Introduction: Mini Knuckle Slingshot

About: Hi I'm Michael! I love all things Science, Engineering, & 3D Printing. If you've enjoyed my work then I've love to hear from you!

While the ultimate minimalist slingshot design is to just use a rubber band and two fingers, it is difficult to get a good shot that way. The design intent of this project was to create the 'smallest slingshot that you'd actually want to use'.

This device works really well despite its small size because when you straighten your elbow and lock your arm everything is held super steady and the shot lines up with your forearm, and it prevents you from accidentally blasting yourself in the finger too. Your thumb is not needed to hold it so you can keep it out of the way.

I've seen a lot of creative slingshots out there but not one quite like this. In any case the 3d printed TPU pouch works wonderfully as an easy alternative to handmade leather.

The rubber bands were sold at the hardware store as 'trash can rubber bands' and were meant to hold trash bags around your can. They are some sort of synthetic rubber so it doesn't dry out. And they are just the right length.
The rubber bands we used:

Our TPU filament of choice:

Step 1: 3D Printing Settings

PLA Frame- 0.2mm layers, 5 perimeters, 25% infill. (So basically printed solid, this design is not the occasion to save plastic!)

TPU pouch- It's so thin that any settings render it completely solid which is fine.


*XL-23.5mm Dia index, 24.5mm middle finger

*MED- 21.5mm Dia index, 22.5mm middle finger (my size, adult man, 6ft, lean)

*SML- 17mm Dia index, 18mm middle finger

Step 2: Wrap Band on Pouch First

Rubber band wrapping, there are only two ways to do it without cutting the band, but one is better than the other. See images which show how to wrap the band so it wants to keep the pouch on center.

Step 3: Wrap Band on Frame Second

Use the images for reference on the intended wrapping method. Basically through the hole first then wrap around and pull tight so the rubber band keeps itself in place while still being replaceable if you wanted.

Step 4: Play -Safely-

I experimented with different pouch designs and learned exactly why you want the pouch to be flexible...

If you use a hard cup shape it will support the shot too much and it can veer off uncontrollably. Because of this I broke my laptop monitor with a marble while experimenting...! Ugh. The flexible pouch allows the rubber bands to pull the shot toward the center and prevents this. Even so I recommend using mini marshmallows when shooting in the house or with kids.

Also make sure to choose the right frame size for your fingers and hold it as shown. Having a firm fit is critical to keeping the tool steady. Have fun and if you enjoyed this project please take a moment to vote for it in the Pocket Sized Contest thanks!

Pocket-Sized Speed Challenge

Participated in the
Pocket-Sized Speed Challenge