Frameless Cabinet Carcase Fastener Choices

Kicking around a timeless topic again: What's the best way to put a cabinet together? April 10, 2012

I'm a finisher, but also trying to learn cabinetmaking, and enrolling in a college cabinetmaking program for next year. Before I start the program, I'm trying to learn all I can about cabinet construction, but one thing I can't seem to find anywhere is how cabinet boxes are constructed so as not to show any screw heads.

Many of the articles I've read talk about the use of dadoes and rabbets for backs, pocket screws, nailing, etc., but it seems each screw the boxes together. So how are the boxes (end panels) made without showing the screws? Are panels added to the ends after construction, then screwed on from the inside of the box? Are they veneered?

I've watched a couple of videos over where they've used mortise and tenon or biscuits to join boards. Is this how it's done?

Forum Responses
(Cabinetmaking Forum)
From contributor L:
Much has to do with the size of shop and the willingness to invest in the right equipment. Euro boxes can be very efficiently produced using the system developed in, of all places, Europe. That can range from highly automated plants to small shops, but the concepts are the same. Normal practice is to dowel the cases and case clamp them. Been the standard in Europe for 50 years. On this site you will find people that have adapted the system to their level of investment. The tradeoff is labor. I've heard all the arguments to the contrary. But I've got a small shop with the dowel and case clamp system for simple box cabinets. It works really well. There are all sorts of levels you can take it to. It can look traditional or modern. The hardware has been developed for frameless and adapted to face frames, sort of.

From contributor J:
Confirmat screws and cover with end panels. In my opinion it's the most economical, fastest and strongest method for assembling boxes. There are a million different ways to assemble a cabinet. You won't get the answer here that satisfies what you will prefer in the future. You must give them all a try and decide which one is the best for how you do things.

By the way, frameless cabinets are not fine woodworking, and any methods you see on the Fine Woodworking sites are overkill for building boxes.

From contributor K:
We use pocket screws. The sides are full height and then the bottom and bars are all pocket screwed. Back is fully captured. I also use plant-on ends. It just looks nicer with a door panel on the end. It also gives you something to scribe to the wall.

From contributor L:
I might have to take exception to Confirmats being the strongest. They are strong enough. Where they lose is in frequently causing the core to split around the screw. MDF is hopeless. We use lots of them for all the odd things we make. Dowels rarely cause a split and bond both sides of the hole. Shear strength is greater for both Confirmats and dowels than the material. With the right equipment doweling is faster, less labor. Doesn't matter whether you use plant on ends or not, it's the labor trade against the investment.

From contributor J:
I agree with you, but the key to your whole post is "with the right equipment." I didn't specifically state it, but I was implying they were the best method for someone that's not tooled up for frameless. For the average guy starting out wanting to build frameless boxes, confirmats are really hard to beat.

From contributor L:
A whole series of things can enter this discussion. I do totally agree with your statement about frameless cabinets and fine woodworking.

We are talking manufacturing here - business! If your business is manufacturing frameless cabinets, you should look to the best solution for your volume. While probably none of us here have the volume for a fully automated plant, looking for ways to reduce labor content is appropriate. Since our labor is really the only thing any of us have to sell, using less of it for every unit produced makes some sort of sense to me.

From contributor D:
Confirmats were designed for particleboard. Even 18g pins can split MDF. 7mm confirmats need a larger pilot hole when used in MDF. I switched to 5mm confirmats early on so that I could use the same bits and fastener for everything from MDF to 1/2" ply or PB.

A flip-flop boring machine is really the minimum requirement for dowels and confirmats. While I prefer dowels, I don't have a case clamp and use confirmats (with and without dowels) wherever I can.

Applied ends that match the rest of the exterior are needed if you follow the common practice of making the boxes out of a dissimilar material, typically melamine or prefinished plywood. Applied ends are more efficient to build and install (unless you're okay with scribe mold) than finished box ends. Applied ends have no design limitations; they can be edgebanded plywood, door panels, clipped corner assemblies, etc.

From contributor M:
I don't know when and where it became mandatory to screw or dowel cabinets together. I've been using dado and staple for many years on frameless cabinets. Works like a charm and is fast as hell.

From contributor L:
The original questioner asked how cabinets are constructed so as not to show any screw heads. Dado and staple won't pass AWI or the California equivalent. We sell nationally to architectural specs for commercial work, so we produce to those standards. If the work you do doesn't need to meet any standards, fine.

From the original questioner:
Thanks to all who have generously shared their knowledge in this thread. I'm learning a ton about how cabinets are built!

I'm a new member of AWI and want to make sure I'm learning all the right habits right from the get-go. It sounds like constructing with dowels is the way to go. Now I just have to tool up for it!

I'm curious why biscuits were never brought up - from much of my reading it seems that biscuit joining was made to replace dowels. Are biscuits an inferior method? I'll look into confirmats as well. Don't know anything about them, but it sounds like I'd still need a line-boring machine for that?

From contributor J:
Biscuits are fine, but they're very time consuming and require clamping and waiting. I use them only in an occasion where it's the only option on a joint with no fasteners showing.

All you need for confirmats is a drill, and a tapered or stepped drill bit. They're very nice in particleboard and MDF. On the very rare occasion I use either of those materials, I'll use confirmats. Drill 'em, screw them together, and move on to the next one. No clamps.

I definitely would not concern myself with assembling boxes with no visible screw holes from the outside. They will always be covered by the adjacent cabinet or an applied end panel.

