Cabinet Construction: Pocket hole vs. dado joinery

[Iansaws]

I am in the beginning stages of constructing some new upper cabinets for our kitchen and I have a question about what joinery method is best to use. In the past I have always used dados and glue to assemble a cabinet carcass, but I have begun to use pocket hole joinery more and more things. I have recently come across some simple cabinet making instructions that included both my old dado method for thje carcass assembly and the use of pocket holes for the face frame assembly with a glue up for the face frame to the carcass.

I wonder if using pocket hole joinery along with glue might be a stonger way to assemble the carcass (by the carcass I mean just the box itself and the joint I am refering to is the one that joins the base and top to the sides). I might be able to use both dadoes and pocket holes, but that might be overkill. The first upper cabinet I intend to build will be 8 ft long and almost 4 ft high, with 2 uprights equally spaced in between. I know this may be difficult to install due to the weight (1 entire sheet of 3/4 in birch ply, plus a 4x 8 sheet of 1/4 ply), but I will manage somehow and it is why I think it needs to be extra strong.

Comments??

[JimD]

The cabinet is too big. You might be able to get it in place properly but your walls are probably not straight so it will be challenging to get it to fit. 3 smaller cabinets would be a much better idea.

In terms of construction, I like pocket screws and have seen tests in Wood magazine where they looked pretty good compared to more traditional constructions methods. I do not like the look of pocket screws, however, so I tend to use them for places where they won't show, the back side of a face frame is a good example.

With respect to the carcase, I like to use shallow dados because I think it helps a lot with assembly. Sometimes I use very deep dados so nearly only the face veneer is left. For instance, I built a kitchen in our last house of oak veneer cabinets with full overlay solid oak raised panel doors. The construction method was simple glue and screws in deep dados in the sides. I screwed the top and bottom on and plugged the screw holes (with oak plugs). You could find the screw locations looking on the top and bottom of the cabinets but we did not make a habit of doing that. I could then finish the inside and outside and have oak in both cases showing. If we had wanted under the cabinet lighting, I would have added a moulding to the under side to hide it.

I would not use pocket screws for the carcase unless you can hide them. I have not tried the special plugs they make for this but they might work if you put the pockets into a surface that is not looks at a lot (underside and top?). You could combine pocket screws with shallow, locating, dados.

Best use of pocket screws would be the face frame. A face frame adds surprising strength and hides the end grain of the plywood. Plus it is a traditional look. It wastes a bit of space in the cabinet, however, and is additional work. With 3/4 plywood carcases, I do not think you need the strength. If I were to build an eight foot long cabinet like you envision, I would probably build it the same way I did my last kitchen with glue and screws through the top and bottom into the vertical pieces with deep dados on the ends hiding the top and bottom. It is simple, fast, and strong. But you end up with European style cabinets. You could add a face frame if you wanted, however. If you don't, you have to veneer the edge of the plywood before adding the doors.

Jim

[gsmittle]

My local PBS station is rerunning Nahm's series on kitchen cabinets. He cuts a dado, then drills screw holes in the dado (from the dado side), then countersinks the hole on the outside. If the side of the cabinet is visible, then a panel covers up the screws. Pocket holes for the face frames.

All that being said, I use pocket holes a lot, especially for shop cabinets, where I don't care if the holes are visible. For #1 Son's Eagle project, we built bookcases with pocket holes on the outside and used paint-grade plugs in the holes. They went together fast and easy (great for a bunch of non-woodworking, barely-used-a-power-tool-in-my-life scouts). The plugs do stick out a bit, however, and require flush-trimming. (I used a trim router with a custom base and straight bit) before painting. The plugs were nearly invisible after painting, but I don't think they would work for fine furniture.

Just my 2˘ worth…

g.

[gary]

I've just built a cabinet using this method (pocket hole for the face frame and tongue&dado for the side to front joint. The only thing concerning to me was the fact I had some narrow face frames where two cabinets met so I had to be very careful with the dado depth so it would not hit the pocket screw. Hope I explained that well enough.

