Quick question that came up while I was tuning a 20° pressure-angle spur pair in a compact gearbox: was involute’s big win truly its constant velocity under sloppy center distance, or did manufacturing simplicity seal the deal? If you’ve got a historical nugget — or a consumer example where that forgiveness directly improved user experience (think snap-fit gear trains) — I’d love to hear it.
Center-distance forgiveness won it; the rack-form hob just made it cheap to scale. > a consumer example where that forgiveness directly improved user experience (think snap-fit gear trains) — I’d In cheap inkjet paper-feed trains and wind-up toys, clip-fit bosses wander and housings warp, yet involute keeps ratio and runs quiet; if noise is your constraint in that compact 20° pair, try a small +0.05–0.1 profile shift and compare.
In cheap injection‑molded spur trains — RC toys and hobby servos — what saves the day isn’t just “constant velocity with mis‑set centers” but also easy profile shift on involutes, so you can beef up a 10–12T pinion without undercut and still keep the same mold spacing. @olivia_carter2005 is right on hobbing; the UX win is you can snap the case together and it won’t bind (like jeans after the dryer) — got a real-world case where cycloidal beat it outside watches?