We have a Combind C20 book binding machine at work that uses those plastic comb rings. It notches rectanglular holes in the side of all your sheets then you feed them into the combs.

The handle on the comb opener broke off a long time ago and we have been using some small vice grips, but I finally got around to designing a replacement handle.

You will need a 10/24 set screw for best results, 3/8 long or less is probably fine.

Edit: I made a revised version with a longer handle and also angled the square drive to maximize the leverage!

Edit: Remade again, adjusted the length a bit more and then shifted the square offset further. This is now a perfect fit for the machine. Removed old versions.

Snapmaker 2 A350

No

Doesn't Matter

.08

100

I am sure you can use any type of plastic you want. I used petg because i expect it to hold up better than PLA. I am sure it doesn't need to be 100% infill but even on high quality (recommended from the threads even though you could just tap it) it is about 1 hour 40 minute print.