Well, I tried to ask nicely, but Primex told me to pound sand.

So what is the difference between a 12 hour and a 24 hour clock movement anyway? Well, clearly the gear ratio between the minute and second hand is twice as slow. But what does that physically mean?

Here's a 12 hour movement on the left, 24 hour on the right. Notice two of the gears are grey on the 24 hour movement. Those are the two gears that transmit the minute hand movement to the hour hand. Cutting to the chase, it turns out that nothing else is different, and simply moving the two grey gears over to replace their counterparts on the 12 hour movement work just fine.

Well, can we 3D print those two grey gears?

First, if I am even going to attempt it, let me say at the outset that I am glad I have a Form 3. I have serious doubts that any FDM printer would have any sort of shot at it. SLA may not even be good enough. I may have to get these done via SLS at Shapeways.

But first thing's first. I have to model them in Fusion 360. I've never attempted anything this critical before.

Time to get out the calipers...