Case construction practices

A look at various methods of case joinery for kitchen cabinets. September 6, 2000

I'm curious about accepted case construction methods for kitchen cabinetry.

Are dado, dado and rabbet, etc., joinery methods, with glue-up, all that's required? Or are mechanical fasteners used in combination with these techniques? I've noticed high-end custom cabinet suppliers in my area using screws through the side panels (covering with an end panel where required). Is this common practice?

Also, are most face frames being constructed with pocket screws today? Is this appropriate for high-end cabinetry?

Forum Responses
Before quitting business, we used a slightly unusual system of case construction, based on a tongue-and-groove joint. We machined a 1/4" x 1/4" tongue on the ends of cabinet decks and hanging rails and on the edges of cabinet sides. A corresponding groove was machined into the back of the face-frame stiles to accept the sides and similar grooves were machined into the case sides to accept decks and hanging rails. This system was a bit less forgiving than a dado sized to the thickness of the sheetgoods, but formed a perfectly square and rigid box.

The sides were assembled onto the decks and hanging rails, then screwed using a hardened-nib screw that cut a neat recess as it was driven home. Screws were hidden or covered by finished end panels. Face frames were then glued and clamped onto the pre-assembled boxes.

We used a horizontal mortiser for face-frame construction. We cut slots in the rails and stiles, and assembled with a hardwood spline planed .010 undersize for glue clearance, ripped to width, and batch chopped to length. We considered pocket screws for face frames, but never took the time to fully investigate the system.

Id like to hear from those that use a pocket-screw joint too, especially those that switched from mortise or dowel construction.
Michael Poster, forum moderator

This could be a very lively topic. At the risk of being called archaic, I vote for the rabbet and dado as my preferred method of joinery, especially melamines. I have had too many case parts pull loose from cabinets built with methods of construction which incorporate the use of fasteners. While the use of butt joints with fasteners seems appropriate for high-volume cabinetry or commercial casework, I prefer the rabbet and dado for the custom work I do.

I get unrivaled strength and accuracy. I can dictate to the assembler the locations of fixed shelves. The dado proccess is relatively simple and fast. I get tighter joint lines. The assembler can hold the parts together more easily. Glue, light pressure, and a few staples hold things together until the glue sets. At that point the strength attributes really shine. Then I veneer the finished ends, thus leaving no nail or staple holes.

I work from a small shop, so the cost of space and machinery make this system very practical for me. As for face frames, I avoid them unless the project calls for them. Biscuit joints and clamping 'til the glue sets also works well for me. Saying all this, I realize that different methods work better for different applications. This way works well for me.

Pocket holes for face frames (the Castle Tool system, which doubles for some case-assembly holes, too) work just fine - dowels are probably still preferred for high end, but I haven't had failure problems in twelve years of use.

I'm butt-jointing most casework, and am totally sold on Confirmat fasteners, which are kind of like big, threaded dowel screws. They hold like mad in any material (pre-drilled with a proprietary bit and drill assembly), are inexpensive (.02 -.03/ea), and easy to use in the field, if necessary.

I've gone to using 1/2- or 3/4-inch backs exclusively, stapled and then Confirmatted, which makes for a hellishly-strong case and solid installation!

We build institutional-grade frameless casework. This is the most demanding grade of casework you will see. You will very seldom see an institutional-grade spec written with anything less than 8mm dowel joinery, and in many cases specs call out 10mm dowel construction. In my opinion this yields the highest strength and best production capacity of any method. We previously used pocket screws (Castle machine) and had many, many failures.Many kitchen cabinet guys will argue on this point.

Dowels, European assembly screws and blind dadoes all meet AWI premium-grade specs.

I'll throw my two cents in here. I always dado and nail my cabinet boxes, but I am about the only local shop that does. I also avoid face frames like the plague, but there are times when it is aesthetically correct.

I learned cabinetmaking from a boat carpenter. If he had it his way, everything would be mortised and tenoned, and assembled with marine epoxy.

For melamine case-to-face-frame I use a sliding dovetail. This is fast for assembly and it holds. For plywood sides, biscuits work for me.

As a small shop, we have used various methods for frameless contruction. The Confirmat screw is the best short of buying a doweling machine. Great strength, reasonable price. We hold the case together with a few staples to assist with hole boring and fastener insertion.

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

Comment from contributor G:
I have found a combination of biscuit joinery and pocket screws is excellent for carcass assembly. The screws act as mini clamps in that even when the glue is wet, the cabinets are rigid. Also, pocket screws for face frames work well.