[Iansaws]

More info that I forgot

I forgot to mention that am going to paint the new cabinets along withthe old bottom ones and that since I am just going to build new doors for the bottom cabinets, I am putting a 2 x 3/4 in poplar face frame on the front. The pocket holes will never show if I do use them, so that is not an issue. Strength and simplicity are my main concerns here. I am really just duplicating the cabinets that are already there, just making them taller and building new doors. The cabinet that is there now is 8 feet long and about 36 in high. The kitchen walls are solid pine paneling, even behind the cabinets. In fact the present cabinets do not have a back to them at all...just the pine paneling which is all painted white now. I may leave of the back off these new ones as well if I don't need it for strength or to help square it.

Do you really think I will have problems with an 8 ft long cabinet if that is what I am replacing anyway? I have been a little worried about this.

From the advice received so far, it sounds like it would be best to use a 3/8" dado for the carcass joint as the simple instructions i refered to suggested and save the pocket holes for the face frame.

[JimD]

The additional detail helps. Before deciding to build an 8 foot long cabinet, I would take an eight foot long straight edge - could be the factory edge of a piece of plywood - and check to see that the wall is straight. Pine paneling seems like it has a better chance than drywall of being straight but I would still check it.

I do not like 3/8 deep dados but others do. I like shallow, like 1/8 inch deep dados. If I remember right, Norm uses shallow ones too. The theory of deep dados is they add gluing area. The theory of shallow ones is that the extra area is not necessary, is difficult to get glue on because it will transfer to the surface if you get just a little too much, and the deep dado weakens the piece you cut the dado in. I want ust enough dado to show me where the other piece needs to be fastened. Plus the shear strength of the edge is handy if they are in a vertical piece.

I like melamine particle board for white cabinets. The melamine is much more durable than paint. But you have to work cleaner - like no pocket screw holes where they would show. I have built them without a back by putting a 3-4 inch wide strip across the back for attaching them to the wall and squaring them. I have used iron on edging and flush doors but you could put a solid wood face frame on them. I think using the same wood species as the doors would be a good look but it would be more typical to use poplar and paint it white.

Jim

[cabinetman]

An 8' cabinet would be a chore to install, but you would use less material than three cabinets. One long cabinet would find the high spots on the wall, and there would likely be minimal shimming.

If you decide to do three cabinets each having their own face frame call the first "A", the second "B", and the third "C". If you've installed the face frame on the cabinets, lay them on their backs and line them up so the face frames are as close to flush as possible. Start with "A" and "B". Clamp the two FF's together. From whichever side you are comfortable drilling and screwing, drill pilot holes and countersink in at least three places (top, middle, bottom) from one FF into the other. Make sure the holes are not drilled where hinges will be installed. Insert screws that will be shorter by 1/4" to 1/2" than the ones you will use when installing. Bump screws in tight. Remove clamps. Do the final scraping or sanding on the two FF's at once so they are flat and even. Then go to the "B" and "C" cabinets and do the same thing, etc.

When installing, after placing them where they are to go and leveling them, screw cabinets to the wall, but not up tight. Using the slightly longer screws, align the FF's, clamp, and insert screws into the same holes and bump tight. Then do the final tightening of the cabinets to the wall. If the wall is not flat,(how many are?) shimming the back of the cabinets may be necessary, so that there is no strain on the FF's. This method helps make final alignment easier.

As for the joinery, I use a 1/4" deep rabbet and dadoes. I don't use pocket screws or biscuits on cabinets or for face frames. A much better joint for FF's would be half laps. Face frames can be just glued and clamped to the cabinet.
.

[Mr__Bill]

Personally, I would build the 8' cabinet. Check the wall and recess the back enough so you can trim the top and bottom to fit the wall reasonably well. A trim piece or wall treatment (ie tile) will cover the gaps. Shims where the screws hold it to the wall and you are done. It will take two people in addition to yourself to do this without destroying someone or something. If the wall is really out of flat build a frame where the cabinet will be and scribe it to the wall and then just mount the cabinet to that.

