Simple Strobe Tach

I used that with a neon "night light" before I bought a proper tachometer. I used a highlighter to colour the band of prime interest for greater ease in locating it in the dim lighting. Gerry :-)} London, Canada

Yeah, I still don't own a tach, other than one of those non-contacting electrostatic pickup ones used for checking the speed of one cylinder gas engines.

But, when I was curious about what the actual spindle speeds on my old Stark lathe were after I'd bought it and fitted it up with a step V-belt pully and a Craftsman speed change pully rig made for use with wood lathes, I did this:

I securely taped a small magnet on the inside of one of the chuck jaws, hooked an old relay coil across the input of my oscilloscope, held the coil near the spinning chuck, measured the pulse spacing with the scope's time base, and did the math.

Pretty is as pretty does.....

Jeff

PS- Here's my Stark lathe:

That rectangular tag hanging off a hook to the left of the chuck is a gage I made equal to the didtance between the top of the cross slide and the spindle centerline. I makes for easy setting of a tool bit in the lantern toolpost.