This is one of those things that started out as one way and then literally (you'll get it later) went the other direction.

My printer has a 8mm shaft with pulleys driving the Y axiz its a BIG gantry so two belts to keep it true I've had a geared drive on there for months and it works 100% but I felt its was a little noisy so I thought maybe as it printing quality is better than it was before I should redo the drive. I had originally made it to run with the herringbone gears as attached ( they are from a herringbone extruder that I modified from taking a hobbed bolt to a shaft) The herringbone gears are very particular about the messing of teeth and proved difficult. I had a few printed spur gears that I ended up using and that was what was on there for probably 7-8 months.

For this I redesigned the holder. It takes a Nema17 motor and the attached herringbone gears will go in. You will need to ass a 608z bearing for the shaft its a bit of a push fit but sits nicely. The gears where still noisy and any imperfection in the gears had a tendency to catch. So I binned the idea and decided to try with a belt drive. a little more forgiving of tolerance and after printing a t2,5 that works well enough to make the aluminum pulley I got to replace it sit on my desk as spares I thought I would give a T2 gear a go

After about 10 prints I finally had one that works well. I had to size it and added teeth till the belt fit snugly. You will also need to invert the motor in the firmware as it goes in the same direction as the motor not opposite as it does with gears. (get it now :-)

It works well and is much quieter, steps reduce from the gear setup. It wont be something many would need but maybe there is someone who needs this to get their setup working.

If you want to see more and how I create prints and 3D designs like this check out my YouTube channel.
https://www.youtube.com/channel/UCSHUc93NXGwBacoIDDqPU2w

The herringbone gears dont need to be printed they are included as they where part of the original design.

You will need a drive pulley for the motor T2 to match the driven pulley Think mine is a 20t You will need a small t2 belt (ultimaker)
You will need a 608z bearing for the shaft and you're on your own for a holder for the other side of the shaft but essentially something to hold another bearing in place.

There are different screw holes you can pick what you need.