If you do not need a continuous speed reading, one solution would one of those relatively inexpensive, hand held, laser units with digital readout.? I believe the counter within is crystal controlled, so the accuracy should be in the 0.01% region.? These meters come with a supply of reflective tape.? You just place a narrow strip on a chuck or the like and point the laser beam while the machine is running.? An advantage is that you can use it on any number of machines and for such things as setting the idle speed of your automobile engine.?
I bought mine to measure the chuck speed of a micro drill press I was making and wanted to be able to read up to 25,000 RPM.? It worked fine.? This was about ten years ago.? I do not know what these units currently cost, but I think I paid about $28.
Bruce
ebrucehunter