i do think its kind of demonstrative as to how the geometry of blades work to look at a macuahuitl and how it's constructed - chances are you've seen a reconstruction that looks a bit like this
now first of all im not sure whats going on with those microliths (small stone tool - in this case a blade. obsidian counts) because they look trash (machined, doesnt really work with obsidian) but that's not the point it's basically a club. ye olde baseball bat with nails in it. now we all probably could've guessed that this was wrong, just based on firsthand accounts - mostly the ones about them cutting straight through a horses neck, which this above weapon profile likely could not do. period maccuahuimeh (i think thats the plural) have been bouncing around for centuries, but because of poor european standards of archaeological providence theyve been put in the wrong collections or ignored, making a lot of info not particularly up to snuff (some ended up in the japanese section of a madrid museum, i think, which perished in a fire). anyway luckily there is a piece in the museo del templo mayor that was found in mexico city
now obviously the blades are quite thin and were set long-ways, and heres an image from the aforementioned pieces in Madrid (the second is a tepoztopilli, demonstrates that they made other blades like this)
The blades seem to be flush with each other. Looking at some other photos of the San Marcos example (it was found on San Marcos street)
note: probably wasn't curved like that when it was manufactured originally, but it was in the ground for centuries so warped a bit. you can understand the pressure she was under
you can see the groove is uninterrupted, meaning it seems likely they were flush based on this too, as if they were set with spaces between the blades a continuous groove would probably introduce some structural instability for no real reason. We can also see based on both examples that it's slightly angled, and very smooth, and alongside with the adhesive filling a bit of the gap the geometry would be conducive to cutting - and heres some diagrams of the way blade geometry works
(this one is mine - can you tell?)
without that nice angle, the force wouldn't be concentrated on the edge, and since blunt wood doesn't cut well, the weapon wouldn't either. the centre steel and wood (A) isnt doing any cutting work, but its guiding the medium (labelled meat) such that the edge can keep contact and alignment, and angled so it doesnt get caught and stop short. That's why a lot of bladesmithing traditions use a slightly different steel for the edge and for the middle or blunt end, because you need slightly different things to keep the blade structurally sound and actually hold an edge. the same basic principle is used when it's wood and obsidian.
and at the end of the day, that's why spanish accounts of the conquest say "yeah, they had swords, just made of obsidian and wood instead of steel, wicked sharp" and why they're swords. they were cutting weapons. and that's why edge alignment matters, even beyond the initial cut, because you need the blade to keep cutting. the Mexica did use clubs, but these were not clubs.
(There's probably other examples either in private storage, or in various Mexican museums, and I don't know any Spanish so I can't really say, but if you do know Mexican spanish well enough maybe take a look at some catalogues, and let me know if you find anything. This one is on public display though, thanks be to the good people at the museo del templo mayor.)
alright for the second and third photos of the San Marcos macuahuitl, theyre attributed to the illustrator/archaeologist Rafael Mena, but I found them on a korean-language furry's history blog, and couldn't find them on Mena's profile, since twitter's search sucks. Just for providence's sake.
also, Dr. Juana Moreno Hernandez, the archaeologist who dug up the San Marcos macuahuitl, did a presentation on it on youtube! I might see if I can get through it just with the machine translation (the future is amazing), but theres a lot of photos there too. Here it is :)
thanks you dr. hernandez for the wonderful sword