glued pieces are splitting,..

[arrya deefman]

Hello, I am trying to join purple heart and African ribbon mahogany. The edges have checked in a few places on the ph and the joint is separating after only two days. I wiped with acetone and glued using west systems 105 epoxy with a little sawdust and fastened with sheet rock screws. The wood lives in an unheated shop in a damp climate. I mill and glue, then move it into a small heated room to dry. I shape and sand and then the work has to sit a few days until the ph turns purple again but when I came back the project had failed. What am I doing wrong? If it makes any difference the wood is 4/4 cut into 1.5" thick rings about 8" diameter with an empty center and stacked two high. Ok, the spell checking is complete, I had no mistakes. Thank you for your time.

[Robatoy]

Did all the acetone have a chance to flash off? Did you over-clamp? That WEST stuff is pretty thin. Too much sawdust?

Just guesses.

[Doug Miller]

1. Storing your wood in an unheated, damp area.
2. Milling it before it dries.
3. Gluing it before it dries.
4. Not waiting long enough for it to dry.
5. Using sheetrock screws. You want wood screws for joining wood; a wood screw has a section of its shank that is unthreaded, so that the piece being screwed through will be drawn down tight against the piece being screwed into. When you use a screw that is threaded the full length of its shaft, the screw threads can interfere with pulling the two pieces of wood tight against each other.
6. If a joint is properly milled, glue and clamps will be sufficient anyway, and you don't need screws.
7. It's not clear from your description, but I wonder if perhaps you're attaching these pieces with the grain of the mahogany perpendicular to the grain of the purpleheart. If that's the case, then another part of your problem is using glue at all. Wood shrinks across its width as it dries, perhaps considerably (depending on wood species and moisture content) -- but shrinkage along the length is near zero. If you glue one board crosswise to another, you've almost guaranteed that something's going to break as the moisture content changes. Such joints need to be made with screws *only*, no glue, and the screw holes at the ends need to be elongated to allow for wood movement, e.g. ___ ___ (___) O (___)

The latest issue of Fine Woodworking has an excellent article on making table tops, which describes all this in much more detail.

[arw01]

What is the moisture content of your woods?

Alan