Accurately Squaring Cabinet Boxes

Methods foraccurately squaring frameless cabinet carcasses. October 16, 2003

I started building frameless cabinets and am looking for a simple system of squaring the boxes. Case clamps are a bit too high priced for me at this time.

Forum Responses
(Cabinetmaking Forum)
After inserting your back into the grooves, use your tape measure to measure across the diagonal in both directions. When you are happy with the measurement, nail in the back. This will hold the cabinet square.

From contributor D:
I'm going to approach your question from the angle that assumes you know how to square a cabinet. One of the reasons folks shy from making frameless is because (without a frame) it is essential that the box be square, using nothing more than butt joints and some form of fastener. So then it is critical to start with truly square parts with square edges. I've always gotten a chuckle out of the old cabinet book sales pitch: "If you can make a square box, you can build a cabinet." Assuming one is able to measure "square," it's amazing how difficult it is to make a truly square box with the usual shop equipment found in serious hobbyist or start-up cabinet shops.

Let's put all that aside for a moment. You make square frameless cabinets with square cabinet panels, making sure the parts are aligned properly during assembly, and then you check and adjust them before and as you fasten the back in place. Never neglect to check the back of the cabinet for square before firmly attaching the back to the cabinet, since up to this point, the box can and often has a slight bit of ?rack? in it. The back then must be firmly attached while the cabinet is held in square, which will then hold the cabinet in square and eliminate racking, at least under most reasonable circumstances. Can you get by if your frameless cabinets are not square? Well, yes - sort of, but you will have to deal with it at installation, which can be frustrating and time consuming, and after all that effort, your end result may well be less than satisfactory.

It's hard and very time consuming to build frameless without a perfect cutting panel saw, automatic edgebander and a case clamp. If you go 32mm, then you have to add a line drill and/or construction line drill at the very minimum. I tried it the hard way using a Delta Unisaw, hand applied banding and loads of bar clamps. Not only was it very stressful and extremely slow, but it was equally as difficult to try and keep things square while gluing up.

I'm certainly not going to tell you what to do, but if I were in your shoes, I'd stick with face frame construction and purchase frameless machinery one machine at a time when funds are available. My first purchase was the panelsaw, then the caseclamp and then the auto edgebander. Later I added a construction/line drill and other machines.

We use some fairly good entry level equipment in our shop to do frameless boxes with a Holzer vertical saw and a small CNC. That said, our cuts are not always perfectly square. I'm only talking sometimes a 32nd out, but multiply that by 10 and you can run into install problems. What I usually do is assemble the boxes carefully, keeping all edges aligned, etc. Then when I apply the back, I make sure to square the box with at least two edges of the back, one side and the bottom. I also keep a framing square handy and lay it down the side to check that my plywood isn't warped. If it is, I'll put the bar clamp on and nail it straight. Another thing that helped a lot was ripping my bottom 36" and cutting it to size, then rip to 23 1/4, taking the remainder and cutting it to the required spreader width, i.e. 3 @ 4" each. This makes the spreaders exactly the same size as the bottom.

From the original questioner:
I will be using dado construction on my boxes, instead of dowels. I think that will help keep things square and in line. At this time, my two-man shop builds computer furniture. I operate my business in Barbados, West Indies.

I can only echo contributor D's statements about square parts. I consider the squaring of the boxes automatic when the parts are cut correctly. The crucial part of the box is the back. If all other parts are correct, then the back will square up the carcass if it's square itself.

Adding to what's been said about square parts and such, I lay the assembled box face down on a perfectly squared two-sided corner guide and staple the back panel into the dadoed sides and backs, following up with construction adhesive.

A good saw and sawyer are the most important, as stated. That said, most shops build square boxes every day. A drawer box that isn't square won't work properly, so I assume you are successful with the drawers. If you have a discipline that works for drawer boxes, try it on your cabinet boxes. Just a thought for those working through the transition to more sophisticated machinery.

Paul Levine (FWW Tauton Press) has a book and companion video on building frameless cabinets in a small shop. You might want to take a look at the method he uses, one of which makes producing square boxes pretty easy without all the fancy tools.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor L:
I highly recommend reviewing the product you are fabricating and sticking to one method for that item only. If, for example, you are building frameless and are just getting started, stick with butt joints and skip dado construction. If square is the problem and the caseclamp is out of budget, dado slip the backs in your cabinets from the top of the case hitting the deck dado, place an interior nailer in the case to start yourself off semi-rigid, and the back will help to square. The key to cutting square parts on a 10" Unisaw is flat tables on the feed, out and side supports. Process the panel in a head cut, then the rip. Cut all the case sides and then the decks/case shelves stretchers at the same time. I would skip the panel saw, but buy a good edgebander and machining center. The machining center can be programmed to square up and then proccess dowel points and system32 all in one place.