Older people often have troubles opening plastic bottles. Also, people with gout or other disabilities lack the required strength to turn the small caps independently. The reason is the small diameter of the caps, which requires a strong grip with just two fingers.
There exist a variety of helper tools, assisting this task by increasing the leverage. A common problem with these tools is the static design. So if the manufacturer changes the size of the bottle cap, they do not grip properly anymore.
My design uses a tapered hole with 72 teeth. This hole slides over the cap and, with no or little pressure, grips the cap securely. The taper will allow a capsize variation of ±1mm.
At the outside, I added eight round notches, so the fingers of one hand can securely grab the tool.
I created STL files for three different cap sizes: 26, 28 and 30mm diameter caps.
The design was made for caps like the one shown above. Most of the caps I checked had a 72 teeth design and were in the range of 26-30mm diameter.
Because of the torque forces, you need to use a tough material like PETG. Print with 30% infill and four perimeter layers.
There are no supports required. Print it with the handle side on the printer bed.
Download the STL files here:
LR2142 Bottle Opener by Lucky Resistor is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
The Fusion360 design is available for my Patreons.
I hope you find this design useful. There were a limited number of water bottles I could test, so if it doesn’t work for you, please send a closeup picture of the cap with all dimensions. I will then try to adapt the design to this cap.