I had need to basically slice apart my frame that I was making.
I wanted to create as much surface area as possible for the pvc glue to
take hold.

So Instead of just creating 2 cubes to glue together I made a set of
dovetail cubes.

I figured that any way that gets the job done is a good way (like any
landing you walk away from is a good landing sort of thing).

But, since I have not been doing this too long. And am only part time at
it, I would ask if there was a better way I could have done what I did, or
would most people have done something similar?

Anyway, here is the code:

// dovetail cubes: a male that fits into a female

// in the following two modules:
//  w = width of cubes
//  l = the length of the cubes
//  t = the thickness

module malecube(w=4, l=5, t=1) {
translate([0,0,-l/2]) cube([t,w,l], center=true);
translate([-t0.5,w/2,0]) rotate([90,0,0]) linear_extrude(height=w)
polygon(
points=[[0,0],[t0.5,t*0.5],[t,0]]
);
}

module femalecube(w=4, l=5, t=1) {
difference() {
cube([t,w,l], center=true);
translate([-t/2,w/2+0.1,-l/2-0.01])
rotate([90,0,0]) linear_extrude(height=w+0.2)
polygon(
points=[[0,0],[t0.5,t0.5],[t,0]]
);
}
}

// tests:
//translate([0,0,0]) femalecube(14, 14, 6);
//translate([0,0,-15]) malecube(14, 10, 6);

--
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The most exciting phrase to hear in science - the one that heralds new
discoveries - is not "Eureka!" but "That's funny...".- Isaac. Asimov

I
*f you give someone a program, you will frustrate them for a day; if you
teach them how to program, you will frustrate them for a lifetime. *-
Anonymous

If writing good code requires very little comments, then writing really
excellent code requires no comments at all!- Ken Thompson

Looks OK to me - lots of ways to skin a cat (what an awful expression!) with
Openscad.

I'd be tempted to remove redundancy by defining the female in terms of the
male e.g

module femalecube(w,l,t) {
difference() {
translate([0,0,l/2]) cube([t,w,l],center=true);
malecube(w,l,t);
}
}

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Remember you may need a little bit of clearance, so they will slide together
without forcing out all of the glue.

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Tongue and groove is a joint intended to not-be-glued, as it makes for  poor
joint strength in tensile loading across the joint, but good strength
without glueing transverse to the tongue. Wood joints have in the past been
developed with the properties of hide glue in mind, and that means a very
brittle joint that cracks easily along the joint line. Luthiers use this
brittleness on purpose; when they need to open e.g. a violin for repairs, a
slight hit with a hammer on a glue line will separate  the top plate from
the carcass without damaging the wood, try that with a more modern glue such
as PVA (white glue).
Since the PVC glueyou want to use is rather brittle when dry, and because it
shrinks while the solvent evaporates, a tongue-and-groove joint with play
between tongue and groove would be a weak joint as it is susceptible to
impact failure. If you can, use a tapered joint, such as this:
http://forum.openscad.org/file/n13946/Taper_Joint.jpg
and clamp firmly until the glue has set. There is no need to slavishly
follow this design, all that is needed is that the long sides of the taper
are 5-10 times the dimension of the short side to make a joint at least as
strong as the base material. I have built masts that way for wooden sailing
boats. The example picture is from a commercial wood joint, where knot-free
wood has been created by cutting out the knots, and jointing the remainder
with minimum loss of material.

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Hi wolf, very helpful tips. Do you have a blog ?

$  Runsun Pan, PhD

$ -- libs: doctest , faces ( git ), offliner ( git );

tips: hash( 1 , 2 ), sweep , var , lerp

$ -- Linux Mint 17.1 Rebecca x64  + OpenSCAD 2015.03.15/2015.04.01.nightly

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Sorry, Runsun, no blog. One of the applications of tongue and groove is in
floor boards, which are nailed to the substrate and where the tongue and
groove's key purpose is to suppress warping. But parquet is glued, using
either a latex (rubber) or bitumen based glue, with enough mineral filler
added that it can bridge 1 or 2 mm gaps, and therefor not tongue and
grooved. But Laminated Flooring has a "click-on" edge, a variant of tongue
and groove, that permits the boards to keep together without nailing or
glueing. Laminated Flooring just free-floats on a thin mat of styrofoam.

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