Wood Movement After Cutting Joints and Sanding

[TomInNC]

I was working on a table this week with legs that are connected by two tiers of crosslap joints. Immediately after cutting the joints, the crosslaps were very tight. My intention was to go back and trim them just before the glue up. Before assembly, I gave the parts a light sanding over the top (not in the laps/notches). Immediately after the sanding, the crosslaps were now loose enough to fit maybe 2 sheets of paper in the gap. Could this change have been because of the sanding? Or is this just wood moving? I'm new to joinery, so I am wondering if I accidentally committed some kind of cardinal sin I was unaware of that caused this change.

[wtnhighlander]

If you sanded any part of the joint, like the edges of parts, that might contribute, but simple shrinkage can account for that much, too. Any idea how much moisture was in the wood when you started?

[TomInNC]

3 hours ago, wtnhighlander said:

If you sanded any part of the joint, like the edges of parts, that might contribute, but simple shrinkage can account for that much, too. Any idea how much moisture was in the wood when you started?

I really tried to stay clear of the joint while sanding, but who knows. I tend to zone out when I am doing that kind of work.

I don't have a moisture meter, but this was some cedar that was leftover from an outdoor project I completed more than 3 years ago. The lumber had been sitting in the garage since then, so my official scientific guesstimate is that it was pretty dry.

 

 

[Chestnut]

It's hard to say if they were dry to begin with that much shrinkage is unlikely. I've made M&T joints and let them sit for a long while before assembly for one reason or another and they never changed much.