The stroboscope wheel I made covers most lathe speed ranges. To use, save the file to your computer and print to fit a letter size sheet of paper. The disc will work at any size, just make sure it fits the swing of your lathe. I recommend cutting a wood disc on your lathe, cutting out the paper disc and then gluing paper to wood, center best you can.
Strobe tach disc (provided below)
Wood to mount the paper disc
60hz fluorescent light or stroboscope
Direct link: http://i.imgur.com/1aX6gx7.jpg
2017 Update, this new color version makes it easier to distinguish bands.
Video of wheel in action and explanation of how it works.
Still of disc in action:
The goal was to accomplish this: each # on the tape represents a band on the tach wheel.
So I could make this
If you want to make your own strobe tach disc from scratch, here is the math. Neither the length of the bars nor the distance between them matter, all that matters is they are equally spaced. Rather than make a circle, you can make them in a line and glue it around the outside edge of a wood circle.
Formula: 120 x hz/rpm = equally spaced bars or 120 x hz/bars = rpm
So to make a strobe disc for 480 rpm in the US (60Hz)
120×60/480= 15 bars equally spaced
120×50/480= 12.5 bars (doesn’t work out evenly so we’ll adjust the formula to work with whole bars)
120×50/13 (bars)= 461.5 RPMs (fraction)
120×50/12 (bars)= 500 RPMs (nice even #)