slotted holes and screws, or sliding dovetails to connect the battens while still permitting expansion and contraction.

 

[semenza]

And the domino makes great slots. I like washer head screws.

Seth

 

[Steve1]

Thank you for the feedback.

Yes, I was planning on gluing the stiffeners in.  Looks like I will be moving to plan B.

See below the bottom half of the desk.  I will still put 4 small blocks on each side of the desk top as locators into the spacers on the bottom half of desk.  You can see the rectangular spacers on the top of each of the two boxes.  I will pull the table top down onto those spacers. Using metal inserts and straight thread screws.  That will have to keep the desk top flat.  The holes in the box will have a bit of clearance, but the screws would be about 3" long, so if the desk top wants to move a little, it should have enough freedom.

 

[mcooley]

I too have used the Domino for the "mortise slots" with a washer and screw. I partially would plunge the cutter to make the desired depth so the washer and screw head were both flush.

 

[4nthony]

I haven't worked much with hardwood at the scale of your desktop so I don't have any real-world experience to pull from, but Keith Johnson put out a video where he adds some battens to white oak doors on a media console he built.

Perhaps his design will work for your situation. The relevant content starts at around 13:30.
=806s

 

[Packard]

I've seen this done. 

1.  Rip a length of lumber with 45 degree cuts on both sides. 
2.  Fasten that across the width by gluing and screwing the middle 3" only.
3.  Attach short cleats to fit tightly against the 45 degree angles. 

Essentially you are building a sliding dovetail.  But with independent blocks no longer than 3" fastened to the bottom. 

Generally, I have found that 3" is OK for cross grain attachment.  We use it all the time for shaker doors with no problem.