While sorting through some old tools and equipment, I came across this curious device — compact, mechanical, and clearly built to last. It’s got a dial, some numbers, and what looks like a spindle or tip that might connect to moving parts. The craftsmanship hints that it’s from a time when precision tools were mostly analog, not digital.
After a bit of research, I discovered this is an old RPM counter, sometimes called a tachometer. It was used to measure the speed of rotating parts — things like engine shafts, pulleys, or machinery spindles.
How It Worked
The pointed tip or rubber adapter would be pressed against the rotating shaft or pulley. As the part spun, the counter inside the device would record the number of revolutions per minute (RPM). Some versions even had small gears or dials to display precise readings.
Before digital sensors became common, mechanics and engineers relied on these handheld tools to tune engines, test machine speeds, or ensure equipment was running within safe limits.
A Glimpse into Mechanical History
Holding one of these in your hand is like holding a piece of industrial history — a reminder of the days when every measurement was mechanical, and accuracy depended on steady hands and keen eyes.
Have you ever come across one of these before, or used one in the shop? It’s fascinating how something so simple could be so vital to keeping engines and machines running smoothly.
