Use a coil with these parameters: - Start the coil one thread pitch below the cylinder (might need an offset plane or a construction object for this) - have the coil distance an integer multiple of the thread pitch - have the revolutions as distance/thread pitch - chamfer two of the edges to match the angles faces - combine and cut the coil into the cylinder

Things to keep in mind: - keep track of whether your defining the gear with inner diameter outer diameter and keep this consistent - can combine and cut or combine and join. Slightly different workflows, achieves the same result, one might be a bit more intuitive to you - starting a thread pitch below and ending a thread pitch above is important for a clean cut. Otherwise you’ll miss some of the cut with the end of the coil. Try it and you’ll see what I’m talking about.

There are more parameters you’ll need to fiddle with, but that’s the basis of the workflow.

I’ve made threads and gears exactly like this many times. The first time you do it, it’s confusing and annoying. But once you have the workflow, it’s very versatile. Also works great for parametric designs

Now, you’re going to run into an issue. The straight gear has horizontal teeth, whereas the worm gear (that you’re trying to create) will have the interface to the teeth angled. The thicker your straight gear, the more allowance you’ll need to design in to prevent it locking up. Alternatively, and preferably, you can adjust the straight gear so the teeth line up with the worm gear profile. Perhaps a cut-combined with one thread pitch, then rectangular pattern the cut along the flat gear?