I had a go at cutting a 30T HTD pulley on the router yesterday. I used a 3.1mm drill to make holes to match the profile of the teeth, then milled the profile using a 1/8" carbide cutter. Since the maximum tool diameter which can cut this profile is 3mm, the 1/8" cutter only reaches near the corners, but it still left a good profile which fitted the belt admirably first time:

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The holes were a bit rough, even with the flood coolant, so I may try a carbide drill or maybe mill the entire profile. The issue with milling the entire profile is the required cutter is very long and thin, so it would be slow unless I use the 4th axis as I have previously for XL pulleys.

Here's a video:



It would be entertaining to try cutting a non-circular pulley, so the driven pulley rotation would be some arbitrary function of the other pulley position, not just a simple ratio. Might be useful for something...