Summary

This design was inspired by my earlier Shark Wrench (Poseidon's Pet).

This toy prints well in PLA and ABS. I have printed it successfully at 75% scale (~18cm) and 100% scale (~27cm). Printing it less than 75% may be difficult as the gears might lose fidelity. If you do get successful prints that are less than 75% scale please let me know.

I print the Gear Screw and Abdomen Gear at low speeds.

Assembly requires a screw and preferably a washer.

Drill a hole through the abdomen gear and the crank that allows your screw to spin freely (look for guide holes). Drill a smaller diameter pilot hole in the middle of the body (flat portion, look for guide hole) to ensure that plastic will not split, but will hold screw snuggly.

When screwing the Gear Shroud to the Body, make sure the Abdomen Gear is seated properly in the Gear Shroud, and that the Crank is seated properly behind the Gear Shroud and locked properly to the Abdomen Gear.

The Gear Shroud has a threaded connection to the Skull (like a jar lid). Tighten the Gear Shroud as loose as possible while making sure that it is tight enough to turn the Gear Screw. Over tightening may break the Gear Screw. A little white grease on Gear Screw will help to make the jaw movement smoother.

The Jaw is printed in two pieces (Jaw and Jaw Screw). They fit together by means of a Dovetail connection. It is fairly snug (no glue required).

This toy had a lot of design changes. It cost me many months and a few spools of filament. In the end, I think it was worth it. It looks pretty good, and gets a lot of compliments.

To see the DevilFish in action, and how to assemble you can check out this video.
https://youtu.be/7hATmZmMOy0

Special thanks to Thanks to Dan Kirshner for Thread Library and Jeremy Green for the Dovetail library.

I have also include the OpenSCAD file if anyone is interested.