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Mini-Lathe 100 TPI Stacked Change Gear
Before turning the PVC conduit to the proper diameter for the Shopvac hose adapter, I set up a 20-50-32-80 change gear train for a 100 TPI finish. While the urethane adhesive cured in the hose, I fed the BC gear pair into my change gear generator:

Mini-lathe stacked change gears – 32-50T – solid model It’s ready for the next time I cut something down to size:

Mini-lathe 100 TPI change gears One reference suggests a 256 TPI finish for “general turning”, which works out to 20-80-20-80:

Mini-lathe stacked change gears – 20-80T – solid model That’s just crazy talk, because the BC washer overlaps the D gear teeth:

Mini-lathe 256 TPI change gears If all else fails and I really need a 256 TPI finish, lathes are pretty good at making washers.