As I mentioned in another thread somewhere here, I'm planning to make replacement cabinet doors for our kitchen. Simple frame & panel "Shaker" design, as seen in the jpg I attached.
Question: Is 3/8" a sufficient depth for the panel groove in the rails & stiles, and for the tenon length on the ends of the rails? 1/2" just "seems" better to me for strength purposes. I only ask because in our previous home, I had installed Kraftmaid cabinets with similar doors, and one of the corner glue joints had cracked due to opening against the adjacent door edge. Sort of a levering effect, I guess. Those doors were grooved about 3/8" deep, & possibly less.
An added advantage with my new doors will be that the panels (MDF) will be fully glued into the rails & stiles, which will add some degree of strength, I suppose.
Any thoughts/comments appreciated, as always.
Since you are gluing MDF panels between the stiles and rails, you really don't have to worry about a 3/8" or 1/2" depth. Either one is going to work and the difference will be insignificant. The glued MDF panels will add a significant amount of strength in the XY plane. In other words, if downward force is applied to the cabinet door handle, the hinges will probably be damaged before the door is damaged.
The Z plane is another story. If the force applied to the door is in the direction of the door opening or closing, then the amount of strength the 1/2" adds over the 3/8" is more, but not that much more. The glued MDF panel will also add some strength.
You will also need to think about the longevity of your cabinet doors. Your glued 3/8" deep joints are dependent on the glue holding up over the years of use. A properly designed, cut and assembled mechanical joint will hold up longer than a joint that has simply been glued.
When I am after very strong joints on two (2) pieces of wood being joined at an angle, I use a bridle joint. Some people don't like the end grain look, but with the correct wood, sanding and finishing, the joint can be very attractive.
The bridle joint can be made even stronger by adding a "mechanical" hold. By drilling a couple of 1/4" holes through the bridle joint and gluing in some 1/4" dowel, the bridle joint becomes even stronger. Make sure the dowels fit very tight and you won't even need glue.
The bridle joint can be made with a hand saw, a band saw, a table saw or even a router table.
The photo below shows a handle for a dust collector cart, that has multiple bridle joints. The wood is white southern pine.