Originally Posted by MNsawyergp
For the back, you will need to rabbet out the wall side of the sides. If you plan to use 3/4" MDF for the backs also, the rabbet will be 3/4" in from the back edge and rabbet out 1/2" of the 3/4" thickness. In factory cabinets, they usually use 1/4" plywood for the backs and put a 1x3 inside the cabinet at top and bottom against this 1/4" back to screw the cabinet to the wall. If you use 3/4" ply for the back you won't need to do this, but you should make the top and bottom so they are 3/4 inset as well, so the back overlaps them and you can run screws through the back and into the back edge of the top and bottom.
Thank you, this is exactly what I was looking for. The only question I have, and it may be a "taste" or "opinion" thing, but is it necessary to rabbet the full 1/2"? I feel like I see people doing 1/4" or even less...but maybe they are wrong. My concern would be that if I use screws, as well that it would be easier to split the 1/4" remaining wood.
I have been reading up on joining mdf and the general consensus is that glue is the primary bonding agent...in conjunction with either biscuits or screws. It seems like screwing into the endgrain of mdf is likely to split the wood so I would need to use pilot holes or avoid it altogether. I was thinking about rabbeting the sides and back and using pocket holes in conjunction with glue. Then I would use biscuits for the face frames. My other option was glue and nails and then fill the holes as the cabinet will be painted. Thoughts?