Dove tail problem

[Bob Glenn]

I am making a toy chest for the grandkids. I have dove tailed SYP carcass on all four corners and got a pretty good fit with eight dove tails across 20 inches in each corner. I have been working out in the cold and the dove tails fit really nicely when assembled. I brought the assembled carcass inside for a week or so, then took it apart out in the garage to cut a dado in the sides to hold the bottom in place.

Yesterday, I went to reassemble the dove tails and they will no longer go together. When the first is aligned, the last is almost a sixteen of an inch off. I've brought the pieces back in the house, but no luck yet. It seems the sides are moving with the change in humidity at different rates.

Any advice is appreciated.

[Russell Sansom]

Do I understand that you've jointed SYP boards edge to edge to get 20" width? How old was the lumber?
I see two possibilities:
1) Moisture content was very high originally ( "green" wood ) and things have shrunk somewhat wildly. Are the boards twisted as well?
2) Moisture had reached homeostasis in your shop and when you brought them inside they shrank proportionately.
If one of these is the case, then,
1) Put the pieces in the location where they'll eventually live for a couple weeks. Make them flat again, cut off the dovetails, and start over with slightly shorter boards. Or...
2) Take the project back to your shop for a couple weeks. The dovetails should go back "about" where they were.

I have 20" table tops that move about 1/4" through the seasons.

[Bob Glenn]

It seems the ends, which are 16 X 20 have shrunk more the sides which are 20 X36. I think I'll try to put the ends in a more humid environment to get them to expand a bit.

[Mike Siemsen]

It is always a good idea to leave such things assembled, dry fit. It seems to help. It won't help you now though. Put the wide one in a dryer place until it fits again.
Mike

[Bob Glenn]

Just a follow up......I set the narrower piece outside (it's been wet and rainy) and the board has expanded about 1/16 inch in just two days. In the future, Ill leave it assembled until final glue up.