I have a dickens of a time getting my cabinet carcasses square. Even with rabbits and dadoes, and using clamping squares, they’re always out of whack. It’s one of those things that seems so easy for everyone, and I just can’t get it. My pieces just keep sliding around. I’m thinking about getting a couple Krieg corner clamps. Curious what you all think about these and corner clamps in general.


Are your parts square, true and plumb to start with?

Please don’t quote the trolls.
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Corner clamps won't yield a square cabinet if the parts aren't square to begin with.   It's not that easy to make parts square in X-Y and Z, especially multiples, but that's the key.  I suggest you carefully measure the diagonals of your parts to see if they are truly square.  To check if the edges are square, stand them on edge and slide a square up to the face.  Anything other than 90.0 degrees will be easy to see.   

I also helps if you can clamp or tie down your assembly to a flat surface as you are doing the assembly. That eliminates alignment problems in one plane so you can concentrate on the other two. If all of the pieces are square to begin with, it should just fall into place with minimal coaxing.
The clamping squares I had weren't square....

How do you build your cabinets? The order in which you assemble things seems to matter. For what it's worth, I have never had much of a problem with out of square cabinets, mostly because cabinet boxes that I build (like traditional kitchen cabinet types) end up getting installed where being square doesn't even matter, and the integrated type that go into most of my furniture can be put in position with very little effort.

That said, it depends on how you build your cabinets - not only the pieces that you use and their orientation, but also the order in which you assemble them. If you reconstruct that, you can see how an error would compound itself.
Like others have said, start with square parts and the rest goes rather smoothly. We just made 30 1/2" Baltic Birch drawer boxes with dadoed bottoms. All parts were cut square and the bottoms were cut snug. When they were assembled, the bottoms automatically squared the boxes. In my shop, I just made 10 flat panel doors. The panels were sized snug and square. When I assembled the doors, evry one was perfectly square.

Moral is, start with square parts, the rest falls in place.
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(05-07-2023, 05:03 PM)David Stone Wrote: I’m thinking about getting a couple Krieg corner clamps. Curious what you all think about these and corner clamps in general.

I have a set of 4 of them. Like others have said, don't rely on them to give you square, but they act as a very helpful extra set of hands if you're assembling them alone.

edit: I mispoke - mine aren't Kreg, rather, Rockler:
Problems like this usually go back to parts prep. I've never used corner squares for assembly, I check for square after its together and fasten the back. If everything is set up right, it should be pretty dead on.

Before starting a cabinet project, you should check machines and fixtures for alignment.

Blade perfectly square to table: Cross cut a board, flip and clamp together lightly if the resulting board is not straight, the blade isn't square to table.

Same thing if you use a miter saw. Just keep in mind a lot of them do not hold settings well and need to rechecked during the project.

Same thing for track saw. The can definitely go out of square.

All this is especially true for building frame and panel doors!
I have several squares like these.. I believe Peachtree has some cheaper ones.

I use quick clamps to hold the "squares" to the case.
These squares are not "machinist level tolerance" but they help a lot.
Also, measure diagonals.. It's hard sometimes when a carcass is all clamped up, but do the best you can.
I'm not 100% accurate either, but usually I can get it close enough
Also it helps to make the back of the case perfectly square.
Corner Clamps for Cabinet Carcasses?

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