I am doing a kitchen in solid cherry, where the doors will have breadboard ends. I plan on doing a tongue and groove joint all the way across where the breadboard meets the panel. I’m wondering how much of the joint I should glue.
I’ve seen recommendations to glue about the third of the width of the joint... but this is for a dining table, which can be 40” wide... so that would mean about 13” worth of cross grain gluing. So, assuming this recommendation is sound, would that make it reasonably safe to glue, say, an 11” breadboard joint all the way across its length? Because I don’t see the difference between 11” of width out of the middle of a wider table top, and 11” of width comprising an entire door. Right?
I’m not looking for any guarantees, or an exact scientific number that’s going to hold in all situations. But I don’t think anybody would worry too much about gluing a 4” wide table apron all the way across its width. So what’s the rough cut-off where you’d start to worry about cracking? 6”” 8”? 10”? 12”?
I’m leaning towards gluing the middle 10”, and for doors wider than that, making a spring joint on the breadboard piece, so the ends theoretically stay tight without glue or mechanical connections.