Joint Strength

[cabinetman]

In my location, the humidity in the morning could be 15%-20%, and in the afternoon it could be 95%. The discussion of movement in your situation may not be as drastic as you contemplate. Unless it's taken outside when it's raining, and then moved inside (which will likely not happen), the humidity indoors usually stays at a reasonable range.

There may be some separation to the joint in M&T, or with dowels, as the major visual joint is a butt joint. I find it would be very rare to have dowels snapped off (at least I haven't seen that ever happen, or ever heard about it happening, but that doesn't mean it couldn't happen).

Using half laps, the ends in the lap would only be 3/8" thick, and that's a negligible thickness for any movement to happen. It would be unlikely IMO. Half laps are easy to do. I use them quite often.

In using a dowel or series of dowels or M&T, the possibility of being off slightly demeans the joint.

If you want to eliminate any concerns for movement, cut the bottom rail out of 3/4" Oak plywood. Add 1/4" solid wood to the long edges, and then use that as you would a solid piece of wood. For that matter all the members in the frame could be done that way.

As for mounting the mirror, rabbet the back to accept the mirror. A thin bead of clear silicone to hold the mirror in place would also make the frame more rigid and would help in minimizing the possibility of joint separation.
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[SARGE..g-47]

If you go back and look at the picture in the plan.. you see this has only 4 components less the glass for the center. All 4 have an open side to expand to as wood will indeed expand cross grain much more than long grain. Having 4 sides that will allow expansion.. basically narrow components.. wood properly dried and then acclimated to the shop before you start.. coats of finish applied after joinery....

With that said... I personally wouldn't give a second thought to this relatively small piece gaining or losing enough significant moisture to allow enough expansion or contraction to split a component or over-power a joint.

Good luck...

[Lonnie in Orlando]

Position and wire the frame hangers to relieve stress on the joints. Here is one way ...

> Attach the picture wire to frame hanger #1 at the bottom corner of the frame.
> Run the wire thru frame hanger #2 near the top of the frame on the opposite stile.
> Leave slack for the wire to hang onto one or two wall hangers.
> Run the wire through frame hanger #3 opposite frame hanger #2.
> Attach the wire to frame hanger #4 at the bottom of the frame opposite frame hanger #1.

This will support the mirror from the bottom and will pull the corners together.

- Lonnie

[LarryG]

Using half laps, the ends in the lap would only be 3/8" thick, and that's a negligible thickness for any movement to happen. It would be unlikely IMO.

That is simply incorrect, and I am stunned than someone who claims to be a professional woodworker would say such a thing. Wood of ANY thickness will expand and contract across its grain. Many a panel-type door has been built using a 1/4" panel made of solid wood, and they are typically not glued to the stiles and rails precisely because they need to be able to move.

[schloff]

How about pegged half-laps, Greene & Greene style?

Exactly. This is what I used for the door of a large corner cabinet. Very strong, heavy, and attractive. 1/2" oak dowels on end contrasts to the face grain of the door.

[cabinetman]

That is simply incorrect, and I am stunned than someone who claims to be a professional woodworker would say such a thing. Wood of ANY thickness will expand and contract across its grain. Many a panel-type door has been built using a 1/4" panel made of solid wood, and they are typically not glued to the stiles and rails precisely because they need to be able to move.

I'm not surprised that you're stunned. In doing the work judgments are made as to viability of the process at hand. Having done this process I relate the process. Maybe I just get lucky. I wouldn't do cabinet doors with 1/4" solid wood panels, nor would other professional woodworkers, IMO.
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[LarryG]

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[cabinetman]

I'm not surprised that you're stunned. In doing the work judgments are made as to viability of the process at hand. Having done this process I relate the process.

Uh ... what? I have no idea what you are trying to say there.

In simple terms, when the work is being done, a decision on the joinery is made. Having done this procedure, I responded with the decision regarding the joinery.
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[LarryG]

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[cabinetman]

That still doesn't make sense, but moving on ...

