Got my digital tach yesterday and decided to see what I could do with it last night. First..I had to stack 4 6 mm x 3mm..neodymium magnets together and glue them to the spindle so they would stick out far enough for the sensor to pick up as it passed. Made a small bracket out of sheet metal for the sensor. I may end up moving it to the tail end of the spindle because the magnets like to collect swarf. I tested it with my lathe on low gear which is supposed to be 0-1100...the pictures show my readings I got at idle and fullspeed. Anyway..this was a quick throw together to see if it worked...
