Troubleshooting Paint Cracking on Door Frame Joints
The doors probably have glue just on the tenons instead of the tenons and shoulders. That means the gap that is there is actually loose, because of no glue. Something you might be able to do is to use a thick CA glue with an accelerator and seal the joint. Of course this means you will have to re-sand the joints for them to be flat again. Maybe even a medium thickness to let it get into the grain a bit.
From the original questioner:
Doors are outsourced and it's mostly on the mortise and tenon style. Proper amounts of glue was my guess as well. Sometimes the paint will peel off at the seam too. Thanks for the information.
From contributor J:
I have never been able to eliminate paint cracking on the joints. I make a solid frame MDF door for clients that do not want to see the paint cracks.
From contributor A:
It is common for door shops to put inadequate glue on paint grade doors. They are more concerned about staining clear finish doors with excess glue. Most woodworkers expect squeeze out and clean it off.
Mitered doors almost always crack no matter who makes them. The miter cracks due to expansion and contraction just like door and window casings. Perhaps you can ask your door manufacturer to use extra glue on your paint grade doors.
I have built many paint grade kitchens with no cracks. I always use MDF panels and glue them into the frames. Always enough glue that you have to clean it up.
From contributor B:
Wood moves. You can't stop it. Glue will only delay the inevitable. Finish will not keep it from moving. Miter the joint like the big boys do or bevel the joint so the crack doesn't show as well.
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