Hi Vic not quite point and press I use one of these bit more permanent    link

Tachometer 4 Digital LED Tach RPM Speed Meter + Hall Proximity Switch Sensor NPN

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I bought the exact same digital tachometer as in the photos th check the Tom senior with the VFD and three phase motor for the most useful speed range, which turned out to be from using the four belt speeds combined with 25-75 Hz settings. The Atlas lathe got tested the other week to find what the total range was.

High range : 2050,   1272,   819,  525

Low range : 952,   584,   375,  240

High back gear :345,   212,   136,   87

Low back gear : 158,   97,   62,   39

Notice that the uneven spacing which makes having 16 speeds less useful.

Smart & Brown got the speed spacing exactly right with the model A’s 12 speeds from 39 to 1440

If your lathe has a 60 tooth gear then you can make up a little printed circuit together with a tiny magnet and segment display have a permanent rpm read out. There has been several very good articles in ME and MEW in the passed, one I remember, used VW car inti skid sensor to count the teeth on the super 7 bull wheel.

I bought the same unit a while back to adjust the minimum speed on a router.