Finger Biting Toy

The Classic Toy That Bites!

**Based on people's feedback, it is still not a very stable version. Please use PETG (PLA is too fragile) and dry the spool as it was printed OK for me.  The cam rotation piece needs to be glued together before use. The insert on the shaft is for alignment only as it cannot handle the force.

Although I went through many many iterations and reinforce various parts that broke for me during assembly, seems some of the parts still tend to break for people when force used. Thanks a lot for the comments/advises from the comment section. I will find time addressing those issues.**

Push one of the teeth, and with a 1 in 10 chance, the cute little shark will bite your finger! Each round, the trigger tooth is completely random, making every playthrough a surprise!

I’ve always been curious about how this toy sets a “random” tooth as the trigger for each round. After spending countless hours modeling it from scratch, I’m still amazed by the ingenuity of the mechanism. It’s not only a fun toy but also a fascinating lesson in engineering.

Assemble instruction:

Step 1: Begin by assembling the different pieces onto the base as shown in the video. Make sure that the "rotating piece with two blades" can rotate freely. If the smaller threaded pillar inserted into the base tends to fall out easily, you may want to glue it in place.

Step 2: Assemble the cam rotation piece. This consists of four parts. The inner pillar provides strength (printed horizontally), and the outer shell prints smooth surface for rotation. Pay attention to the left and right orientation of the two outer pillar shells—the left pillar has a shorter insert. Also, check the direction of the middle piece. Once properly aligned, glue the left and right pieces onto the middle part. (Make sure it is correctly assembled before glue!)

Step 3. Assemble the 10 individual teeth.

Step 4. Install the remaining pieces (plate under teeth, upper teeth, etc.)

Step 5. Place the entire structure into the cute shark shell.

Important notes:

The mechanism of this toy requires some precision, so it might not work perfectly right out of the box, or you may face some assembly challenges. Here are some additional tips:

1. Accuracy of the Plates: Make sure the second plate (the one that moves slightly up and down and latches onto the rear part of the base) has the correct measurements for its latches. The image below shows a version with too small a diameter, printed poorly by the printer. The diameter should be between 4.6mm and 4.8mm.

2. Assembly Force: Some pieces may require a little extra force to assemble. If you break a piece, don’t worry—use super glue to reattach it. After a couple of hours, the super glue will be stronger than the filament itself. Note that the cam rotation piece requires glue, but all other pieces do not.
3. Rectangular Nut: Do not over-tighten the rectangular nut, as this can cause the pieces underneath it to stick too closely together.