From contributor L:
Contributor J, it depends. If you are talking residential cabinets only, maybe. But for commercial cabinets, store fixtures, etc., definitely not true. Much of our work is done with pre-laminated panels or melamine that is ordered in all the various patterns you can get in HPL. That work shows inside an out and often all the way around. It's still cabinetmaking, just not your typical kitchen.

From contributor O:
Once again, go to True 32. There you will find all the answers you will ever want about building frameless cabinetry and more.

From contributor J:
My apologies. My mind is crippled by residential custom kitchens. You are correct, contributor L. Although I have laminated over confirmats before, but that would not work with pre-lamed panels. Nearly everything I do is covered by another cabinet or end panel.

From contributor N:
I've been doweling for about a year now with a single spindle machine. I have yet to try confirmats, but I definitely see a use for them in some of the work I do.

1. Is a cabinet with only confirmats strong enough for a cabinet that hangs off a wall?

2. How do you apply finished ends? Do you flush the front 3/4" edge with the door of the cabinet? And how do you attach it to the cabinet?

I do some niche commercial cabinets with finished ends, which is why I like dowel construction. But for the basic residential boxes we do, I can see how confirmat might be a better choice given that I don't have a case clamp.

From contributor L:
Contributor N, single spindle? Or did you mean single head?

1. Yes!

2. We rarely do applied ends, but follow the designer's drawings when we do. Given a choice I'd flush them with the door fronts. (Full overlay on that door.) We attach them from inside the cabinet with screws.

From contributor D:
I'd use staples and screws before I'd use a stepped bit for confirmats. The whole point of using confirmats is that they both square and line the joint up for you, making assembly quick and accurate. The only way you can get that advantage is with machine drilled pilot holes. Drill bushing jigs are a labor intensive possibility, but stepped bit drilling - even with a Zentrix head - makes no sense to me. With a stepped drill (a tapered bit is totally unsuitable) you have to line up and square the joint manually to drill large pilot holes manually. There's nothing quick or precise about it. Using partial thread self-tapping/countersinking screws would be faster and tacking the joint in place with pins or staples first would make that task easier.

You can do all sorts of things with applied ends. The example image has two applied ends (one partial) and two matching scribes covering four standard boxes (melamine for the base) and no visible fasteners.

Click here for higher quality, full size image

From contributor L:
Photo of frameless cabinets going through shop now. Notice that even the short end of the small one is curved. This is the kind of work we Confirmat. Doesn't work well in the case clamp! True 32?

Click here for higher quality, full size image

From contributor E:
Contributor D, the point of confirmats is not just joint registration. In fact even with perfectly bored parts, confirmats have a little play. Dowels or biscuits or Dominoes will give better registration than confirmats, because they don't have threads.

Confirmats are an AWI premium grade fastener, assembly screws are not. The reason is that confirmats are essentially a threaded dowel, whereas assembly screws are thin and allow for more joint movement. The larger diameter and deeper threads of confirmats means that the threads cut in to the denser layers of particleboard that exist towards the outside of the panel, further improving joint strength.

With confirmats, glue is not necessary. This is a big advantage over dowels, biscuits, and Dominoes, in terms of ease of assembly and simplifying rework when it happens.

Biscuits are, in my opinion, a poor choice for corner joint assembly. They penetrate into each joint member only about 1/2". Easy to break if either joint member is flexed much. Dowels or Dominoes are a better choice - just as fast and easy to do as biscuit joints, but stronger.

From contributor L:
My take on case building and rebuttal to contributor E's post:

By using an old Philips screwdriver in adjacent holes, they can be made to perfectly line up just before the final tightening of the first Confirmat.

Confirmats also have the problem of often spreading the core. Keeping them back from the front edge lessens the problem of showing there, but it still exists.

It's sort of true that glue is not necessary, but you will have a better joint if melamine glued.

I've used lots of biscuits and they are perfectly fine for most applications. They are more time consuming.

Bottom line - If you don't feel the need to meet a formal specification and what you are doing meets you and your customer's standards, then stay with it. A doweled case made in a reasonably well setup shop is faster, saves labor and meets standards. The drawback, to get the advantages, is investing in a bore and insert machine and a case clamp.

From contributor D:
Contributor E, as you've stated confirmats are threaded dowels, remove the thread and you have a stepped dowel. You have three options for drilling dowel and confirmat pilot holes - machine (e.g. construction boring), drill jig, and freehand. All but the freehand option provide joint registration. The only option that can be compared to biscuits and dominoes is the drill jig. Those construction methods all require manually cutting individual pockets/holes and all provide some level of joint registration. Freehand drilling of pilot holes for confirmats or dowels makes no sense. The quality of the joint is dependent on your ability to align, square and hold your panels together while drilling the pilot holes. In this case, confirmats are just a fat screw with no inherent value.

Dowels and confirmats are equally capable of producing perfectly aligned joints in particleboard. The caveat is that the confirmat pilot holes need to be the same diameter as the confirmat shoulder and thread minor diameter. I don't know how common it is, but all the confirmats I have gotten from Hafele have been undersized on both minor and shoulder diameters (e.g. 3/16" and 6.8 mm). If your machinery/setup cannot produce perfect dowel joints, this is a feature because the difference in diameters allows you to tweak the joint a tad. A bit of glue on the joint will keep tweaked joints from sliding out of position. If your confirmat joints don't line up as well as your dowel joints, the ideal solution would be obtaining bits that allow you to drill proper sized pilot holes. My bet is that matching the minor diameter is all that's needed. An easier solution would be to use a few dowels (glued or not) with the confirmats.