Inexpensive DIY tachometer for a mill or lathe

Here’s an idea I haven’t seen before.  Adam made a very inexpensive tachometer for his variable speed X2 mini-mill using a cyclometer (bicycle speedometer).  Almost any wired cyclometer will work and you should be able find one with a nice big display for about $15 or less.   (You probably don’t want to get a wireless cyclometer because they’re more expensive, you’ll have an extra battery to replace occasionally, and you might get erroneous readings caused by the receiver picking up electrical noise from your motor).… Read the rest