The real trick to an 8' cabinet is keeping the front flat so the doors close evenly. It is real easy to warp it when attaching it to the wall. Stretch an X string diagonally from the corners and keep the intersection point just touching. That way the front will be flat and the doors will close right. When I do an X string I stretch the first two and then add another on top of the first one. That way one string is between the other too and if all are touching then it's flat and one string is not just holding the other down. Don't use chalk line, it gets real messy quick.

I would also use shallow dados on the carcass and pocket screws on the face frame and dado the FF to the carcass. I would also put the back on it. That will help to keep it clean inside and will look better too. Not to mention it will keep it square.

good luck

Bill, over here in the rain

[cabinetman]

The real trick to an 8' cabinet is keeping the front flat so the doors close evenly. It is real easy to warp it when attaching it to the wall. Stretch an X string diagonally from the corners and keep the intersection point just touching. That way the front will be flat and the doors will close right. When I do an X string I stretch the first two and then add another on top of the first one. That way one string is between the other too and if all are touching then it's flat and one string is not just holding the other down. Don't use chalk line, it gets real messy quick.

Crisscrossing strings sounds like an interesting theory, which I have never used. The downside to that would be if the center of the cabinet run is closer to the wall than the four corners, the strings may touch if the four corners are on the same plane. The strings would give a false sense of flat. It would also be difficult to hold the corners (ends) of strings, or mounting the four corners without leaving holes from fasteners.

Ideally, the best way to get a flat front is to hang the doors and see how they lay. Adjustments with shims will move out-of-plane doors to hang correctly.

I would also use shallow dados on the carcass and pocket screws on the face frame and dado the FF to the carcass. I would also put the back on it. That will help to keep it clean inside and will look better too. Not to mention it will keep it square.

good luck

Bill, over here in the rain

Assembling FF's with pocket screws IMO is a weak joint. If that is done, and the FF is dadoed to fit the carcass, the dadoe reduces the contact area for glue in the joint, and dado may run into the pocket screws. Machining a dadoe in the FF also reduces its mass making it more vulnerable to bending if the carcass gets stressed to rack.


Machining the FF can also be an element of frustration. One would be having the dadoes stop and not exit the FF. Another would be if the FF is flush to the carcass the dado would actually be a rabbet. So, having a perfect alignment method is an overkill if done perfectly and very time consuming. The FF would still have to be clamped.

FF's can be just glued and clamped to the carcass. If need be a few brad nails just to hold its position could be used when clamping.

A well fitted back will square the back side of the carcass.
.

[drumpriest]

I've done dado cabinets, pocket screw cabinets, and loose mortise and tenon cabinets, and combos of these for different applications. Generally they are all pretty darn strong, but which I choose depends upon the use.

Dado cabinets will hold more downward force than pocket screws or mortise and loose tenon, because you have the full strength of the wood involved with a dado in that direction, rather than the 1/2 surrounding the screw, for instance. Pocket screws are easiest/fastest, and pretty strong as well. I recently used them to build my new upper cabinet carcasses, but I did this knowing that I would be attaching a solid wood face frame on the front, and a ledger board beneath it during installation, these add strength.

I'm not a fan of pocket screws for face frame, to be honest, they have caused me more stress than results. I find mortise and tenon to be best here, as it assembles easily and aligns well, but dowels also work well, and are easier if you don't have the right tools for mortise and tenon.

As Cabinetman says, the back panel adds a ton of strength and squares the cabinet. I also added a mounting board at the tops of mine that was about 5 inches wide, this also squared the cabinet, added strength, and ease of install. I just screwed into this 3/4" plywood piece right into the studs.

Lastly attaching the face frames, again as Cabinetman says, glue will suffice, but can make it difficult to align things. I use a couple of biscuits along each side to help ensure alignment, then glue and clamps.

That's my take, here is a link to my new uppers, that I installed this week.
http://www.bt3central.com/showthread.php?t=49033