For the past few weeks I’ve been teaching myself how to use Fusion 360, a free online cloud-based CAD/CAM program that lets you create your own 3D designs. The best way to learn how to use a new program is to build something you actually need. And my latest design is a work in progress that I think is not just something I need, but something that would be quite useful for many other people with 3D printers.
On my Goodman ZONE camera the lens is held in place using four M4 hex socket cap screws. The hex socket caps, also known as Inbus or Allen sockets, can only be loosened or tightened using a properly sized hex key. The big problem with hex keys is that while it’s a common tool, it’s also one that you rarely have with you – especially when you don’t know you need one beforehand. For the ZONE camera I often found myself in the situation that I couldn’t replace or tighten the lens on my camera when I was out shooting and didn’t bring the right hex key.
To remedy this problem, I’ve designed these little knob caps that can be 3D-printed and perfectly fit onto your M4 hex socket caps, making them into knurled thumbscrews instead. The internal hex-shaped protrusion of the knob functions as a driver and helps turn your screw the same way a hex key would. The exterior surface of the knob is larger and knurled to give your fingers something to grip. The knob is 0.5mm shorter than the screw head, so it will not damage the surface of an object you screw it into.
Hex screws without knob caps… 
… and with knob caps
With these caps fitted onto the hex socket screws I’ve converted them to knurled thumbscrews, allowing me to switch lenses on the ZONE on-the-go without a hex key. This works remarkably well, but always remember that you’re working with 3D-printed plastic. Don’t expect wonders and don’t use excessive force tightening the screws.
You can download my design on Thingiverse. I may make a few more sizes of these – my Goodman camera also needs M3 caps, so that would be a logical next choice!