Earlier you wrote, "I wouldn't do cabinet doors with 1/4" solid wood panels, nor would other professional woodworkers, IMO." Those comments don't directly address what I wrote, but I presume you mean most people would consider a panel only 1/4" thick to feel a bit cheap and flimsy. I'll go along with that (although the fact remains that many doors have been built exactly that way, including quite a few by professional woodworkers).

So let's instead consider a typical raised panel that is 3/4" thick but reduced on its edges to 1/4" to fit into a groove in the stiles and rails. If your contention that wood that is 3/8" thick won't expand or contract enough to matter were correct, couldn't a panel that is 1/4" thick at its edges be glued into place rather than being left free to float?

I'd also like to know why you say you're not surprised I'm stunned.

Instead of hijacking this thread any further, PM me and I'll answer all your questions.
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[just started]

You could also be different and use a box joint or maybe some of those fancy rounded dovetails to hold the rails and stiles together.

[Stytooner]

I will say that there hasn't been a joint mentioned in this thread that I haven't used with success. There are others that haven't been mentioned. Loose M&T, through M&T, through screws plugged with dowels, pinned, pegged splines, biscuits, L-bracket backed, a sliding dovetail, corrugated nails and just a plain old butt joint. And this is just a few of the possibilities.
With today's glues, most joinery will be mainly for aesthetics first and strength second. You only need a strong joint in the event of glue failure. On butt joints alone, wood failure is also a possibility and would be why it really should not be used to carry a load, but would be suitable to contain a small picture or used as a face frame. That way a failure isn't as dramatic and can often be repaired.

Choosing which joint you use has more to do with what you want to accomplish and ultimately see in the piece. You have to consider end usage, location and what tools you actually have and your own personal experience making and using things with the chosen joint.

Lonnie's hanging method also has a lot of merit and would put the load on the bottom rail mainly. Simply a good idea.

I will say too that in my experience with cabinets, it was wide rail cathedral style doors that failed the most often. I probably saw it about a dozen times.
These were all double doweled. The joints did not completely fail, but did crack open and likely every one due to humidity in new construction locations where the home was still unoccupied and unfinished. We never had it occur on remodels or homes that were more complete. Because of this, we would install all the boxes first and not install cabinet doors until the house was enclosed and the AC was working.

So you can do easy to hard and great looking to unseen and fast to time consuming joinery. The choice is up to you. The more familiar you are with different types of joints, the easier it is to choose which one you can do best and which would look the best. Personal choices from the start.
Good luck with it and post some pictures when you git er dun.

[JimD]

I agree that this project is relatively low stress and lots of joints will work fine including dowels. Mirrors do not open and close like doors which helps keep the stress low.

The low stress could also be a reason to try mortise and tenon again, however. I never got decent results with drilling and chiseling either. I get good results with both plunge router making the mortise and with my hollow chisel mortiser. You probably do not have a hollow chisel mortiser but I'm guessing you have a plunge router. If not, then dowels or just pocket screws will work.

With a plunge router, you need either an up spiral cutting bit or a straight bit with an extra cutter on the bottom so it can cut it's own hole. The latter is less expensive. The most fool proof way to cut the mortise is to make a little jig and use a template guide, woodsmith had an excellant instuction piece for this. You can also just use a guide like you would use for cutting dados on big pieces.

Jim

[drumpriest]

I always love pointing out this bit on the tutorials section, as many people never realize that there even IS a tutorial section, but here ya go.

http://bt3central.com/showthread.php?t=27419

I would think the dowels would be fine in this application. If wood movement is an issue at 7+ inches where you are, there are ways to deal with that situation. Glue only the top 3" or so, and using pocket screws for the lower is an example of that. Pocket screws pivot a bit and allow for some movement to occur.

oversized mortises and a lower pegged tenon (no glue, tenon is smaller than the mortise) allows for movement and is pretty swanky. (yep, I said that)

[gsmittle]

That still doesn't make sense, but moving on ...

I'd also like to know why you say you're not surprised I'm stunned.

Gentlemen, let's keep it civil. We can read all the flame wars we want elsewhere.

g.