Small Hex/Torx bit handle

Designed for finger tightening of bike water bottle cage bolts, which don't need to be anything more than finger tight, and are often annoyingly hard to get at. Inspired by several different models out there, but mostly by this one: https://www.printables.com/model/40361-hex-driver-key-updated-19042022

The hex hole is deliberately undersized, at 6.15mm flat-flat. All the hex key bits I have on hand measure 6.25-6.30mm flat-flat. My intention is for the handle to be printed in PLA, and for the bit to be “heat set” in the handle. This way the handle is manually molded to the bit, and holds it quite snug. This still allows the bit to be pulled out with a pair of pliers, but won't allow it to fall out. 

Intended to be printed in PLA. 0.15mm layer height @ 25% infill works great.

To heat-set the bit:

1. put the electric kettle on (or heat some water to just below a boil), and get a small bowl that's suitable for hot liquids. 
2. You'll have to work quickly to complete the next few steps, but you can always start over at step 3. You have more than one shot to get this right.
3. Pour the hot water in the bowl, soak the handle in the bowl for ~10 seconds, and then fish the handle out (wear heat resistant, non absorbent gloves unless you have chef hands!). 
4. With the handle sitting on a counter, hole facing up, push the bit into the now malleable handle. 
5. If cool enough to touch, use four fingers to press on the cylinder and push the plastic against the bit as it cools. 
6. Leaving the bit in the handle, repeat the process as needed until you're satisfied with the grip the handle has on the bit. This usually only takes 2 soakings in hot water, and the water will still be hot enough to soften the PLA for a few minutes.
7. When satisfied, wash or dunk the bit & handle in cold water to harden the plastic. It will take several minutes for the inside of the handle to fully harden in air, so feel free to leave it in cold water to speed up the process.
8. The cylinder of the handle will have deformed slightly in the process, but this lets you know that the bit is a real tight fit. When you pull then bit out, you should hear a nice suction pop!
9. Print more handles for all your bits! Bonus points if you have enough filament colors to print each size a different color, in some type of coherent color order, like a rainbow!