Hi Brain,
Last March I published a HMT article about a Hall effect tachometer for a 12" swing geared-head lathe built in Taiwan in the late 1980's. The speeds on the speed select plates were never exactly correct. Randy Richard thought my lathe was originally designed for 50HZ motors because he had a similar incorrect speed issue with his foreign built lathe. I no longer notice the speed differences now that I have gotten use to using my lathe but I is still handy to look at the tach to remind me which speed I am using.
Thanks for the video, Paul