Squaring Up Cabinets

What's the best way to keep cabinet carcasses square and is it worth it? Cabinetmakers share techniques and opinions. August 14, 2007

When we build cabinetry in my shop, I always fight to get the cabinet box perfectly square and find that this takes up valuable time which I am starting to think is unnecessary. Our face frames are always dead on and that's what really matters. Now, if your cabinet was 1/8" out of square, but your face frame was perfectly square, would you let it go or would you fight with the cabinet to get it perfect as well? I have heard from a lot of cabinetmakers that they don't even check their boxes for square, just the face frames. I, on the other hand, am a perfectionist and seem to go overboard sometimes.

Forum Responses
(Cabinetmaking Forum)
From contributor R:
Square can be interpreted in several ways. Do you use an actual framing square? The problem with that is sheet goods are not usually flat. We typically go by the diagonal and it's relatively quick, painless, and quite accurate. It's the back on our cabinet that keeps the box square.

From the original questioner:
I square diagonally, but sometimes when I turn the cabinet over after attaching the back, we're a bit off on the front. This is caused by different factors such as crosscuts that are slightly out of square. We have tried different crosscut jigs as well as sleds and still find it tough to get consistent crosscuts on wider panels. Thanks for the response.

From contributor L:
I try to get everything within 1/32" between diagonals. The problem with having a square face frame and an out of square cabinet comes at installation time, when they are using plumb and level. If it is out of square, you make the installer choose between plumb or level because both cannot be achieved with an out of square cabinet. An out of square cabinet can also pull a perfectly square face frame out of square when you attach it to the carcass. The back will square up the back of the cabinet but will not follow through and square the front up all of the time. With my glue and dado system, it is very unlikely that the back will square up the front. Everything needs to be as close to perfect as possible. All the little mistakes add up and at the end you may have a cabinet not worth selling/saving.

From contributor B:
This is one of the differences between a euro cabinet and face frame. Euro we have to be perfect to make it work. If your face frames and boxes were as perfect, your life would be much easier. Why? Everything will fit without question and no adjustment will be necessary. I can build a drawer stack and never touch the adjustments. In the end I bet it would take less time. Just my opinion.

From the original questioner:
Don't get me wrong. Perfection is what we strive for. Everything that is built in my shop leaves as perfect as it possibly can. It's the oddball cabinetry that sometimes poses a problem. For instance, I am building a built-in toy chest for a very high end project and because the top has to open, I don't have any room to install corner braces. This is causing the plywood to push to one side or the other. There is no diagonal support to keep the sides where they belong. All our measurements are exact to the 32, but because I can't support the sides, they are leaning to one side approximately 1/8". This is where I would rely on the face frame to keep my cabinet square. As far as where my cuts are out of square, I'm talking daylight under the square edge and only on wide boards - nothing more. I'm sorry, I should have been more clear. What would you do in this situation?

From contributor O:
You say it is built in - are using a back? What about a nailer to go across the back? What about a nailer to go across the front on the inside? 3/4 thick bottom squares the box from the bottom.

From the original questioner:
The cabinet has a solid 3/4" back as well as a 3/4" bottom which is in a dado joint on three sides. The only problem area is, if you're facing the cabinet, the front/top of the cabinet. I installed a 1x4 solid nailer on the front of the cabinet but that doesn't keep it square. I'm trying to keep the two sides from wanting to pull one way or the other without having any type of visual support.

Here is a picture of that cabinet. The face frame is cope and stick with 1/4" birch panels and my top will be the same except for a heavier material to support rich children jumping up and down on their brand new cabinetry. The only thing I can really do in this case is brace the cabinet square and attach the face to hold it in place. Anyone have any other ideas?

From contributor O:
How about the 3" +/- portion on the top that overlaps the top of the case on the left hand side and the right hand side? Keeps the case square, and is more than acceptable.

From the original questioner:
Not sure I follow. Overlaps?

From contributor O:
Are you saying the box is racking and you don't have the face frame on yet? Attach - it'll hold. You don't really need corner blocks if the back is solid and so is the deck or bottom.

The top overlaps - the box, say, is 60'', the top 62" for grins, the left end and right end is whacked off at 3" each. These become permanently attached to case top and the top is now 55 and 13/16 wide dropping down between the two 3" pieces.

However you split it, the case will become rigid once you attach the face. Call it what you will, it is a panel and that panel now completes the rigid square, just like a hope chest - they don't rack.

I think I misunderstood you and I didn't know that the face was not attached yet. It should hold it square without any problems. And you can just place a full piece lid on it. As everyone mentioned above, the back squares the case and after years of cutting square parts and building square cases and cabinets, I have a motto with the new hires - follow what I have outlined, build the box, and if it's not square, beat it into square.

From contributor M:
All I have ever done with face frame cabinets is attach the frames to square the front. The back is held square by the back piece or, in the case of backless, by the width of the hanging strip. I never even check for squareness with face frame cabinets. In fact, I never even check for squareness on frameless cabinets. I just check the back pieces themselves before attaching. You just have to check frameless cabinets when they are installed to make sure you haven't tweaked the fronts.

From contributor N:
Find someone to cut your boxes on a CNC and your out of square problems are over.

From contributor J:
I build face frame style cabinets. I find the same problem with slightly out of square cabinets. I cut all my parts on a sliding table saw - plywood parts, nailers, face frames, etc. All the parts are dead on square. After I put the cabinet together, often it will be slightly out of square. There is no logical reason for it, as I strive to build a better cabinet.

Now on the frameless box issue, I had someone process and cut parts for me on a job I did several years ago. I wanted to do a job in frameless to see how it went. Everything was perfect, and the box was dead on square, installation was a breeze. And all of the Blum metabox drawers worked very well. I tried the Blum metabox drawers in some of my face frame cabinets, and they didn't fit as well as they did in the frameless cabinets. I was hoping to use them on certain jobs, but it wasn't worth the effort. I needed more adjustment. Here's what I believe. Often my face frame cabinets get quite large, and the stress in the plywood (as it's never quite flat or true) contributes to the problem. If there's stress in any direction, this will pull the box out of square, just slightly. Frameless boxes are individual boxes that are one section each, and the melamine if it's flat would contribute less in stress to pull the box out of square. Frameless boxes are smaller and often have a one piece top that really keeps the box square. Does this make sense? You can have perfectly cut parts and near perfect assembly and still get an out of square cabinet. Here the frameless guys have an advantage over us - drawers work better and their system is faster and closer to a perfectly square cabinet.

From contributor T:
Build your face frames first, make them square, and build to the face frame. If your saws are cutting square, you shouldn't even have to check to see if your box is square or not... they will be as square as the cut that is made. Also, if you build in a scribe leaving your face frame overlap your box, the squareness is not even a big issue, as the only thing that connects together are the face frames. In reality, you could build a face frame cabinet an inch out of square and have no problems mounting slides or doors and no one will ever notice when they are installed... Of course I don't do this, just stating a fact.