Need help fixing a chair!

Epoxy.

Lew

Based on your comments, I think you may not have the piece that is broken off? If you do, epoxy it back and add a couple of cross dowels for additional strength. If not trim the stub flat at the same angle, that is just cut off the roughness, cut a piece to replace the lost piece, glue it up, rebore for the back slat dowels. stronger than new.

Nice looking old chairs. Good refinish potential.

Frank

Yes the pieces are lost. I can patch it but I really didn't want it to look patched. Plus my biggest concern is that the wood will break again. Three of them broke and more than one post per chair.

Isn't it a design flaw?

I don't think so, seems like most of the chairs made are that way with the upper cross piece either doweled or M & T into the side rails. I looked around the house and most of mine are that way, with one set having the cross piece on top of the side rails.

If you glue a piece on it is likely that if it ever breaks again it will not be in the glue joint. The cross doweling could help, maybe take it so that it doesn't come through the front, only seen in the back, put them in both sides and they will match.

I fixed a double base neck and a guitar neck that way, both broken in the tuning section. Both came out great, have never broken again and are under a lot of stress from string tension.

Frank

I might go the least work path and glue up the broken end, especially if it fits well. Possibly use a (hidden) brad or two. The cracked off piece is not a critical stress point.